HP 11729c schematic

A

USER'S

GUIDE FOR AUTOMATIC

PHASE NOISE MEASUREMENTS

tflSES5S Product Note 11729C-3

For Complete

Application & Sales

Information

Call

Frank Engstrom

Sales Representative

HEWLETT PACKARD

NEELY

Sales Region

8080 POINTE PARKWAY WEST

PHOENIX. AZ 85044

[phone]

NOTICE

The information contained in this document is

subject to change without notice.

HEWLETT-PACKARD MAKES NO WARRANTY OF ANY KIND
WITH REGARD TO THIS MATERIAL, INCLUDING BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY
AND FITNESS FOR A PARTICULAR PURPOSE. Hewlett-Packard shall
not be liable for errors contained herein or for incidental or consequential
damages in connection with the furnishing, performance or use of this
material.

Hewlett-Packard assumes no responsibility for the use or reliability of
ware on equipment that is not furnished by Hewlett-Packard.

This document contains proprietary information which is protected by copy­right. All rights are reserved. No part of this document may be photocopied,
reproduced or translated to another language without the prior written
consent of Hewlett-Packard Company.

Copyright © 1986 by Hewlett-Packard Company.

this

soft-

A User's Guide For Automatic
Phase Noise Measurements

Table of Contents Page

Chapter I: Introduction 5

What is EASY_j?f ? Software capabilities and limitations. Instruments

supported by the software. Measurement methods.

Chapter II: System Description 7

HP 11729B/C Carrier Noise Test Set 7
HP 8662/63A Synthesized Signal Generator 7
HP 3561A Dynamic Signal Analyzer 7
HP Technical Computers 8
Printer/Plotter 8

Chapter III: Set-Up Procedure 9

Configuring the System 9
Cabling the System 9
Driver Loading 10
Running the Main Program 11
Flowchart 11

Chapter IV: Measurement Methods Overview 13

Phase Detector Method 13

Typical System Sensitivity 13
Phase Locking Techniques 14
Loop Characterization 17

Using EASY_y; in the Phase Detector Mode 18

Loading the Main Program 18
Cabling the System 18
Specifying the Measurement Parameters for the System 19

Establishing Quadrature, Calibrating and Locking 22

Graphing the Phase Noise Data 23
The Process Data Menu 24
Frequency Discriminator Method 27

System Sensitivity and the Delay Line 28

Generating the 640 MHz Reference Signal 29

System Calibration 30

Maintaining Quadrature 30
Using EASY_J?? in the Discriminator Mode 31

Loading the Main Program 31

Specifying the Measurement Parameters 31

Generating the 640 MHz Low Noise Signal 33

Calibrating and Establishing Quadrature 33

Measure and Graph the Phase Noise Data 38

Chapter V: EASY_i? Softkey Listing 39
Chapter VI: Measurement Difficulties 42

Measured Data Appears in Error at Low Offset Frequencies 42

Beat Note Not Found 42

System Cannot Phase Lock to the Signal 42

Out of Lock Indicator Tripped 42

Incorrect Spurious Signal Level Observed 42

Noise Peaking 43

Discontinuities in the Graph 43

HP 11729 B/C Internal Misinterpretation of Quadrature Condition .. 43

3

Table of Contents (cont'd) Page

Appendix A: EASY_J?? Main Program Variables Definitions 44

Main Program Only 44

Subprogram Locations and Sizes 48
Appendix B: EASY_ J? Phase Noise Measurement Program 50
EASY_if Ordering Information 53

4

The increased focus on the spectral purity of microwave signal sources has created
a need for a measurement system that provides the high performance necessary for
R&D applications and that can be automated for production environments. The
HP 11729C Carrier Noise Test Set is the key element of a system that meets this
requirement. With appropriate companion instrumentation, phase noise measure­ments can be made on a broad range of
inexpensive, easy to use software solution that allows automatic operation of the
HP 11729B/C, along with the necessary spectrum analyzers and local oscillator, is
the subject of this product note.

sources,

from 10 MHz to 18 GHz. An

This internally modular, user-friendly software, called
make automatic phase noise measurements from 10 MHz to 18 GHz on both free­running and synthesized sources. The software implements both the Phase
Detector Method and the Delay Line Discriminator Method, and provides a plot
of the phase noise measurement in units of script-L („§?). Its drivers can also be

user-modified to control instruments other than those supported by the software.
However, it does not make 2-port or AM noise measurements, nor does it make
the necessary corrections to validate the data obtained inside the phase lock loop
bandwidth, offer a choice of units with which to display the phase noise data, or
display correct discrete signal levels. The software is not specified or warranted.
This product note is the only documentation available. It
so that enhancements can easily be user added to better match a particular
application.

