Keysight Technologies N5511A User Manual

Keysight N5511A
Phase Noise Test System

User’s
Guide

Notices

© Keysight Technologies, Inc. 2019

No part of this manual may be
reproduced in any form or by any
means (including electronic storage
and retrieval or translation into a
foreign language) without prior
agreement and written consent from
Keysight Technologies, Inc. as
governed by United States and
international copyright laws.

Trademark Acknowledgments

Manual Part Number

N5511-90002

Edition

Edition 1, September 2019

Printed in USA/Malaysia

Published by:
Keysight Technologies

1400 Fountaingrove Parkway
Santa Rosa, CA 95403

Warranty

THE MATERIAL CONTAINED IN THIS
DOCUMENT IS PROVIDED “AS IS,”
AND IS SUBJECT TO BEING
CHANGED, WITHOUT NOTICE, IN
FUTURE EDITIONS. FURTHER, TO
THE MAXIMUM EXTENT PERMITTED
BY APPLICABLE LAW, KEYSIGHT
DISCLAIMS ALL WARRANTIES,
EITHER EXPRESS OR IMPLIED WITH
REGARD TO THIS MANUAL AND
ANY INFORMATION CONTAINED
HEREIN, INCLUDING BUT NOT
LIMITED TO THE IMPLIED
WARRANTIES OF
MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE.
KEYSIGHT SHALL NOT BE LIABLE
FOR ERRORS OR FOR INCIDENTAL
OR CONSEQUENTIAL DAMAGES IN
CONNECTION WITH THE
FURNISHING, USE, OR
PERFORMANCE OF THIS
DOCUMENT OR ANY INFORMATION
CONTAINED HEREIN. SHOULD
KEYSIGHT AND THE USER HAVE A
SEPARATE WRITTEN AGREEMENT
WITH WARRANTY TERMS
COVERING THE MATERIAL IN THIS

DOCUMENT THAT CONFLICT WITH
THESE TERMS, THE WARRANTY
TERMS IN THE SEPARATE
AGREEMENT WILL CONTROL.

Technology Licenses

The hardware and/or software
described in this document are
furnished under a license and may be
used or copied only in accordance
with the terms of such license.

U.S. Government Rights

The Software is “commercial
computer software,” as defined
by Federal Acquisition Regulation
(“FAR”) 2.101. Pursuant to FAR

12.212 and 27.405-3 and
Department of Defense FAR
Supplement (“DFARS”) 227.7202,
the U.S. government acquires
commercial computer software
under the same terms by which
the software is customarily
provided to the public.
Accordingly, Keysight provides
the Software to U.S. government
customers under its standard
commercial license, which is
embodied in its End User License
Agreement (EULA), a copy of
which can be found at

http://www.keysight.com/find/sweula

The license set forth in the EULA
represents the exclusive authority
by which the U.S. government
may use, modify, distribute, or
disclose the Software. The EULA
and the license set forth therein,
does not require or permit,
among other things, that
Keysight: (1) Furnish technical
information related to
commercial computer software
or commercial computer
software documentation that is
not customarily provided to the
public; or (2) Relinquish to, or
otherwise provide, the
government rights in excess of
these rights customarily provided
to the public to use, modify,
reproduce, release, perform,
display, or disclose commercial
computer software or
commercial computer software
documentation. No additional

government requirements
beyond those set forth in the
EULA shall apply, except to the
extent that those terms, rights, or
licenses are explicitly required
from all providers of commercial
computer software pursuant to
the FAR and the DFARS and are
set forth specifically in writing
elsewhere in the EULA. Keysight
shall be under no obligation to
update, revise or otherwise
modify the Software. With
respect to any technical data as
defined by FAR 2.101, pursuant
to FAR 12.211 and 27.404.2 and
DFARS 227.7102, the U.S.
government acquires no greater
than Limited Rights as defined in
FAR 27.401 or DFAR 227.7103-5
(c), as applicable in any technical
data.

Safety Notices

A CAUTION notice denotes a hazard. It
calls attention to an operating
procedure, practice, or the like that,
if not correctly performed or adhered
to, could result in damage to the
product or loss of important data. Do
not proceed beyond a CAUTION
notice until the indicated conditions
are fully understood and met.

A WARNING notice denotes a hazard.
It calls attention to an operating
procedure, practice, or the like that,
if not correctly performed or adhered
to, could result in personal injury or
death. Do not proceed beyond a
WARNING notice until the indicated
conditions are fully understood and
met.

Where to Find the Latest Information

Documentation is updated periodically. For the latest information about these products, including instrument software
upgrades, application information, and product information, browse to one of the following URLs, according to the name
of your product:

http://www.keysight.com/find/n5511a

To receive the latest updates by email, subscribe to Keysight Email Updates at the following URL:

http://www.keysight.com/find/MyKeysight

Information on preventing instrument damage can be found at:

www.keysight.com/find/PreventingInstrumentRepair

Is your product software up-to-date?

Periodically, Keysight releases software updates to fix known defects and incorporate product enhancements. To search
for software updates for your product, go to the Keysight Technical Support website at:

http://www.keysight.com/find/techsupport

3

4

Table of Contents

1. Getting Started

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Documentation Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Additional Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

System Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2. Introduction

Introducing the GUI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Designing to Meet Your Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Beginning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

N5511A Operation: A Guided Tour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Required equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

How to begin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Powering the System On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

To power on a racked system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Starting the Measurement Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Verify License Key is Installed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Powering the System Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Contents

3. Phase Noise Basics

What is Phase Noise? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Ideal vs Real Word Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Phase terms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4. Expanding Your Measurement Experience

GUI Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Viewing Markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Display Preferences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Omitting Spurs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Displaying the Parameter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Exporting Measurement Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Saving Measurement State. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Recall Measurement State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Measurement Preferences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Toolbar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

5. Absolute Measurement Fundamentals

The Phase-Lock-Loop Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Single Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Dual Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

The Phase-Lock Loop Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

The Capture and Drift tracking ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Peak tune range (PTR). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

N5511A Phase Noise Test System User’s Guide 5

Contents

Selecting the VCO Source. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

What Sets the Measurement Noise Floor? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

The System Noise Floor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

The Noise Level of the Reference Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Selecting a Reference (Single Channel). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Using a Similar Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Using a Signal Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Selecting a Reference (Dual Channel) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Tuning Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Estimating the Tuning Constant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Tracking Frequency Drift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Evaluating beat note drift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Changing the PTR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

The Tuning Qualifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Minimizing Injection Locking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Adding Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Increasing the PLL Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Inserting a Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

An attenuator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

An amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

Evaluating Noise Above the Small Angle Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

Determining the Phase-Lock-Loop bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Measured Beat Note . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

Single-sided Spur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Double-sided Spur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

6. Absolute Measurement Examples

Example Overviews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Input Ports. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Single Channel Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Required equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Configuring Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

Measurement Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Dual Channel (EFC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Required equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

Configuring Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Measurement Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

Dual Channel (DCFM). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

Required equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

Configuring Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

Measurement Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

6 N5511A Phase Noise Test System User’s Guide

OCXO Dual Channel Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

Required equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

Configuring Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

Measurement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

7. Residual and Additive Noise Measurement Fundamentals

What is Residual Noise? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

The noise mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

Fundamental Measurement Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

Frequency translation devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

Calibrating the Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

User entry of phase detector constant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

Measured Beat Note . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

Measured

Double-Sided Spur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

Single-Sided Spur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

Measurement Difficulties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

System connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

± DC Peak Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

Contents

8. Residual Measurement Examples

Amplifier Measurement Example - Single Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

Required equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

Configuring Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

Measurement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

Amplifier Measurement Example - Dual Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

Required equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

Configuring Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

Measurement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

9. FM Discriminator Fundamentals

The Frequency Discriminator Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

Basic theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

The discriminator transfer response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

10. FM Discriminator Measurement Examples

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

FM Discriminator Single Channel Measurement using Double-Sided Spur Calibration . . . . . . . . . . . . . . . . . . . . 225

Required Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

Determining the discriminator (delay line) length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

Define the measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

Setup considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

Making the measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

N5511A Phase Noise Test System User’s Guide 7

Contents

When the measurement is complete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

FM Discriminator Single Channel Measurement using FM Rate and Deviation Calibration . . . . . . . . . . . . . . . . . 240

Required Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

Determining the discriminator (delay line) length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

Define the measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

Setup considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

Making the measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

When the measurement is complete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

11. AM Noise Measurement Fundamentals

AM-Noise Measurement Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

Basic noise measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

Phase noise measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

Amplitude Noise Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

AM noise measurement block diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

Using an External AM Detector. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

Calibration and Measurement General Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260

User entry of phase detector constant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

Double-Sided Spur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

Single-Sided Spur. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

12. AM Noise Measurement Examples

AM Noise Measurement Examples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

Required equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

Configuring Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

Measurement Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274

13. Baseband Noise Measurement Example

Baseband Noise Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284

Baseband Noise with Test Set Measurement Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

Define Measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

New Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

14. Evaluating Your Measurement Results

Evaluating the Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290

Looking for obvious problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290

Comparing against expected data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291

Gathering More Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293

Repeating the measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293

Doing more research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293

Outputting the Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

Using a printer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

Graph of Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

Marker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

8 N5511A Phase Noise Test System User’s Guide

Omit Spurs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

Parameter summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300

Problem Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

Discontinuity in the graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

Higher noise level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303

Spurs on the graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304

15. Advanced Software Features

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308

Phase-Lock-Loop Suppression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309

PLL suppression parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310

Ignore-Out-Of-Lock Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312

PLL Suppression Verification Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

Accuracy degradation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

Blanking Frequency and Amplitude Information on the Phase Noise Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322

Security level procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322

16. Reference Graphs and Tables

Approximate System Noise Floor vs. R Port Signal Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328

Phase Noise Floor and Region of Validity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

Phase Noise Level of Various Keysight Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

Increase in Measured Noise as Ref Source Approaches DUT Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