EASY-i? works with:

• HP 11729 B/C: Carrier Noise Test Set

• HP 8662/8663 A: Synthesized Signal Generator

• HP 8566/8568 A/B: Spectrum Analyzer

• HP 3561A: Dynamic Signal Analyzer

All instruments are linked together via HP-IB and their functions are controlled by
a HP Series 300 or 200 technical computer. The software coordinates the
instruments during the measurement, and makes the necessary calibrations to
improve the accuracy of the results.

"EASY_Jzf,"

is

written in HP BASIC

is designed to

The user is allowed to choose between two methods for making automatic phase

noise measurements on sources: the Phase Detector Method, and Frequency

Discriminator Method.

Phase Detector Method

This method requires the HP 8662A or HP 8663A, acting as a reference source,
to be phase-locked to the device under test (DUT). Two configurations are used
for phase-locking in this method. The first technique, called Electronic Frequency

Control (or EFC), uses the phase-lock circuitry of the Carrier Noise Test Set to
directly change the frequency of the HP 8662A/63A Signal Generator's 10 MHz
crystal reference oscillator. EFC is used to make accurate measurements on low
drift sources such as synthesized sources.

The second technique, called DC-FM, uses the phase-lock circuitry of the Carrier

Noise Test Set to control the FM circuitry of the HP 8662A/63A Signal Genera-

tor. DC-FM is used for measurements on sources with a greater drift rate. (For

more information on the Phase Detector Method refer to Product Note 11729B-1,

"Phase Noise Characterization of Microwave Oscillators, Phase Detector

Method", HP Literature No. 5952-8286).

5

Frequency Discriminator Method

This method does not require a reference source to make the measurement.
However, a discriminator such as a delay line or a resonator, and a phase shifter
are needed. This technique is useful for characterizing sources with large, low rate
phase instabilities such as free-running sources. Two configurations for down­converting the test frequency are implemented in the software. The first configura­tion, uses the HP 8662A/63A for down-conversion, and provides a lower noise
floor close to the carrier. The second configuration uses the HP 11729C in stand­alone (self-oscillator) mode to generate the down-conversion frequency. This
configuration does not require an HP 8662A/63A Signal Generator for down
conversion and provides a lower broadband noise floor. (For more information on
the Frequency Discriminator Method, refer to Product Note 11729C-2, "Phase
Noise Characterization of Microwave Oscillators, Frequency Discriminator
Method", HP Literature No. 5953-6497).

This product note discusses the use of the "EASY_Jz?" program for making auto­matic phase noise measurements. Chapter II describes the instruments controlled
by the software. The set-up procedure is shown in Chapter III. Chapter IV shows
two techniques for measuring the phase noise of

technique should be applied and what the software limitations are for each tech­nique. The different software menus and softkeys are covered in Chapter V.
Finally, Chapter VI outlines some of the measurement difficulties that the user

may encounter. To order your copy of

Information section at the end of this Product Note.

"EASY_Jzf",

sources;

it explains when each

refer to the Ordering

NOTE: This product note assumes the user has had some previous experience in

making phase noise measurements and has read Product Notes HP 11729B-1 and

HP 11729C-2. Copies of these product notes may be obtained at no cost from

your local Hewlett-Packard Sales and Service Office.

6

CHAPTER

11 System Description

INSTRUMENTS SUPPORTED
BY EASY_^

HP 11729B/C Carrier Noise
Test Set

HP 8662A/63A Synthesized
Signal Generator

This section describes

1

for a

block diagram representation

This instrument provides
tion

and

phase-locking
HP 8662A/63A
of two modes
mode, a selected harmonic
HP 8662A/63A
DUT

to an

baseband.

The

HP
640 MHz SAW filter
SAW oscillator capable
this mode,

When making phase noise measurements with
8662A/63A serves
provides
down-conversion process. When using
mode, the HP 8662A/63A may be used as the calibration source
discriminator.

to

IF. A second mixer

11729C

the 640

the

fixed 640 MHz

the

instruments controlled

of

the system components.

the

down-conversion

of

the resultant

as

well as baseband signal processing.

generate

is

can

the

required IF. When using

of

the fixed 640 MHz signal from

used

as a

reference signal

also

be

used

in the HP

of

generating

MHz reference signal from

as the

voltage controlled oscillator

LO

IF

in the HP

in a

SAW "oscillator" mode.

11729C

the

signal required

of

product with

to

11729C then down-converts this

is

configured into a low-noise internal

necessary reference signal. When used

the HP

the

the HP

by the

software. Refer

the DUT signal, the phase detec-

the RF
It can be

the HP

down-convert

8662A/63A

Phase Detector Method

in the

by the HP

11729C

11729C

the

the

phase-lock-loop

11729B/C

in the SAW

to

output signal

configured

in

normal

rear panel

frequency

In

this mode,

is not

required.

for the

oscillator

for

the frequency

Figure

of

the

in one

of

the

of

the

IF to

the

in

the HP

and

HP 3561A Dynamic Signal
Analyzer and HP 8566/68
Spectrum Analyzer

Figure

1.

Instruments controlled

the software.

A/B

by

Two baseband spectrum analyzers
from

the

Carrier Noise Test Set.

HP 3561A Dynamic Signal Analyzer

rapidly produce results
the necessary frequency domain data.

For higher offset frequencies,
Analyzer
frequency
COUNT UW SIG softkeys
spectrum analyzers
range
range,
software will allow
ranging from 100 Hz
software

of 1 Hz

DUT

is

selected. This Spectrum Analyzer

of

the DUT

to 10

or any

portion

an HP

(HP

the

8566

}

by

taking time domain data

and the IF

8566/68

MHz.

The

of

it.

HP 8566/68

to

10 MHz.

or an HP

HP11729B/C

CARRIER NOISE

are

For

the

broad range

frequency when

are

pressed. The combined capabilities

A/B and HP

user

can

If

an

HP

In

8568

TEST

SET

m

HP 8662/63A

SIGNAL GENERATOR

used

to

measure the noise spectrum output

offset frequencies from 1

is

used.

For low

and

of

the

HP

is

also used

the

3561A) give

select a measurement covering

3561A

is not

available
A/B to be
order

is

required

used

for

to

make a measurement with

to be

DYNAMIC SIGNAL

HP 8566/68

SPECTRUM ANALYZER

Hz to 100

offsets,

the HP

performing

8566/68

to

measure

COUNT

the

to the

offsets from

present

in the

HP3561A

ANALYZER

kHz

3561A

an FFT to get

A/B

Spectrum

the

IF SIG or the

of

the

two

system

an

the

entire

user,

the

the

carrier

the

system.

<^

A/B

the

can

offset

HP-IB

TE

IE

HP MODEL 236A,

310A, 0R320A

TECHNICAL COMPUTER

7

216A,

IF

HP Technical Computers

The software runs on an HP 9816A (requiring the large keyboard model number
98203B) or an HP 9836A series 200 computer. It will also run on the HP 9000

Series 300 computers Model 310 and 320. The Series 300 computers must be
configured with an HP 98546A display compatibility interface. The software, on
two

5'/4-inch
memory and needs the system to be configured with BASIC 2.1, 3.0, or 4.0 with
extensions. The BASIC software with extensions, occupies 500K bytes of memory,
so a total of 1M bytes of memory is needed to run the program. The BASIC 3.0
or 4.0 binaries needed to run the program are listed below.

discs or on two single sided

3^-inch

discs, requires 450K bytes of

Printer/Plotter

NAME
GRAPH

IO
MAT
KBD

CLOCK
TRANS

ERR

HPIB

CRTA

Depending on which mass storage device you are using, select the appropriate

version of the following BASIC 3.0 binaries:

SRM

DISC
CS80

A hardcopy output of the phase noise measurement can be obtained using any
printer (with "raster dump" capability) and/or plotter supported by the HP Series
200 (models 216A and 236A) or Series 300 (models 310A and 320A) Technical
Computers.