Approximate Sensitivity of Delay Line Discriminator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

AM Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

Voltage Controlled Source Tuning Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

Tune Range of VCO for Center Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

Peak Tuning Range Required by Noise Level. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336

Phase Lock Loop Bandwidth vs. Peak Tuning Range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

Noise Floor Limits Due to Peak Tuning Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

Tuning Characteristics of Various VCO Source Options. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

Contents

17. System Specifications

System Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

Power requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

18. System Interconnections

N5511A System Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346

Making Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

Before connecting the cables to any device: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

Proper Connector Torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

Connecting a Display to your System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

N5511A Two Channel Cable Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349

System Connectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354

19. Preventive Maintenance

N5511A Phase Noise Test System User’s Guide 9

Contents

Using, Inspecting, and Cleaning RF Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358

Repeatability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358

RF Cable and Connector Care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358

Before connecting the cables to any device: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

Proper Connector Torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

Connector Wear and Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

2.92 Connector Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

Cleaning Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360

General Procedures and Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361

Connector Removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362

Instrument Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364

Standard instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364

Half-Rack-Width Instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365

Benchtop Instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366

Instrument Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367

Standard rack instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367

Half-Rack-Width instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368

Benchtop instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368

10 N5511A Phase Noise Test System User’s Guide

Contents

N5511A Phase Noise Test System User’s Guide 11

Contents

12 N5511A Phase Noise Test System User’s Guide

Keysight N5511A Phase Noise Test System

User’s Guide

1 Getting Started

“Introduction” on page 14

“Documentation Map” on page 15

“Additional Documentation” on page 16

“System Overview” on page 17

13

Introduction

Getting Started
Introduction

This guide introduces you to the Keysight N5511A Phase Noise Test System
software and hardware. It provides procedures for configuring the N5510
Phase Noise Measurement software, executing measurements, evaluating
results, and using the advanced software features. It also covers phase noise
basics and measurement fundamentals to get you started.

Use Table 1-1 on page 15 as a guide to:

— Learning about the N5511A phase noise test system

— Learning about phase noise basics and measurement fundamentals

— Using the N5511A system to make specific phase noise measurements.

In this guide you’ll also find information on system connections and
specifications, and procedures for re-installing phase-noise-specific hardware
and software in the system PC.

Installation information for your system is provided in the Keysight N5511A Phase Noise Test
System Getting Started Guide.

14 N5511A Phase Noise Test System User’s Guide

Getting Started
Documentation Map

Documentation Map

Table 1-1 N5511A user’s guide map

Learning about the N5511A
System

Chapter 1, “Getting Started”

Chapter 2, “Introduction” Chapter 3, “Phase Noise Basics”

Chapter 4, “Expanding Your
Measurement Experience”

Learning Phase Noise Basics &
Measurement Fundamentals

Chapter 5, “Absolute
Measurement Fundamentals”

Chapter 7, “Residual and Additive
Noise Measurement
Fundamentals”

Chapter 9, “FM Discriminator
Fundamentals”

Chapter 11, “AM Noise
Measurement Fundamentals”

Using the N5511A for Specific
Phase Noise Measurements

Chapter 6, “Absolute
Measurement Examples”

Chapter 8, “Residual
Measurement Examples”

Chapter 10, “FM Discriminator
Measurement Examples”

Chapter 12, “AM Noise
Measurement Examples”

Chapter 13, “Baseband Noise
Measurement Example”

Chapter 14, “Evaluating Your
Measurement Results”

Chapter 15, “Advanced
Software Features”

Chapter 17, “System
Specifications”

Chapter 18, “System
Interconnections”

Chapter 19, “Preventive
Maintenance”

Chapter 16, “Reference Graphs
and Tables”

N5511A Phase Noise Test System User’s Guide 15

Getting Started
Additional Documentation

Additional Documentation

The N5511A system documentation includes:

— Keysight N5511A Phase Noise Test System Installation Guide

— Keysight N5511A Series Phase Noise Test Systems SCPI Command

Reference

16 N5511A Phase Noise Test System User’s Guide

Getting Started
System Overview

System Overview

The Keysight N5511A Phase Noise Test System provides flexible sets of
measurements on one-port devices such as voltage controlled oscillators
(VCOs), dielectric resonator oscillators (DROs), crystal oscillators, and
synthesizers, and on two-port devices such as amplifiers and frequency
converters. The N5511A system measures absolute and residual phase noise,
and AM noise for CW and pulsed signals. It operates in the frequency range of
50 kHz to 40 GHz.

The N5511A Phase Noise Test System combines standard instruments, phase
noise measurement components, and PC software for maximum flexibility and
re-use of assets. The system PC operates under Windows 10 Professional and
controls the system through the N5510 measurement software. The N5510
software enables many stand-alone instruments to work in the system. This
stand-alone instrument architecture easily configures for various measurement
techniques, including the absolute phase noise PLL/reference-source
technique, and delay-line and FM-discriminator methods.

The N5511A system is available as a benchtop model. Due to the system’s
flexibility, the hardware in the system varies greatly with the options selected.
You may be installing instruments you already own in the system as well. A
typical N5511A system includes these components:

— N5511A PXIe chassis

— M9037A Controller with removable SSD drive with Windows 10 Professional

— Keysight N5510 Phase Noise Measurement software

— M9550A Phase Detector 1 or 2

— M9551A Data Converter

— M9300A Frequency Reference

— Microwave Power Splitter

Customer provided monitor with display port cable, keyboard, mouse, and RF
source(s).

Additional instruments may include a spectrum analyzer, oscilloscope, RF
counter, and power meter.

For detailed information on the instruments in your Keysight N5511A Phase
Noise Test System, refer to the individual instrument user guides.

N5511A Phase Noise Test System User’s Guide 17

Getting Started
System Overview

Figure 1-1 Keysight N5511A benchtop system

Figure 1-1 shows the N5511A Phase Noise Test System.

The N5511A can replace earlier Keysight E5505A phase noise systems. The
N5511A system uses a LAN or USB/GPIB port to communicate with the assets
in the system. However, the N5511A system and N5510 software are
backwards compatible with earlier E5505A systems and instruments. You may
easily integrate existing assets into your N5511A system. Figure 1-2 and Table

1-2 show the N5511A and earlier-model equivalents.

GPIB communication is done by using an 82357B GPIB to USB interface
adapter.

18 N5511A Phase Noise Test System User’s Guide

Getting Started
System Overview

Figure 1-2 Keysight E5505A system comparison to N5511A system

N5511A Phase Noise Test System User’s Guide 19

Getting Started
System Overview

Table 1-2 Equivalent system/instrument model numbers

System or Instrument Number Old Number

Phase Noise Test System N5511A E5505A

50 kHz - 40 GHz phase detector M9550A N5500A-201 50kHz - 26.5 GHz

Baseband Test Set

FFT/ Data Converter DC - 160 MHz M9551A E5505A-RHK

PC with data converter card and swept analyzer

20 N5511A Phase Noise Test System User’s Guide

Keysight N5511A Phase Noise Test System

User’s Guide

2 Introduction

“Introducing the GUI” on page 22

“Designing to Meet Your Needs” on page 24

“N5511A Operation: A Guided Tour” on page 25

“Powering the System On” on page 26

“Starting the Measurement Software” on page 27

“Powering the System Off” on page 30

21

Introduction
Introducing the GUI

Introducing the GUI

The graphical user interface (GUI) gives the user instant access to all
measurement functions, making it easy to configure a system and define or
initiate measurements. The most frequently used functions are displayed as
icons on a toolbar, allowing quick and easy access to the measurement
information.

The forms-based graphical interaction helps you define your measurement
quickly and easily. Each form tab is labeled with its content, preventing you
from getting lost in the defining process.

The system provides three default segment tables. To obtain a quick look at
your data, select the “fast” quality level. If it is important to have more
frequency resolution to separate spurious signals, use the “normal” and “high
resolution” quality levels. If you need to customize the offset range beyond the
defaults provided, tailor the measurement segment tables to meet your needs
and save them as a custom selection.

You can place up to nine markers on the data trace that can be plotted with the
measured data.

Other features include:

— Plotting data without spurs

— Tabular listing of spurs

— Plotting in alternate bandwidths

— Parameter summary

— Color printouts to any supported color printer

Figure 2-1 shows an example of the GUI.

22 N5511A Phase Noise Test System User’s Guide

Introduction
Introducing the GUI

Figure 2-1 N5510 graphical user interface (GUI)

N5511A Phase Noise Test System User’s Guide 23

Introduction
Designing to Meet Your Needs

Designing to Meet Your Needs

The N5511A Phase Noise Test System is a high performance measurement tool
that enables you to fully evaluate the noise characteristics of your electronic
instruments and components with unprecedented speed and ease. The phase
noise measurement system provides you with the flexibility needed to meet
today’s broad range of noise measurement requirements.

In order to use the phase noise system effectively, it is important that you have
a good understanding of the noise measurement you are making. This manual
is designed to help you gain that understanding and quickly progress from a
beginning user of the phase noise system to a proficient user of the system’s
basic measurement capabilities.

If you have just received your system or need help with connecting the hardware or loading
software, refer to your Keysight N5511A Phase Noise Test System Installation Guide now. Once
you have completed the installation procedures, return to “N5511A Operation: A Guided

Tour” to begin learning how to make noise measurements with the system.

Beginning

The section “N5511A Operation: A Guided Tour” contains a step-by-step
procedure for completing a phase noise measurement. This measurement
demonstration introduces system operating fundamentals for whatever type of
device you plan to measure.

Once you are familiar with the information in this chapter, you should be
prepared to start Chapter 4, “Expanding Your Measurement Experience”. After
you have completed that chapter, refer to Chapter 14, “Evaluating Your

Measurement Results” for help in analyzing and verifying your test results.

24 N5511A Phase Noise Test System User’s Guide

Introduction
N5511A Operation: A Guided Tour

N5511A Operation: A Guided Tour

This measurement demonstration introduces you to the system’s operation by
guiding you through an actual phase noise measurement.

You will be measuring the phase noise of the Keysight N5500A Phase Noise
Test Set’s low noise amplifier. (The measurement made in this demonstration is
the same measurement that is made to verify the system’s operation.)

As you step through the measurement procedures, you will soon discover that
the phase noise measurement system offers enormous flexibility for measuring
the noise characteristics of your signal sources and two-port devices.

Required equipment

The equipment shipped with this system is all that is required to complete this
demonstration. (Refer to the N5511A Phase Noise Test System Installation
Guide if you need information about setting up the hardware or installing the
software.)

How to begin

Follow the setup procedures beginning on the next page. The phase noise
measurement system displays a setup diagram that shows you the front panel
cable connections to make for this measurement.

If you need additional information about connecting instruments, refer to Chapter 18,

“System Interconnections”.

N5511A Phase Noise Test System User’s Guide 25

Introduction
Powering the System On

Powering the System On

Connect your system to an appropriate AC power source using the power cord
provided.

The N5511A system is shipped with an AC power cord appropriate for your
location.

Before applying power, make sure the AC power input and the location of the system meet the
requirements given in the Getting Started guide for your system. Failure to do so may result in
damage to the system or personal injury.

Warm-up Time: The downconverter and RF source instruments contain ovenized oscillators
which must warm up for 30 minutes to produce accurate measurements.

Standby Mode: The RF source uses a standby mode to keep the ovenized oscillator warm when
the instrument is connected (plugged in) to AC power, even when the power switch is in the off
position. To completely shut down the instrument, you must disconnect it from the AC power
supply.

The N5511A Benchtop system consists of an N5511A Phase Noise Test System
with one or two test sets installed. You must connect a monitor, keyboard, and
mouse before powering on the system.

Press the system power switch.

Figure 2-2 Power on the N5511A System

To power on a racked system

1. Press the system power switch (front, top right of the rack) to the on
position.

2. Verify that all instrument power switches are on.

3. Allow the system to warm up for 30 minutes.

26 N5511A Phase Noise Test System User’s Guide

Introduction
Starting the Measurement Software

Starting the Measurement Software

The N5510 software is pre-installed on the N5511A Phase Noise system.

Keysight Technologies, Inc. has not provided internet security software for this N5511A
Phase Noise Test System. Connecting the PC to a Local Area Network (LAN), without first
installing internet security software (firewall, virus protection, etc) puts both your PC and data at
risk. If you decide to connect the N5511A to a LAN, without first installing internet security
software, you do so at your own risk.

Keysight recommends turning on Windows updates and installing updates when available from
Microsoft.

Choose the N5510 software icon to launch the user interface.

Figure 2-3 Splash Screen

N5511A Phase Noise Test System User’s Guide 27

Introduction
Starting the Measurement Software

1. To start the program, double-click on the N5510 icon on the desktop
shortcut (shown above), or navigate to the N5510 User Interface through
the Windows start menu. Click Start > All Programs > Keysight N5510 >

N5510 User Interface.

2. When the program starts, the main N5510 measurement window appears

(see Figure 2-4). It shows the phase noise graph.

Figure 2-4 Main N5510 user interface window

28 N5511A Phase Noise Test System User’s Guide

Introduction
Starting the Measurement Software

Verify License Key is Installed

The N5511A will have the license key already installed, but if you ever need to install the license
key, use the following procedure.

3. Use the Keysight License Manager to see the license keys installed. Start
> All Programs > Keysight License Manager > Keysight License Manager

4. Verify the licenses are installed.

Figure 2-5 Keysight License Manager

N5511A Phase Noise Test System User’s Guide 29

Introduction
Powering the System Off

Powering the System Off

1. On the N5510 software menu, select File\Exit, Start icon, then shut down.
Always shut down the N5510 software before powering off the N5511A
system.

2. Use the Start menu to shut down the PC. Press the power switch on each
instrument to the off position.

If you receive error messages during the power on or off procedures, or during
operation, use the Windows event log for detailed information on the errors.

30 N5511A Phase Noise Test System User’s Guide

Keysight N5511A Phase Noise Test System

User’s Guide

3 Phase Noise Basics

“What is Phase Noise?” on page 32

“Ideal vs Real Word Signals” on page 33

“Phase terms” on page 34

31

Phase Noise Basics
What is Phase Noise?

What is Phase Noise?

Frequency stability can be defined as the degree to which an oscillating source
produces the same frequency throughout a specified period of time. Every RF
and microwave source exhibit some amount of frequency instability.

This stability can be broken down into two components:

—long-term stability

—short-term stability

Figure 3-1 Frequency Stability

Long-term stability describes the frequency variations that occur over long
time periods, expressed in parts per million per hour, day, month, or year.

Short-term stability contains all elements causing frequency changes about
the nominal frequency of less than a few seconds duration. The chapter deals
with short-term stability.

32 N5511A Phase Noise Test System User’s Guide

Phase Noise Basics
What is Phase Noise?

Ideal vs Real Word Signals

Mathematically, an ideal sine wave can be described by

Where A

=nominal amplitude, fo=nominal frequency. In the time domain, this

o

signal is a perfect sinusoidal waveform, and in the frequency domain, it is
represented by a single spectral line. See Figure 3-2.

Figure 3-2 Single Spectral Line

In practice however, there are always small, unwanted amplitude and phase
fluctuations present on the signal. An actual signal is better modeled by

Where E(t) = Amplitude fluctuations, and = randomly fluctuating phase
term, or phase noise. This randomly fluctuating phase term could be observed
on an ideal RF analyzer (one which has no sideband noise of its own) as seen in

Figure 3-3. The signal is now represented by a spread of spectral lines - both

above and below the nominal signal frequency in the form of modulation
sidebands due to the random amplitude and phase fluctuations.

Figure 3-3 Spread of Spectral Lines

N5511A Phase Noise Test System User’s Guide 33

Phase Noise Basics
What is Phase Noise?

Phase terms

There are two types of fluctuating phase terms:

—spurious signals

— phase noise

Spurious signals

The first are discrete signals appearing as distinct components in the spectral
density plot. These signals, commonly called spurious, can be related to known
phenomena in the signal source such as power line frequency, vibration
frequencies, or mixer products.

Phase noise

The second type of phase instability is random in nature and is commonly
called phase noise. The sources of random sideband noise in an oscillator
include thermal noise, shot noise, and flicker noise. Many terms exist to
quantify the characteristic randomness of phase noise. Essentially, all methods
measure the frequency or phase deviation of the source under test in the
frequency or time domain. Since frequency and phase are related to each
other, all of these terms are also related.

Spectral density

One fundamental description of phase instability or phase noise is spectral
density of phase fluctuations on a per-Hertz basis. The term spectral density
describes the energy distribution as a continuous function, expressed in units
of variance per unit bandwidth. We can the convert rms phase fluctuations into
a spectral density by dividing by the bandwidth of the noise sideskirts:

Where BW (bandwidth is negligible with respect to any changes in .

Because phase modulation is a symmetric process (both sidebands are
identical), we need only consider one of the noise side skirts. We use the

right-hand side noise side skirt and call that . is directly related to by
a simple approximation which has generally negligible error if the modulation
sidebands are such that the total phase deviation are much less than 1 radian

<< radian).

(Δφ

pk

34 N5511A Phase Noise Test System User’s Guide

Phase Noise Basics
What is Phase Noise?

L(f)

Another useful measure of noise energy is L(f), which is then directly related to

by a simple approximation which has generally negligible error if the
modulation sidebands are such that the total phase deviation are much less
than 1 radian (Δφ

Figure 3-4 CW signal sidebands viewed in the frequency domain

<< radian).

pk

L(f) is an indirect measurement of noise energy easily related to the RF power
spectrum observed on an RF analyzer. Figure 3-5 shows that the National
Institute of Standards and Technology (NIST) defines L(f) as the ratio of the
power--at an offset (f) Hertz away from the carrier. The phase modulation
sideband is based on a per Hertz of bandwidth spectral density and or offset
frequency in one phase modulation sideband, on a per Hertz of bandwidth
spectral density and (f) equals the Fourier frequency or offset frequency.

= single sideband (SSB) phase noise to carrier ration (per Hertz)

N5511A Phase Noise Test System User’s Guide 35

Phase Noise Basics
What is Phase Noise?

Figure 3-5 Deriving L(f) from a RF analyzer display

L(f) is usually presented logarithmically as a spectral density plot of the phase
modulation sidebands in the frequency domain, expressed in dB relative to the
carrier per Hz (dBc/Hz) as shown in Figure 3-6. This chapter, except where
noted otherwise, uses the logarithmic form of L(f) as follows:

Figure 3-6 L(f) Described Logarithmically as a Function of Offset Frequency

36 N5511A Phase Noise Test System User’s Guide

Phase Noise Basics
What is Phase Noise?

Caution must be exercised when L(f) is calculated from the spectral density of
the phase fluctuations because the calculation of L(f) is dependent on

the small angle criterion. Figure 3-7, the measured phase noise of a free
running VCO described in units of L(f), illustrates the erroneous results that can
occur if the instantaneous phase modulation exceeds a small angle line.
Approaching the carrier L(f) obviously increases in error as it indicates a
relative level of +45 dBc/Hz at a 1 Hz offset (45 dB more noise power at a 1 Hz
offset in a 1 Hz bandwidth than in the total power of the signal); which is of
course invalid.

Figure 3-7 shows a 10 dB/decade line drawn over the plot, indicating a peak

phase deviation of 0.2 radians integrated over any one decade of offset
frequency. At approximately 0.2 radians the power in the higher order
sidebands of the phase modulation is still insignificant compared to the power
in the first order sideband which insures that the calculation of L(f) remains

valid. Above the line the plot of L(f) becomes increasingly invalid, and
must be used to represent the phase noise of the signal.