NOTE: The instruments described above are the HP instruments controlled by the
software. The only HP instruments required to run the program are the HP

11729C Carrier Noise Test Set and an HP 8566/68 A/B Spectrum Analyzer. (If
you are using EASY_J/f in the Phase Detector Method, the HP 8662A/63A is
required to be connected to the system.) A user supplied RF spectrum analyzer,

FFT spectrum analyzer, or signal generator can be integrated into the system

provided that the necessary programming changes are made by the user in the

appropriate instrument driver. The following line identifiers are used to locate the

appropriate instrument driver (via | EDIT | line Identifier):

DESCRIPTION
Graphics

I/O

Matrix Statements
Keyboard Extensions
Clock
Transfer Statement
Error Messages
HP-IB Interface Driver
ALPHA CRT Driver

Shared Resource Mgm
Small Disc Driver
CS80 Disc Driver

IDENTIFIER
Lo_Begin

Sa_Begin
Sa856XX_Begin
Sa3561a_Begin

8

INSTRUMENT
Signal Generator

SA Interface
Spectrum Analyzer
FFT Spectrum Analyzer

FILE NAME
EL866XA

ELsaSTUBa
EL856XX
EL3561A

CHAPTER

III

Set Up Procedure

Configuring the System

Before running the program, the user must configure the HP-IB instruments con­nected to the system and controlled by the software.

After loading BASIC
Drive 0 and Disc 2 in Drive 1. Then type LOAD "ELautost" and press

EXECUTE | to load the greeting file. The start-up message gives detailed address
setting instructions for each instrument. The following is a list of the instruments
controlled by the software and the addresses they should be set to in order to run
the program:

INSTRUMENT ADDRESS
Hi-Frequency Spectrum Analyzer (HP 8566/68 A/B) 718

Low Frequency Spectrum Analyzer (HP 3561 A) 711
Local Oscillator (HP 8662/63A) 719
Carrier Noise Test Set (HP 11729C) 706*
External Plotter (HP 7470A, etc.) 705
External Printer (to dump graphics) 701

NOTE:

digit (7) is a select code used to specify the internal HP-IB interface.

*Since computer peripherals usually occupy bus addresses 0 through 7, the software will recognize the

HP 11729C Carrier Noise Test Set when this instrument is set to either address 706 (original address
with which the instrument is shipped) or an alternate address of
716 refer to the HP 11729C Operating and Service Manual.

The last two digits are used to specify the instrument address. The first

2.1,

3.0, or 4.0 and all necessary binaries, insert Disc 1 in

716.

To set your instrument address to

Cabling the System

In some cases, depending on the user's needs, some of the above instruments may
be omitted. The printer/plotter provide for the hardcopy output and are not neces­sary for the operation of the system. The LO may be omitted if another source is
used to provide for the calibration sideband in the Frequency Discriminator
Method. For users interested only in offset frequencies greater than 100 Hz and up
to 10 MHz, the HP 3561A may be omitted and the only spectrum analyzer used
will be the HP 8566/68 A/B. For users interested in the entire range of offset
frequencies, from 1 Hz to 10 MHz, both spectrum analyzers need to be provided.
The software cannot do a Microwave Signal Count if the HP 8566 is not con-

nected to the system. The Carrier Noise Test Set is required to be present in the
system at all times, regardless of the offset frequency, method chosen, or cali­bration procedure used.

Once the user decides which instruments are needed for his specific measurement,
the address setting instructions in the start-up message provide the guidance for
configuring the correct adresses.

The start-up message gives the user instructions to set up the system for the Phase
Detector Method. The program assumes this configuration exists when it guides
the user through the cabling for the discriminator method. If the Frequency Discrim-

inator Method is chosen at the Main Menu, the user is then instructed to change
the connections from the phase detector to the discriminator configuration.