Figure 3-7 Region of validity of L(f)

N5511A Phase Noise Test System User’s Guide 37

Phase Noise Basics
What is Phase Noise?

38 N5511A Phase Noise Test System User’s Guide

Keysight N5511A Phase Noise Test System

User’s Guide

4 Expanding Your Measurement Experience

“GUI Features” on page 40

“Viewing Markers” on page 40

“Display Preferences” on page 41

“Omitting Spurs” on page 43

“Displaying the Parameter Summary” on page 45

“Exporting Measurement Results” on page 47

“Saving Measurement State” on page 51

“Recall Measurement State” on page 51

“Measurement Preferences” on page 52

“Toolbar” on page 53

39

Expanding Your Measurement Experience
GUI Features

GUI Features

Viewing Markers

The marker function allows you to display the exact frequency and amplitude
of any point on the results graph.

To access the marker function, on the View menu, click Markers. In the dialog
box containing Marker buttons at the bottom of the application, up to nine
markers may be added. To add a marker, click Add Marker at the bottom of
the display and to remove a highlighted marker, click the Delete Marker
button at the bottom of the display. Markers are added to the latest measured
trace on the display.

Figure 4-1 View Markers

Figure 4-2 Add/Delete Markers

40 N5511A Phase Noise Test System User’s Guide

Expanding Your Measurement Experience
GUI Features

Display Preferences

N5510 User Interface display colors are highly customizable.
Navigate to View,
allowing the ability for the user to customize the colors of various items on the
display.

Changing the noise color will affect the noise trace of the next measurement, not the currently
displayed trace.

Figure 4-3 View Display Preferences

Display Parameters. The following menu will appear

N5511A Phase Noise Test System User’s Guide 41

Expanding Your Measurement Experience
GUI Features

Figure 4-4 Display Preferences Window

42 N5511A Phase Noise Test System User’s Guide

Expanding Your Measurement Experience
GUI Features

Omitting Spurs

The Omit Spurs function plots the currently loaded results without displaying
any spurs that may be present. The ability to omit or view spurs is conditional
on the 'Mark Spurs' option under the Type and Range tab of the measurement
definition being checked.

1. On the View menu, click Display Preferences.

2. In the Display Preferences dialog box, uncheck Spurs and click OK. See

Figure 4-5.

Figure 4-5 Uncheck spurs

N5511A Phase Noise Test System User’s Guide 43

Expanding Your Measurement Experience
GUI Features

3. The graph is displayed without spurs. See Figure 4-6.

Figure 4-6 Graph displayed without spurs

4. To re-display the spurs, check Spurs in the Display Preferences dialog

box. This feature can also be accessed by right-clicking on the plot and
unselecting View Spurs. Figure 4-7 shows the graph displayed with spurs.

Figure 4-7 Graph displayed with spurs

44 N5511A Phase Noise Test System User’s Guide

Expanding Your Measurement Experience
GUI Features

Displaying the Parameter Summary

The Parameter Summary function allows you to quickly review the
measurement parameter entries that were used for this measurement. The
parameter summary data is included when you print the graph.

1. On the View menu, click Parameter Summary. See Figure 4-8.

Figure 4-8 Navigate to Parameter Summary

N5511A Phase Noise Test System User’s Guide 45

Expanding Your Measurement Experience
GUI Features

2. The Parameter Summary Notepad dialog box appears. The data can be

printed or changed using standard Notepad functionality. See Figure 4-9.

Figure 4-9 Parameter summary notepad

46 N5511A Phase Noise Test System User’s Guide

Expanding Your Measurement Experience
GUI Features

Exporting Measurement Results

The Export Measurement Results function exports data in one of three types:

— Exporting Trace Data

— Exporting Spur Data

— Exporting X-Y Data

1. To export measurement results, on the File menu, point to Export Results,

then click on either Trace Data, Spur Data, or X-Y Data. See Figure 4-10.

Figure 4-10 Export results choices

N5511A Phase Noise Test System User’s Guide 47

Expanding Your Measurement Experience
GUI Features

Exporting Trace Data

1. On the File menu, point to Export Results, then click on Trace Data. See

Figure 4-11.

Figure 4-11 Tra ce data results

48 N5511A Phase Noise Test System User’s Guide

Expanding Your Measurement Experience
GUI Features

Exporting spur data

1. On the File menu, point to Export Results, then click on Spur Data. See

Figure 4-12.

Figure 4-12 Spur data results

N5511A Phase Noise Test System User’s Guide 49

Expanding Your Measurement Experience
GUI Features

Exporting X-Y Data

1. On the File menu, point to Export Results, then click on X-Y Data. See

Figure 4-13.

Figure 4-13 X-Y data results

50 N5511A Phase Noise Test System User’s Guide

Expanding Your Measurement Experience
GUI Features

Saving Measurement State

The current measurement state can be saved as a .pnx file. This will save all of
the measurement parameters as well as the trace that is on the plot. Click File,
Save as… Select Use Title as Filename to name the file using the title of the
graph.

Figure 4-14 Saving Measurement State

Recall Measurement State

A .pnx file can be opened to recall a previously saved state. Navigate to File,
Open and browse to the state file to recall. Note, N5510 Phase Noise
Measurement Software can recall legacy files in a .pnm format as well.
Multiple .pnx files can be recalled, resulting in overlaying traces with the active
measurement parameters being those of the last recalled file.

N5511A Phase Noise Test System User’s Guide 51

Expanding Your Measurement Experience
GUI Features

Measurement Preferences

Figure 4-15 Measurement Preferences

Pause At Connection Diagram: check to skip Connection Diagram when a New
Measurement is initiated.

Don't Automatically Clear Graph: when restarting a measurement, the default
behavior is for the current trace to be cleared. To retain the trace, uncheck this
option.

Don't Automatically change Previous Graph Color: when retaining a trace, the
application defaults the previous trace to a different color to not conflict with
the new trace. To keep the previous trace color, uncheck this option.

Don't Mark Spur: spurs will not be marked as spurs.

52 N5511A Phase Noise Test System User’s Guide

Expanding Your Measurement Experience
GUI Features

Toolbar

Figure 4-16 Toolbar selections

N5511A Phase Noise Test System User’s Guide 53

Expanding Your Measurement Experience
GUI Features

54 N5511A Phase Noise Test System User’s Guide

Keysight N5511A Phase Noise Measurement System

User’s Guide

5 Absolute Measurement Fundamentals

“The Phase-Lock-Loop Technique” on page 56

“The Phase-Lock Loop Circuit” on page 60

“What Sets the Measurement Noise Floor?” on page 63

“Selecting a Reference (Single Channel)” on page 65

“Estimating the Tuning Constant” on page 71

“Tracking Frequency Drift” on page 72

“Changing the PTR” on page 74

“Minimizing Injection Locking” on page 76

“Inserting a Device” on page 79

“Evaluating Noise Above the Small Angle Line” on page 82

“Calibration” on page 86

55

Absolute Measurement Fundamentals
The Phase-Lock-Loop Technique

The Phase-Lock-Loop Technique

Single Channel

The phase lock loop measurement technique for a single channel setup
requires two signal sources; the device-under-test and a reference source. This
measurement type requires that one of the two sources is a
voltage-controlled-oscillator (VCO).

In a PLL configuration, the reference source is locked in quadrature with the
DUT, which means that the signal from the references is 90 degrees out of
phase with the DUT. The signals from the DUT and the reference serve as the
RF and LO inputs to the phase detector. The carrier is canceled by the phase
detector, leaving only noise components in the resultant measurement.

Figure 5-1 Single Channel Phase Lock Loop

A closer look:

Figure 5-2 shows a high-level walk-through of the theory behind the single

channel PLL measurement technique.

Figure 5-2 Single Channel PLL Theory

56 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
The Phase-Lock-Loop Technique

Let the input signal from the DUT be denoted by

Let the signal from the reference be denoted by -recall the
reference is locked in quadrature.

Let the noise floor of the system be denoted by

Consider the sum and difference trigonometric formula:

1. The output of the phase detector therefore is:

2. The output of the phase detector therefore is:

Consider the small angle theorem sin(A)=A. The filtered output will be
represented as:

3. Noise contributed from the channel internally is added to the overall

output. The FFT output can be represented as a sum:

When using the PLL technique in a single channel configuration, the overall
output will include the phase noise of reference and the noise floor of the
system. If the phase noise of the DUT is better than the phase noise of the
reference, the phase noise of the reference will limit the dynamic range. If the
DUT is better than the noise floor of the system, the measurement will also not
result in the true performance of the device under test. A method to
significantly increase dynamic range is to perform a dual-channel
measurement instead of single channel.

N5511A Phase Noise Test System User’s Guide 57

Absolute Measurement Fundamentals
The Phase-Lock-Loop Technique

Dual Channel

N5511A has the option for a second phase detector module, which allows for
dual-channel cross correlation. In a dual channel setup, the DUT signal is split
to provide the input signal to each of the phase detector modules. Two
separate reference sources are required to provide a reference to each of the
phase detectors. The result of this setup is having two separate single channel
measurements with a common DUT signal, allowing for uncorrelated noise of
the two references as well as the noise contributions from the detectors to be
removed by cross-correlation.

Figure 5-3 Dual Channel Phase Lock Loop

A closer look:

Figure 5-4 shows a high-level walk-through of the theory behind the dual

channel PLL measurement technique.

Figure 5-4 Dual Channel PLL Theory

58 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
The Phase-Lock-Loop Technique

Following the logic used in a single channel measurement, the output of each
of the channels in a dual-channel, measurement can be represented as
follows:

The two outputs are cross-correlated, resulting in the phase noise of the DUT.
A dual-channel measurement removes the uncorrelated noise of the references
and the phase detectors, therefore eliminating the limiting factors in a single
channel measurement that could limit the dynamic range of the measurement.

N5511A Phase Noise Test System User’s Guide 59

Absolute Measurement Fundamentals
The Phase-Lock Loop Circuit

The Phase-Lock Loop Circuit

The Capture and Drift tracking ranges

Like other PLL circuits, the phase lock loop created for the measurement has a
Capture Range and a drift tracking range. The Capture Range is equal to 5% of
the system's peak tuning range, and the drift tracking range is equal to 24% of
the system's peak tuning range.

The system's peak tuning range is derived from the tuning characteristics of
the VCO source used for the measurement. Figure 5-5 illustrates the
relationship that typically exists between the VCO's peak-to-peak tuning range
and the tuning range of the system. The system's drift tracking range is limited
to a small portion of the peak tuning range to minimize the possibility of
measurement accuracy degradation caused by non-linearity across the VCO's

tuning range.

Peak tune range (PTR)

The peak tuning range is determined using two parameters:

— VCO tuning sensitivity (Hz/Volt)

— Total voltage tuning range (Volts)

PTR = (VCO Tuning Sensitivity) X (Total Voltage Tuning Range)

PTR = (100 Hz/V) X (10 V) = 1000 Hz

Figure 5-5 Capture and Drift-Tracking Range with Tuning Range of VCO

As an example:

A Peak Tuning Range of 1000 Hz provides the following ranges:

Capture Range = 0.05 X 1000 Hz = 50 Hz

Drift Tracking Range = 0.24 X 1000 Hz = 240 Hz

60 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
The Phase-Lock Loop Circuit

Tuning Requirements

The peak tuning range required for a measurement depends on the frequency
stability of the sources used. The signals from the sources are mixed in each of
the channel's phase detectors to create a beat note. In order for the loop to
acquire lock, the center frequencies of the sources must be close enough
together to create a beat note that is within the system's Capture Range. Once
the loop is locked, the frequency of the beat note must remain within the drift
tracking range for the duration of the measurement. In Figure 5-6, the ranges
calculated in the previous example are marked to show their relationship to the
beat note frequency.

Figure 5-6 Capture and Drift-Tracking Ranges and Beat Note Frequency

If the beat note does not remain within the drift tracking range during the
measurement, the out of lock detector is set and the System stops the
measurement. If this happens, you need to increase the system's drift tracking
range by increasing the system's peak tuning range (if possible) or by selecting
a VCO source with a greater tuning range.

N5511A Phase Noise Test System User’s Guide 61

Absolute Measurement Fundamentals
The Phase-Lock Loop Circuit

Selecting the VCO Source

Although you must select a VCO source that provides a sufficient tuning range
to permit the system to track the beat note, keep in mind that a wide tuning
range typically means a higher noise level on the VCO source signal. When the
VCO source for your measurement is also the reference source, this trade-off
can make reference source selection the most critical aspect of your
measurement setup.

Specifying your VCO Source

When you set up your PLL measurement, you need to know four things about
the tuning characteristics of the VCO source you are using. The System
determines the VCO source's peak tuning range from these four parameters.

— Tuning Constant, estimated tuning sensitivity (Hz/V)

— Center Voltage of Tuning Range, (V)

— Tune Range of VCO, (±V)

— Input Resistance of Tuning Port, (ohms) if the tuning constant is not to be

measured.

The measurement examples in the next chapter that recommend a specific
VCO source provides you with the tuning parameters for the specified source.

62 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
What Sets the Measurement Noise Floor?

What Sets the Measurement Noise Floor?

The noise floor for your measurement is set by two things:

— The noise floor of the phase detector and low-noise amplifier (LNA)

— The noise level of the reference source you are using

The System Noise Floor

The noise floor of the system is directly related to the amplitude of the input
signal at the R input port of the system’s phase detector. Table 5- 1 shows the
amplitude ranges for the L and R ports.

Table 5-1 Amplitude ranges for L and R ports

Phase Detector

50 kHz to 1.6 GHz

Ref Input

(L Port)

+ 15 dBm

to

+ 23 dBm

a. Phase noise test set Options 001 and 201 with no attenuation.
b. Phase noise test set Option 001 with no attenuation.

Signal Input

(R Port)

0 dBm

to

+ 23 dBm

1.2 to 26.5 GHz

Ref Input

(L Port)

+ 7 dBm

to

+ 10 dBm

If the L port (Reference Input) signal is within the amplitude range shown in

Table 5-1, the signal level at the R (Signal Input) port sets the noise floor for

the system.

a

Signal Input

(R Port)

0 dBm

to

+ 5 dBm

50 kHz to 26.5 GHz

AM Noise

0 dBm

to

20 dBm

b

N5511A Phase Noise Test System User’s Guide 63

Absolute Measurement Fundamentals
What Sets the Measurement Noise Floor?

Figure 5-7 shows the relationship between the R (signal) input level and the

system noise floor.

Figure 5-7 Relationship between the R input level and system noise floor

The Noise Level of the Reference Source

Unless it is below the system’s noise floor, the noise level of the source you are
using as the reference source sets the noise floor for the measurement. When
you set up your measurement, you want to use a reference source with a noise
level that is at or below the level of the source you are going to measure.

Figure 5-8 demonstrates that as the noise level of the reference source

approaches the noise level of the DUT, the level measured by the System
(which is the sum of all noise sources affecting the system) is increased above
the actual noise level of the DUT.

Figure 5-8 Reference source noise approaches DUT noise

64 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Selecting a Reference (Single Channel)

Selecting a Reference (Single Channel)

Selecting an appropriate reference source is critical when you are making a
phase noise measurement using the phase lock loop technique. The key to
selecting a reference source is to compare the noise level of the reference with
the expected noise level of the DUT. In general, the lower the reference
source’s noise level is below the expected noise level of the DUT the better.
(Keep in mind that you only need to be concerned about the reference source’s
noise level within the frequency offset range over which you plan to measure
the DUT.)

As shown by the graph in Figure 5-9, the further the reference source’s noise
level is below the noise level of the DUT, the less the reference source’s noise
contributes to the measurement results.

Figure 5-9 DUT noise approaches reference noise

Using a Similar Device

The test system performs best when you are able to use a device similar to the
DUT as the reference source for your PLL measurement. Of course one of the
devices must be capable of being voltage tuned by the system to do this.

To select a similar device for use as the reference source, you must establish
that the noise level of the reference source device is adequate to measure your
DUT. The Three Source Comparison technique enables you to establish the
actual noise levels of three comparable devices when two devices are available
in addition to the DUT.

If only one device is available in addition to the DUT, you can perform the
Phase Noise Using a Phase Locked Loop Measurement using these two
devices and know that the noise level of each of the devices is at least as good
as the measured results. (The measured results represent the sum of the noise
of both devices.)

Using a Signal Generator

When using a signal generator as a reference source, it is important that the
generator’s noise characteristics are adequate for measuring your device.

N5511A Phase Noise Test System User’s Guide 65

Absolute Measurement Fundamentals
Selecting a Reference (Dual Channel)

Selecting a Reference (Dual Channel)

Selecting references for a dual channel measurement can be less critical than
in a single channel setup. The one true requirement is that the references are
capable of being voltage tuned. With cross-correlation, PNTS removes any
noise that doesn't originate from the DUT and achieves an ultimate sensitivity
established by thermal phase noise at -177 dBm/Hz. However, the greater the
amount of uncorrelated noise present in the system, the more time it takes for
the system to remove it. This translates to low-performance reference sources
causing a longer measurement time if their phase noise is significantly worse
than the device being tested.

If the references are identical or better in performance than the device under
test, the N5511A measurement sensitivity starts at the DUT phase noise
performance level. This means the cross-correlation process starts out at this
sensitivity and this system sensitivity only improves as cross-correlations are
processed. This can be quantified by saying that for a 10 times increase in the
number of cross-correlations, there is a 5 dB reduction in uncorrelated noise
(and 5 dB improvement in PNTS system sensitivity). Therefore, in order to
minimize the time required to measure the DUT, references should be as good
or even better than the DUT.

User devices today often exceed the best signal generator's (or internal
references in some phase noise systems) phase noise performance. In
scenarios like this, the flexibility of N5511A allows for copies of the DUT to be
used as references in order to measure high performance devices without
taking a toll on time from cross-correlating out noise from low-performing
references. Figure 5-10, Figure 5-11, and Figure 5-11 show examples of DUTs
being measured using copies of the same high performance device as
references.

66 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Selecting a Reference (Dual Channel)

Example 1: Using a 100 MHz high-performance DUT as both REF1 and REF2
significantly reduces the number of cross-correlations - resulting in a dramatic
reduction in measurement time (~40 second to get to a -184 dBc/Hz
correlated device noise floor.

Figure 5-10 Using a 100 MHz High-Performance DUT

Example 2: Using a 9.6 GHz high-performance DUT as both REF1 and REF2
significantly reduces the number of cross-correlations - resulting in a dramatic
reduction in measurement time (~25 second to get to a -171 dBc/Hz
correlated device phase noise floor).

Figure 5-11 Using a 9.6 GHz High-Performance DUT

N5511A Phase Noise Test System User’s Guide 67

Absolute Measurement Fundamentals
Selecting a Reference (Dual Channel)

Example 3: Using a 10MHz high-performance DUT as both REF1 and REF2
significantly reduces the number of cross-correlations - resulting in a dramatic
reduction in measurement time (~20 minutes to get to a -60 dBc/Hz correlated
device phase noise floor at a .01 Hz offset).

Figure 5-12 Using a 10 MHz High-Performance DUT

68 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Tuning Requirements

Tuning Requirements

Often the reference source you select also serves as the VCO source for the PLL
measurement. (The VCO source can be either the DUT or the reference source.)
To configure a PLL measurement, you need to know the following tuning
information about the VCO source you are using.