Figure 2 shows the connections that should be made to set up your system for the
Phase Detector Method:

9

Figure 2. System set up for the Phase

Detector

Method;

instruments supported

by the software and connections needed.

HP 8566/68

SPECTRUM

ANALYZER

A/B

HP 3561A

DYNAMIC SIG

ANALYZER

Cabling the System

I

HP11729C

CARRIER NOISE TEST SET

DUT

1.

Connect the DUT to the HP 11729C Microwave Test Signal Input.

2.

Connect the RF Output of the HP 8662/63 A to the HP 11729C's 5

640 MHz IN

HO

MHz OUT

±10tl

HP

8662/62A

SYNTHESIZED SIG GEN

EFC

I

±llf

FMIN

5

TO

1280 MHz

RF OUTPUT

to

1280 MHz Input.

3.

Connect the HP 11729C <1 MHz Output to the HP 3561A Input (if

available).

4.

Connect the HP 11729C <10 MHz Output to the HP 8566/68 A/B RF

Input.

5.

Connect the HP 8662/63A front panel FM Input to the HP 11729C rear

panel DC-FM Output (±1V).

6. Connect the HP 8662/63A rear panel 640 MHz OUT to the HP 11729C
rear panel 640 MHz IN.

Driver Loading

7.

Connect the HP 8662/63A rear panel EFC IN to the HP 11729C rear

panel EFC Output (±10V).

All instruments (except the DUT) must be connected to the technical computer

via HP-IB cables. Remember not to exceed the IEEE-488 specifications on total

cable length: 2 meters/device up to 20 meters. Avoid long cable lengths.

Once the start-up message has been loaded press the LOAD MAIN PGM
softkey. After pressing the LOAD MAIN PGM softkey and the program

is
loaded, the software identifies the instruments that are turned on and connected to
the technical computer at the addresses previously specified. The user is then
prompted to load the subprogram drivers for those instruments into memory.
Press the LOAD SUBS softkey (K5) to automatically load the instrument's
drivers. Press the ABORT LOADING softkey (K4)

if

you only want to use the

PROCESS DATA menu.

If at a later time the user wants the program to stop using one of the instruments,
the procedure to follow

is:

turn off the instrument, press |STOP| on the technical
computer and then press |RUN|. The computer search will not find the instrument
(respond NONE OF THESE when the controller asks you what instrument is
connected at the unused instrument address) and will only use those instruments
that remained ON when |RUN| was pressed.

10

Running the Main Program

The MAIN MENU is used to set up all parameters prior to performing the test or
calibrations.

Once the program has been run and all drivers for the connected instruments have

been automatically loaded, the user is prompted to set up the specific

measurement parameters. To set up the measurement parameters, use the knob on

the HP 9836A or HP 9816A Technical Computer keyboard to move the double

arrow to the parameter that you wish to modify (you may use the t and i arrow

keys if you are using a Series 300 Technical Computer). Then press the

CHANGE PARAMS softkey-and follow the directions to enter the appropriate
information. (Refer to Figure 3 for a software flowchart.)

Figure 3. Software Flowchart

ENTEfl

DUTFREQUENCY

PRESS

COUNT

APPHOX,

I.F. SIG

START

UPDATE

RESET

S/A BW

8566/68

TO

TO

A/B)

DEFAULT VALUES

DEFAULT VALUES

CALIBRATE

(HP

!»-*-

PRESS

COUNT MW SIG

FflOlfi
NEXT
PAGE

FREQUENCY
DISCRIMINATOR
METHOD

OBTAIN APPROPRIATE

LENGTH

OF

DELAY LINE

SELECT

IF

OR

^WCAL

MEASUREMENT

PHASE
DETECTOR
DC-FM

SELECT LBWF

SELECT

FM

DEVIATION

SELECT

METHOD

~r

PHASE
DETECTOR
EFC

SELECT LBWF

-4-

11

MANUAL
LOCK

Figure 3. Software Howchart
Continued

SELECT OFFSET

START AND STOP

FREQUENCIES

SELECT PLOT RANGE

Oil AUTORANGE

SELECT APPROPRIATE
SMOOTHING FACTORS:

-NUMBER OF AVERAGES

-

WHERE TO AVERAGE

-

SMOOTHING RATIO

(FOR ANALOG S/A]

SELECT

DATA LABEL

PRESS

MEASURE NOISE*

RE-MEASURE

PROCESS DATA

CHANGE ANY OF:

■ DATE/TIME

-

DATA LABEL

-

PLOT RANGE

-

NUMBER OF AVERAGES

-

SMOOTHING

-

DIFFERENT DUT WITH

SAME PROPERTIES

1 \

PREVIOUS
PAGE

"Both calibration and measurement take place here

•>

V

12

i.n.m J ticv

IV Measurement Methods Overview

There are basically two methods of making phase noise measurements, each with
its own set of advantages and disadvantages. This software allows the user to use
either the Phase Detector Method or the Frequency Discriminator Method. The
final decision to use one or the other of the two methods depends on the charac­teristics of the device under test (DUT), the offset frequencies the user is interested
in, the availability of the necessary equipment, and the capabilities and limitations
of the software and the instruments.

THE PHASE DETECTOR
METHOD

Figure 4. Basic Phase Detector Method
implementation, using a double-balance
mixer as the phase detector.

The Phase Detector Method is sometimes called the two-source technique. In this
method, the DUT and a low noise reference source are connected to a phase de­tector at the same frequency and 90 degrees out of phase (phase quadrature) as
shown in Figure 4. The output of the phase detector is then proportional to the

combined

band spectrum analyzer.

Since the output of the phase detector is proportional to the combined noise of the
two input sources, it is necessary to use a reference source that has lower noise than
the source under test. The combination of the HP 11729C and the HP 8662A/
63A represent the lowest noise 5 MHz to 18 GHz reference source available from

HP.
works optimally with fairly stable test sources. See HP Product Note 11729B-1
"Phase Noise Characterization of Microwave Oscillators, Phase Detector Method"
for a complete discussion of this measurement technique.

phase noise of the two input sources, and can be measured on a base-

Because the two input signals must be phase locked, the phase detector method

LOW PASS

DUT £ jA

OUT /^

PHASE

PHASP A.

DETECTOR

REF V

FILTER

LNA

4>

v

BASEBAND

ANALYZER

<s>

PHASE LOCK LOOP

AND QUADRATURE

MONITOR

Typical System Sensitivity The overall sensitivity of the Phase Detector Method is shown in Figure 5. The

Phase Detector Method provides good sensitivity over the entire offset frequency
range; it can be used to measure high quality standards (good close-in noise) or
state-of-the-art free-running oscillators (good far-out noise).

13

Figure

5.

Typical HP 11729C/8662A

system noise (Phase Detector Method,

locking via EFC).

The most critical component of the Phase Detector Method is the reference source.
Since the spectrum analyzer measures the rms sum of the noise of both oscillators,
the most important criterion for choosing a reference source is that its phase noise
be less than that of the source being measured. At any given frequency offset from
the carrier, one of the source's noise will dominate.

Generally, the choice of a reference source depends on the frequency of the DUT,
the required noise performance, and whether or not the reference source must
operate as the loop VCO. The HP 11729C/8662A/63A provides the lowest noise
floor for test signals ranging from 5 MHz to 18 GHz (see Figure

6).

It also provides

the loop VCO needed for the Phase Detector Method.

Figure 6. Typical HP 11729C/8662A
system sensitivity.

Phase Locking Techniques

40

20

o

m

0

•o

-20

I-

<

E

-40

tc

m

CO

FREE-RUNNING <

VCO AT 10 GHz O

SYNTHESIZER
_AT_1J)_GHz_ £

DRO AT i

1_GHf_

10 MHz i

XTAL a.

O

K

-100

en

(/>

tn

-120

-140

-160

-180

m

-SO

-80

\

\

\

\

\

\

0.1

*

»,

CN.,,

<

^

*N.

%

*

- .>.

^ „ *-

^T^

NS.