— Tuning Constant (Hz/V) (within a factor of 2)

— Tuning Voltage Range (V)

— Center Voltage of Tuning Range (V)

— Input Resistance of Tuning Port (W)

The primary consideration when evaluating a potential VCO source for your
measurement is whether it provides the test system with sufficient capture and
drift tracking ranges to maintain lock throughout the measurement. To make
this determination, you must estimate what the drift range of the sources you
are using will be over the measurement period (thirty minutes maximum).
(Details on the relationship between the capture and drift tracking ranges and
the tuning range of the VCO source are provided in Table 5-2. This information
helps you evaluate your VCO source based on the estimated drift of your
sources.)

Table 5-2 lists the tuning parameters for several VCO options.

Table 5-2 Tuning Characteristics of Various VCO Source Options

VCO Source Carrier

Freq.

Agilent 8257D Measure

EFC

DCFM

Keysight 8662/3A

EFC υ

DCFM FM Deviation 0 10 1 K (8662) Compute

Keysight 8642A/B FM Deviation 0 10 600 Compute

Keysight 8644B FM Deviation 0 10 600 Compute

υ

0

υ

0

0

Tuning Constant
(Hz/V)

7 E - 8 x υ

FM Deviation 0 10 50

5 E – 9 x υ

0

0

Center
Voltage
(V)

0 10 1E + 6 Compute

010 1E + 6Measure

Voltage
Tun ing
Range (± V)

Input
Resistance
(W)

600

600 (8663) Compute

Tuning
Calibration
Method

Compute

Other Signal Generator

DCFM Calibrated for ±1V FM Deviation 0 10 Rin Compute

N5511A Phase Noise Test System User’s Guide 69

Absolute Measurement Fundamentals
Tuning Requirements

Table 5-2 Tuning Characteristics of Various VCO Source Options

VCO Source Carrier

Freq.

Other User VCO Source Estimated within a

Tuning Constant
(Hz/V)

factor of 2

Center
Voltage
(V)

–10 to
+10

Voltage
Tun ing
Range (± V)

See Figure

5-13

Input
Resistance
(W)

1 E + 6 Measure

Tuning
Calibration
Method

Figure 5-13 Voltage tuning range limits relative to center voltage of the VCO tuning curve

70 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Estimating the Tuning Constant

Estimating the Tuning Constant

The VCO tuning constant is the tuning sensitivity of the VCO source in Hz/V.
The required accuracy of the entered tuning constant value depends on the
VCO tuning constant calibration method specified for the measurement. The
calibration method is selected in the Calibration Process menu. Table 5-3 lists
the calibration method choices and the tuning constant accuracy required for
each.

Table 5-3 VCO tuning constant calibration method

VCO Tuning Constant Calibration Method
(selected in calibration screen)

Use the current tuning constant

(must be accurate from a previous
measurement of the same source).

Measure the VCO tuning constant Within a factor of 2 of actual value.

Required Tuning Constant Accuracy (entered
in parameter screen)

Within a factor of 2 of actual value.

(Enter 1 E + 6 for Input Resistance.)

(Enter 1 E + 6 for Input Resistance.)

N5511A Phase Noise Test System User’s Guide 71

Absolute Measurement Fundamentals
Tracking Frequency Drift

Tracking Frequency Drift

The system’s frequency drift tracking capability for the phase lock loop
measurement is directly related to the tuning range of the VCO source being
used. The system’s drift tracking range is approximately 24% of the peak
tuning range (PTR) of the VCO.

PTR= VCO Tuning Constant X Voltage Tuning Range

This is the frequency range within which the beat note signal created by the
test set’s phase detector must remain throughout the measurement period. In
addition, the beat note signal must remain within the system’s Capture Range
(5% of the PTR) during the time it takes the system to calibrate and lock the
phase lock loop.

The stability of the beat note is a function of the combined frequency stability
of the sources being used for the measurement. If beat note drift prevents the
beat note from remaining within the Capture Range long enough for the
system to attain phase lock, the computer informs you by displaying a
message. If the beat note drifts beyond the drift tracking range during the
measurement, the computer stops the measurement and inform you that the
system has lost lock.

72 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Tracking Frequency Drift

Evaluating beat note drift

The Checking the beat note section included in each phase lock loop
measurement example in this chapter provides a procedure for adjusting the
beat note to within the Capture Range set for the measurement. If you have not
done so already, verify that the beat note signal can be tuned to within the
Capture Range and that it will remain within the range.

Continue to observe the beat note and verify that it will not drift beyond the
drift tracking range (24% of the PTR) during the measurement period. The
length of the measurement period is primarily a function of the frequency offset
range specified for the measurement (Start to Stop Frequency).

Action

If beat note drift exceeds the limits of the Capture or drift tracking ranges set
for your measurement, the system is not able to complete the measurement.
You have two possible alternatives.

1. Minimize beat note drift.

— By Allowing sources to warm-up sufficiently.

— By Selecting a different reference source with less drift.

2. Increase the capture and drift tracking Ranges.

— By Selecting a measurement example in this chapter that specifies a

drift rate compatible with the beat note drift rate you have observed.

— By Increasing the peak tuning range for the measurement. (Further

information about increasing the PTR is provided in Changing the
PTR.)

N5511A Phase Noise Test System User’s Guide 73

Absolute Measurement Fundamentals
Changing the PTR

Changing the PTR

The peak tuning range (PTR) for the phase lock loop measurement is set by the
tune range entered for the VCO and the VCO’s tuning constant. (If the
calibration technique is set to measure the VCO tuning constant, the measured
value is used to determine the system’s PTR.)

PTR= VCO Tuning Constant X Voltage Tuning Range

From the PTR, the phase noise software derives the capture and drift tracking
Ranges for the measurement. These ranges set the frequency stability
requirements for the sources being used.

The PTR also determines the phase lock loop (PLL) bandwidth for the
measurement. An important attribute of the PLL bandwidth is that it
suppresses the close-in noise which would otherwise prevent the system from
locking the loop.

Figure 5-14 Peak tuning range

74 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Changing the PTR

The Tuning Qualifications

Changing the PTR is accomplished by changing the tune range of VCO value or
the VCO tuning constant value or both. There are several ways this can be
done. However, when considering these or any other options for changing the
PTR, it is important to remember that the VCO source must always meet the
following tuning qualifications.

— The tuning response of the VCO source must always remain monotonic.

— The VCO source’s output level must remain constant across its tuning

range.

As long as these qualifications are met, and the software does not indicate any
difficulty in establishing its calibration criteria, an increase in PTR will not
degrade the system’s measurement accuracy.

The following methods may be considered for increasing or decreasing the
PTR.

Voltage controlled oscillators

1. Select a different VCO source that has the tuning capabilities needed for

the measurement.

2. Increase the tune range of the VCO source.

Be careful not to exceed the input voltage limitations of the Tune Port on the VCO source.

Increasing the tune range of the VCO is only valid as long as the VCO source is able to
continuously meet the previously mentioned tuning qualifications.

N5511A Phase Noise Test System User’s Guide 75

Absolute Measurement Fundamentals
Minimizing Injection Locking

Minimizing Injection Locking

Injection locking occurs when a signal feeds back into an oscillator through its
output path. This can cause the oscillator to become locked to the injected
signal rather than to the reference signal for the phase locked loop.

Injection locking is possible whenever the buffering at the output of an
oscillator is not sufficient to prevent a signal from entering. If the injection
locking occurs at an offset frequency that is not well within the PLL bandwidth
set for the measurement, it can cause the system to lose phase lock.

Adding Isolation

The best way to prevent injection locking is to isolate the output of the source
being injection locked (typically the DUT) by increasing the buffering at its
output. This can be accomplished by inserting a low noise amplifier and/or an
attenuator between the output of the source being injection locked and the
test set. (Refer to “Inserting a Device” in this section.

In N5511A, one can troubleshoot isolation issues through an oscilloscope
connected to the Monitor outputs of the phase detector modules.

Figure 5-15 shows the beat notes from an absolute phase noise measurement

of a 10 MHz OCXO. Notice the impurity of the signal present at the output of
the phase detector. This reflects isolation issues. By adding isolation in each
channel, in this case by using amplifiers, the issue is improved.

Figure 5-15 Beat Notes from an Absolute Phase Noise Measurement of a 10 MHz OCXO

76 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Minimizing Injection Locking

Increasing the PLL Bandwidth

If the injection locking bandwidth is less or equal to the PLL bandwidth, it may
be possible to increase the PLL bandwidth sufficiently to complete the
measurement. The PLL bandwidth is increased by increasing the peak tuning
range (PTR) for the measurement.

The PTR for the measurement is set by the tuning characteristics of the VCO source you are
using. Figure 5-16 shows that increasing the PLL bandwidth can require a substantially larger
increase in the PTR. For information on the limitations of increasing the PTR, refer to “Changing

the PTR” in this section.

To estimate the PTR needed to prevent injection locking from causing the
system to lose lock:

1. Determine the injection locking bandwidth. Tune the beat note toward

0 Hz using the procedure described in the Checking the beat note section
of each phase lock loop measurement example in this chapter. When the
injection locking occurs, the beat note disappears. The injection locking
bandwidth is the frequency of the beat note just prior to where the
injection locking occurs as the beat note is tuned toward 0 Hz.

2. Multiply the injection locking bandwidth by 2 to determine the minimum

PLL bandwidth required to prevent the injection locking from causing the
system to lose lock. (To prevent accuracy degradation, it may be
necessary to increase the PLL bandwidth to 4 X the injection locking
bandwidth. The computer informs you during the measurement if the
possibility of accuracy degradation exists.)

3. Locate the required PLL bandwidth in Figure 5-16 to determine the PTR

required for the measurement. (For details on increasing the PTR, refer to

“Changing the PTR” in this section.

N5511A Phase Noise Test System User’s Guide 77

Absolute Measurement Fundamentals
Minimizing Injection Locking

Figure 5-16 Peak tuning range (PTR) Required by injection locking.