*

HP

117;

AT 10

'3'Att

IV

-640 Ml

!9C/S66

IHz-

LOW NOISE "•
340 MHz

"s

10 100 1k 10k 100k

OFFSET FROM CARRIER (Hz)

1M

Hz

2A

***

10M

Depending on the source under test and how wide a phase-lock-loop bandwidth
will be needed to maintain the phase detector in its linear range, there are two
techniques supported by the HP 11729C and the software to phase lock. First, for
very stable sources, phase lock can be established through the electronic frequency
control (EFC) of the HP 8662A/63A internal 10 MHz reference oscillator, using
the HP 11729C +10V phase lock loop control voltage output (Figure 7). This
yields a loop holding range of 1 kHz at 10 GHz and a maximum loop bandwidth
of about 1 kHz also. The advantage of locking using EFC is lower noise, but with
narrow tuning range

(1

part in 107).

14

Figure 7. Phase locking with the HP
8662A/63A Reference Oscillator.

DUT

HP11729C

1

XN

T

PHASE
DETECTOR

•

PLL

640 MHz IN

HP S662A OPT 0C3

XG4

5T0 1280 MHz A

640 MHz OUT

*-»•

m/n

INPUT

FRONT

PANEL

RFOUT

x

FREQ CONTROL
TO XTAL ± 10V

For synthesized sources, this loop holding range would probably be sufficient.
However, for free-running sources and some stabilized sources, the drift character­istics or the rate of large phase instabilities in the source under test may be such
that larger loop holding range and loop bandwidth are required.

The second phase-lock method for maintaining quadrature at the phase detector
permits greater loop holding range and loop bandwidth. By applying the HP

11729C ±

1V

Frequency Control DC FM signal to the HP 8662A/63A DC­coupled FM input, the HP 8662/63A front panel signal acts as the loop VCO (see
Figure 8). The HP 8662A/63A has ±200 kHz maximum DC-FM deviation, and

a maximum loop bandwidth of about 50 kHz. Since the maximum obtainable HP
8662A/63A DC FM deviation is a function of output frequency and can drop as

low as 25 kHz, the obtainable Loop Holding Range (LHR) and Loop Bandwidth

(LBW) is dependent on the frequency of the source under test and the resultant IF
frequency. If in a situation where the allowable deviation is only 25 kHz and lock
cannot be established, first change the test source frequency if possible to yield a
new IF. If this cannot be done, use the Frequency Discriminator Method.

15

Figure

$.

Phase locking with the

8662A/63A DC FM input.

UP

Figure 9. Typical system noise floor at 10
GHz using the Phase Detector Method.

In general, choosing a loop VCO with more tuning range increases the system
noise. However, since it is usually noisier sources that require more loop band­width, the increased system noise typically does not limit the measurement. Figure
9 shows the effect on system noise floor of choosing either of the two phase lock
techniques described above.

20

HP 11729C/8663A

/IN EFC

HP 11729C/8662A

AN DCFM

IOC

Ik 10k 100k

OFFSET FROM CARRIER (H2)

1M

Choosing between the two locking techniques described above requires the user to
have some previous knowledge about the applicabilities and advantages of each
technique. As a "rule-of-thumb", EFC is a good choice for measuring noise on
very stable sources like frequency synthesizers. However, DC-FM provides the
larger LBW needed for maintaining lock on sources with greater drift, like
low-drift, free-running sources.

16

If the user is interested in offset frequencies very close to the carrier and the source
under test can be locked by either technique, EFC would probably be the right
choice. With the EFC technique the noise floor of the HP 8662A/63A at these
close in frequencies is lower than that obtained when locking via DC-FM. This is
exactly what is required if the phase noise of the source under test is very low at
small offsets from the carrier.

Loop Characterization

Figure 10. Typical system output of a
phase noise measurement using the
Phase Detector Method.

In the Phase Detector Method a PLL (phase lock loop) forces the VCO to track
the source under test in phase for offsets less than the bandwidth of the PLL. This
tracking results in suppression of phase noise within the loop bandwidth at the
output of the phase detector. Since no software correction is made for this effect,
the measurement data obtained is not valid for those offset frequencies less than
the loop bandwidth. A vertical line at the offset frequency corresponding to the
phase locked-loop bandwidth is added to the data plot of measurements using the
Phase Detector Method. See Figure 10.