78 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Inserting a Device

Inserting a Device

An attenuator

You may find that some of your measurement setups require an in-line device
such as an attenuator in one of the signal source paths. (For example, you may
find it necessary to insert an attenuator at the output of a DUT to prevent it
from being injection-locked to the reference source.) The primary consideration
when inserting an attenuator is that the signal source has sufficient output
amplitude to maintain the required signal level at the test set’s phase detector
input port. The signal level required for the measurement depends on the noise
floor level needed to measure the DUT.

Figure 5-17 shows the relationship between the signal level at the R port and

the measurement noise floor.

Figure 5-17 Measurement noise floor relative to R-Port signal level

This is an important consideration in a single channel configuration. For a dual
channel configuration, equal attenuation can be placed in both channels. This
flexibility allows for cross-correlation to remove the effects of the attenuators
and recover the SNR prior to the signal of the DUT being split.

N5511A Phase Noise Test System User’s Guide 79

Absolute Measurement Fundamentals
Inserting a Device

An amplifier

If a source is not able to provide a sufficient output level, or if additional
isolation is needed at the output, it may be necessary to insert a low
phase-noise RF amplifier at the output of the source.

Note, however, that the noise of the inserted amplifier is also summed into the
measured noise level along with the noise of the source in a single channel
measurement.

Use the following equation to estimate what the measurement noise floor is as
a result of the added noise of an inserted amplifier: Figure 5-18 shows an
example.

L(f) out = –174 dB + Amplifier Noise Figure – Power into Amplifier – 3dB

Figure 5-18 Measurement noise floor as a result of an added attenuator

80 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Inserting a Device

The N5511A's dual channel cross-correlation capability offers a unique
advantage when performing measurements requiring amplifiers. In a dual
channel configuration, amplifiers of identical gain can be placed in each of the
separate channel paths. See Figure 5-19.

Figure 5-19 Dual Channel Configuration

When a measurement is configured in such manner, the noise contribution
from the amplifiers is removed by cross-correlation due to their noise being
uncorrelated. This enables the resulting noise floor measured to be the true
performance of the DUT. This technique also means that the performance of
the amplifiers need not be a critical factor; however, one must be considerate
of the impact that higher noise amplifiers will have on the number of
cross-correlations required to reach the correlated noise floor of the DUT.

N5511A Phase Noise Test System User’s Guide 81

Absolute Measurement Fundamentals
Evaluating Noise Above the Small Angle Line

Evaluating Noise Above the Small Angle Line

If the average noise level on the input signals exceeds approximately 0.1
radians RMS integrated outside of the Phase Lock Loop (PLL) bandwidth, it
can prevent the system from attaining phase lock.

The following procedure allows you to evaluate the beat note created between
the two sources being measured. The intent is to verify that the PLL bandwidth
is adequate to prevent the noise on the two sources from causing the system to
lose lock.

If the computer is displaying the hardware Connect Diagram you are ready to
begin this procedure. (If it is not, begin a New Measurement and proceed until
the hardware Connect Diagram appears on the display.)

Determining the Phase-Lock-Loop bandwidth

1. Determine the Peak Tuning Range (PTR) of your VCO by multiplying the

VCO Tuning Constant by the Tune Range of VCO value entered. (If the
phase noise software has measured the VCO Tuning Constant, use the
measured value.)

PTR = VCO Tuning Constant X Voltage Tuning

For Example:

2. Estimate the Phase Lock Loop (PLL) bandwidth for the measurement

using the PTR of your VCO and the graph in Figure 5-20.

Observing the beat note

If the beat note frequency is below 100 kHz it appears on the analyzer’s display
in both the frequency domain and the time domain. If the beat note does not
appear on the RF analyzer, then the beat note is either greater than 100 kHz or
it does not exist.

If incrementing the frequency of one of the sources does not produce a beat
note within 100 kHz, you need to verify the presence of an output signal from
each source before proceeding.

82 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Evaluating Noise Above the Small Angle Line

Figure 5-20 Phase lock loop bandwidth provided by the peak tuning range

1. Once the beat note is displayed, Auto Tune the analyzer.

2. Set the span width on the signal analyzer to approximately 4 x PLL

bandwidth. Adjust the beat note to position it near the center of the
display.

If you are not able to tune the beat note to 2 X PLL bandwidth (center of display) due to frequency
drift, refer to Tracking Frequency Drift in this section for information about measuring drifting
signals. If you are able to locate the beat note, but it distorts and then disappears as you adjust it
towards 0 Hz, then your sources are injection locking to each other. Set the beat note to the
lowest frequency possible before injection locking occurs and then refer to “Minimizing

Injection Locking” on page 76 for recommended actions.

a. Turn on trace averaging.

b. Perform Peak Search.

3. Set a Delta Marker.

On the analyzer, offset the marker by the PLL bandwidth. Read the offset
frequency and noise level indicated at the bottom of the display.

4. Compare the average noise level at the PLL bandwidth offset to the small

angle criterion level shown on the graph in Figure 5-21. The average noise
level of the signal must remain below the small angle line at all offset
frequencies beyond the PLL bandwidth. (The small angle line applies only
to the level of the average noise. Spur levels that exceed the small angle
line do not degrade measurement accuracy provided they do not exceed —
40 dBc.)

N5511A Phase Noise Test System User’s Guide 83

Absolute Measurement Fundamentals
Evaluating Noise Above the Small Angle Line

Figure 5-21 Graph of small angle line and spur limit

5. Continue moving the marker to the right to verify that the average noise

level remains below the small angle line.

6. Increase the span by a factor of ten by selecting FREQ and SPAN. Continue

comparing the noise level to the graph.

7. Continue to increase the span width and compare the noise level out to

100 kHz. (If the noise level exceeds the small angle line at any offset
frequency beyond the PLL bandwidth, note the offset frequency and level
of the noise. Use the graph in Figure 5-22 to determine the Peak Tuning
Range (PTR) necessary to provide a sufficient PLL bandwidth to make the
measurement.

Figure 5-22 Requirements for noise exceeding small angle limit

84 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Evaluating Noise Above the Small Angle Line

Measurement options

If the observed level exceeded the small angle line at any point beyond the PLL
bandwidth set for the measurement, you need to consider one of the following
measurement options.

1. Evaluate your source using the noise data provided by the RF analyzer in

the procedure you just performed.

2. Increase the PTR if possible, to provide a sufficient PLL bandwidth to

suppress the noise. (For information on increasing the PTR, refer to
Changing the PTR in this section.)

3. Reduce the noise level of the signal sources.

4. Use the Discriminator technique to measure the phase noise level of your

source.

N5511A Phase Noise Test System User’s Guide 85

Calibration

Overview

Absolute Measurement Fundamentals
Calibration

User calibrations are used to establish a reference constant for relative
measurements made on the system. For absolute measurements, the
amplitude of the carrier needs to be determined before the measurement since
the carrier is removed from the measurement when quadrature is established.
In absolute measurements various parameter of the reference need to be
measured. The type of calibration to be used is determined by the system
configuration and equipment availability. User calibrations need to be run
every time there is a change to the system or DUT parameters.

For absolute measurements, the N5511A supports four different options for
calibration, see Figure 5-23:

— Use current phase detector constant

— Derive detector constant from measured beat note

— Derive detector constant from single-sided spur

— Derive detector constant from double-sided spur

Figure 5-23 Phase Detector Calibration Options

86 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Calibration

Measured Beat Note

The measured beat note calibration method is the most common user
calibration and is the least complex. This method does not require an
additional source to set a calibration tone and is therefore the best option
when hardware is limited. The beat note frequency for each channel is set by
the relative frequency difference between the DUT and the reference in the
respective channel. If the DUT and reference are very accurate sources set at
the same frequency, the resulting beat note will be very close to 0 Hz. The
advantage is this is a simple method of calibration. The disadvantage is it

Advantages

— Simple method of calibration

Disadvantages

— Requires two RF sources, separated by 0.1 Hz to 50 MHz at the phase

detector. The calibration source output power must be manually adjusted
to the same level as the power splitter output it replaces (requires a power
meter).

Searching for the beat note will require that you adjust the center frequency of
one of the sources above and below the frequency of the other source until the
beat note appears on the oscilloscope's display. If incrementing the frequency
of one of the sources does not produce a beat note, you will need to verify the
presence of an output signal from each source before proceeding.

Theory

Recall the diagram for a single channel setup, Figure 5-24. A "beat note" is
established by shifting the frequency of the reference by 10% of the peak tune
range. This delta frequency will show up as a spur in the IF at the amplitude of
the carrier minus any losses.

The slope is measured in the linear region of the sinusoid and using the "small
angle" theorem Vpeak is determined. This value is then used to calculate the
dBc values when the phase noise is measured.

Beat note user calibration works identically in the dual channel setup, with the
only difference being that the calibration is performed separately by the
instrument for each of the phase detector modules.

N5511A Phase Noise Test System User’s Guide 87

Absolute Measurement Fundamentals
Calibration

Figure 5-24 Beat Note Single Channel

88 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Calibration

Checking the Beat Note

While the connect diagram is still displayed, use an oscilloscope (connected to
the Monitor port on the test set) or a counter to check the beat note being
created between the reference source and your DUT. The objective of checking
the beat note is to ensure that the center frequencies of the two sources are
close enough in frequency to create a beat note that is within the capture
range of the system. The phase lock loop (PLL) capture range is 5% of the peak
tuning range of the VCO source you are using. (The peak tuning range for your
VCO can be estimated by multiplying the VCO tuning constant by the tune
range of VCO. Refer to Chapter 14, “Evaluating Your Measurement Results” if
you are not familiar with the relationship between the PLL capture range and
the peak tuning range of the VCO.

If the center frequencies of the sources are not close enough to create a beat note within the
capture range, the system will not be able to complete its measurement.

The beat note frequency is set by the relative frequency difference between the
two sources. If you have two very accurate sources set at the same frequency,
the resulting beat note will be very close to 0 Hz. Searching for the beat note
will require that you adjust the center frequency of one of the sources above
and below the frequency of the other source until the beat note appears on the
oscilloscope's display. If incrementing the frequency of one of the sources does
not produce a beat note, you will need to verify the presence of an output
signal from each source before proceeding.

Figure 5-25 Oscilloscope Display of Beat Note from Test Set Monitor Port

N5511A Phase Noise Test System User’s Guide 89

Absolute Measurement Fundamentals
Calibration

Estimate the system's capture range (using the VCO source parameters
entered for this measurement). The estimated VCO tuning constant must be
accurate within a factor of 2. A procedure for “Estimating the Tuning Constant”
is located in this chapter.

If you are able to locate the beat note, but it distorts and then disappears as you adjust it towards
0 Hz, your sources are injection locking to each other. Set the beat note to the lowest frequency
possible before injection locking occurs and then refer to the “Minimizing Injection Locking”
section of this chapter for recommended actions.

If you are not able to tune the beat note to within the capture range due to frequency drift, refer to
the “Tracking Frequency Drift” section of this chapter for information about measuring
drifting signals.

90 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Calibration

Single-sided Spur

Another common calibration method is using a single-sided spur. Single-sided
spur method and double-sided spur method are the two most accurate
calibration methods. Figure 5-26 shows the setup for a measurement using the
single channel single-sided spur calibration.Figure 5-27 shows the setup for a
measurement using the dual channel single-sided spur calibration.

Figure 5-26 Single Channel SSB Cal

Figure 5-27 Dual Channel SSB Cal

N5511A Phase Noise Test System User’s Guide 91

Absolute Measurement Fundamentals
Calibration

Requirements:

— This calibration method requires a third source to generate a single sided

spur, in the case of a single channel measurement. For a dual channel
measurement, a fourth source will be required.

— An external power combiner (or directional coupler) to add the calibration

spur to the frequency carrier under test. The calibration spur must have an
amplitude -100 dB and -20 dB relative to the carrier amplitude. The offset
frequency of the spur must be 20 Hz and 20 MHz.

— A spectrum analyzer or other means to measure the single sided spur

relative to the carrier signal

The equipment setup for this calibration option is similar to the others except
that an additional source and a power splitter have been added so that the
spur can be summed with the input carrier frequency.

Advantages

— Calibration is done under actual measurement conditions so all

non-linearities and harmonics of the phase detector are calibrated out.

Disadvantages

— Requires an extra RF sources that can be set between 10 Hz and up to

50 MHz (depending on the baseband analyzer used) from the carrier source
frequency.

— Requires an RF spectrum analyzer for manual measurement of the

signal-to-spur ratio and the spur offset frequency.

For a single-sided spur user calibration, a spur is combined with the DUT
carrier. The relative amplitude of the spur is set to a convenient level. An
analyzer is typically used to measure the relative amplitude as well as offset of
the spur. The dBc value and offset is entered in the Cal tab of the Define
Measurement menu shown in Figure 5-28.

92 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Calibration

Figure 5-28 Define Measurement Menu - Cal: Known Spurs Parameters

N5511A Phase Noise Test System User’s Guide 93

Absolute Measurement Fundamentals
Calibration

The model of a single sided spur is a narrow-band PM signal summed with an
amplitude modulated signal of the same depth. The summation constructively
adds in voltage to the upper sideband in this case and destructively adds to
the lower sideband. This has the effect of increasing the upper sideband by
6 dB and eliminating the lower sideband.

Figure 5-29 Single Sided Spur

When the phase modulation is detected in the phase detector, the AM
component is rejected. This detection process reveals the lower sideband but
reduces the upper sideband by 6 dB. The software takes this into account
during the calibration process.

Figure 5-30 AM and Carrier Removal

As a result, the measured cal tone by the system will be 6 dB lower compared
to the measured amplitude by the analyzer when setting the SSB tone. Figure

5-31 shows an example of spur set to -40 dBc at a 10 kHz offset, showing how

the system will detect a -46 dBc spur.

Figure 5-31 Measured Cal Tone

94 N5511A Phase Noise Test System User’s Guide

Absolute Measurement Fundamentals
Calibration

Double-sided Spur

The double-sided spur method, along with single-side spur is the most
accurate user calibration. This calibration method conveniently needs no extra
RF source, if the DUT is capable of being phase or amplitude modulated at the
carrier frequency. When performing a double-sided spur user calibration, the
calibration is done under actual measurement conditions so all non-linearities
and harmonics of the phase detector are calibrated out. The offset frequency or
modulation frequency must be between 10 Hz and the maximum (See the
table from the “Measured Beat Note” section on page 87. The resultant
sideband spurs from the phase modulation must have amplitudes that are

-100 dB and -20 dB relative to the carrier amplitude.

Advantages

— Calibration is done under actual measurement conditions so all

non-linearities and harmonics of the phase detector are calibrated out.

— No additional RF source is needed

Disadvantages

— Requires a phase modulator which operates at the desired carrier

frequency.

— Requires RF spectrum analyzer for manual measurement of

or preferably a modulation analyzer.

The double-sided spur user calibration method connection setup is the
standard absolute measurement setup shown in Figure 5-1 on page 56 and in

Figure 5-3 on page 58. Figure 5-32 shows an example of a phase modulated

carrier with the upper side band measuring -40 dBc at a 10 kHz offset.

ΦM sidebands

N5511A Phase Noise Test System User’s Guide 95

Absolute Measurement Fundamentals
Calibration

Figure 5-32 Double-Sided Spur Method

When measuring phase noise, the carrier is modulated with a known PM
depth. This value relative to the carrier as well as the modulating rate is
entered in the software under the Cal tab.

In the example in Figure 5-33, the system measures a tone at -40 dBc

Figure 5-33 Known Spur Parameters

The system is phase locked and the modulating tone measured. In this case,
the tone is a double-sideband PM tone so there is no AM to reject, so the
entered value in the application is used to determine the amplitude of the
carrier.

96 N5511A Phase Noise Test System User’s Guide

Keysight N5511A Phase Noise Measurement System

User’s Guide

6 Absolute Measurement Examples

“Example Overviews” on page 98

“Input Ports” on page 99

“Single Channel Measurement” on page 100

“Dual Channel (EFC)” on page 117

“Dual Channel (DCFM)” on page 134

“OCXO Dual Channel Measurement” on page 150

97

Absolute Measurement Examples
Example Overviews

Example Overviews

This chapter contains 6 different measurement examples to show how to
perform an absolute phase noise measurement using the N5511A Phase Noise
Test System. The guide demonstrates single channel and dual channel
absolute phase noise measurements. The following are the examples:

— Single Channel Measurement

— Dual Channel (using EFC)

— Dual Channel (using DCFM)

— Single channel measurement of an E8257D PSG UNY using beat note

user calibration method and EFC tuning mode.

— Dual channel measurement of an E8257D PSG UNY at 1 GHz using

beat note user calibration method and EFC tuning mode. The
example features the use of two other E8257D PSG UNY as
references.

— Dual channel measurement of an E8257D PSG UNY at 10 GHz using

beat note user calibration method and DCFM tuning mode. The
example features the use of two other E8257D PSG UNY as
references.

— OCXO Dual Channel Measurement

— Dual channel measurement of a 10 MHz OCXO using beat note user

calibration method and EFC tuning mode. Example features the two
copies of DUT as references.

98 N5511A Phase Noise Test System User’s Guide

Input Ports

Absolute Measurement Examples
Input Ports

The N5511A Phase Noise Tests System phase detector frequency specification
are the following.

Carrier frequency
range

RF input power
LO input power

Low Frequency Inputs
(SMA)
All Options

50 kHz to 3 GHz 1.2 GHz to 26.5 GHz 1.2 GHz to 40 GHz 50 kHz to 40 GHz

0 dBm to +23 dBm
+15 dBm to +23 dBm

High Frequency Inputs
(Type K)
Option 526

0 dBm to +15 dBm
+7 dBm to +15 dBm

For optimal performance, however, when performing a measurement, N5510
software defaults to detector selections that do not match the hardware
capabilities. When performing a measurement, the software default detector
selections use the following guidelines:

Low Frequency Inputs 50 kHz to 1.6 GHz

High Frequency Inputs 1.6 GHz and above

This can be overwritten by manually selecting the detector to be utilized in the
measurement setup, as long as the input signal is within the hardware
specifications of the detector input.

High Frequency Inputs
(Type K)
Option 540

0 dBm to +15 dBm
+7 dBm to +15 dBm

AM Noise Input
(SMA)
All Options

0 dBm to +30 dBm
N/A

N5511A Phase Noise Test System User’s Guide 99

Absolute Measurement Examples
Single Channel Measurement

Single Channel Measurement

A single channel measurement will be a very familiar experience on the
N5511A PNTS for those that have used the E5500 system before. In a single
channel measurement, the phase noise of the reference source will contribute
to the overall phase noise of the measurement -therefore, it is very important
to have a reference source that has much lower (better) phase noise than the
phase noise of the DUT. The basic idea is we will use one PSG signal generator
as a reference source and one PSG as the device under test (DUT).

Required equipment

— Two SMA 3.5 mm cables - ideal lengths: approximately 20 inch

—One BNC-to-BNC cable

— Two signal sources: one source acting as a DUT and the other source acting

as a reference (REF) with external frequency control (EFC) capability

— One Keysight N5511A (PNTS) Phase Noise Test Set

— One oscilloscope

— One SMB-BNC cable, or appropriate cable for connection from M9550A

monitor port to oscilloscope

Reference Source: This setup calls for a tunable reference source with the same center frequency
as the DUT. In order for the noise measurement results to accurately represent the noise of the
DUT, the noise level of the reference source should be below the expected noise level of the DUT.

100 N5511A Phase Noise Test System User’s Guide