BW NORMALIZED) * NOMINAL LOOP BW-8 kHz

0

£ -40
^>

OO
TJ

—*t

I

-160
tOO 1k 10k 100k 1M 10M

(GRID LINES IN SEQUENCE OF 1, 2, 4, 6, 8)

*

/

'<

—•*

i

'

OFFSET FREQUENCY Hz

*?

The lack of correction inside the loop bandwidth is a very important fact to take
into consideration when making phase noise measurements using this software. In

general, a wider loop bandwidth is needed when locking via DC-FM since less

stable sources need more frequency tracking. The two equations below show how
to calculate the nominal loop bandwidth when using either technique. The pro­gram computes this value and displays it both on the Main Menu and on the data
plot.

nominal EFC LBW (Hz)

11729CLBF*f

10

10

DUT

(Hz)

nominal DC-FM LBW (Hz) =

(8662 A/63 A FM Peak Deviation [Hz])*11729C LBF

1

"lb

Thus,

the loop bandwidth can be changed by varying the Lock Bandwidth Factor
(LBF) when using EFC or by varying the Lock Bandwidth Factor and varying the
peak FM deviation when locking with DC-FM. Note that changing the Lock
Bandwidth Factor changes the loop bandwidth in decade steps, while changing the
FM deviation can change the loop bandwidth in finer increments.

17

For those users interested in measuring phase noise at offset frequencies inside the

loop bandwidth, HP offers another solution. The HP 11740S Microwave Phase

Noise Measurement System is a fully specified, documented and warranted system

capable of making automatic phase noise measurements at offset frequencies

ranging from 0.02 Hz to 40 MHz. The software that runs the system performs the
necessary calculations to make the measurement data valid over the entire range
of offset frequencies.

It is also possible for the user to make the software enhancements to EASY_Jz?so
that the obtained data would be valid inside the loop bandwidth. Contact your
local HP Systems Engineer for a quotation on consultation or software enhance­ments to match your specific measurement application.

USING EASY_i?IN THE
PHASE DETECTOR MODE

Loading the Main Program

Cabling the System

This section covers the procedure for using the software when making a phase
noise measurement with the Phase Detector Method. The main steps with a brief
explanation are listed below.

In order to run EASY_J*?you must configure the system with BASIC

4.0 Turn on the controller and load BASIC 2.1, 3.0, or 4.0 with the necessary
binaries. Place Disc 1 in Drive 0 and Disc 2 in Drive 1. Type LOAD "ELautost"

and press EXECUTE . This will load the Start-up Message giving you detailed

instructions on how to cable the system. After all the instruments have been prop­erly connected, press the LOAD MAIN PGM softkey. Make sure the software

identifies all the instruments connected to the computer via HP-IB and press the
LOAD SUBS softkey to load the drivers corresponding to these instruments. After
the driver loading is done, you are ready to start your phase noise measurement.

The set up procedure for the Phase Detector Method was described earlier in
Chapter III. The necessary connections are listed below. Notice that an HP
8662 A/63 A must be connected to the system in order to use EASY_J?in the
Phase Detector mode. Refer to Figure 2 for a diagram of the set-up.

1.

Connect the DUT to the HP 11729C Microwave Test Signal Input.

2.

Connect the RF Output of the HP 8662 A/63 A to the HP 11729C 5 to

1280 MHz Input.

3.

Connect the HP 11729C <1 MHz Output to the HP 3561A Input.

2.1,

3.0, or

4.

Connect the HP 11729C <10 MHz Output to the HP 8566/68 A/B Input.

5.

Connect the HP 8662A/63A rear panel 640 MHz OUT to the HP 11729C

rear panel 640 MHz IN.

6. Connect the HP 8662A/63A front panel FM Input to the HP 11729C rear
panel DC-FM Output (±1V).

7.

Connect the HP 8662/63A rear panel EFC Input to the HP 11729C rear

panel EFC Output (+10V).

18

All instruments (except the DUT) must be turned on and connected to the
controller via HP-IB.

Specifying the Measurement
Parameters for the System

Figure 11. EASY_J*?main menu for the
HP Series 200 Technical Computer.

Once all the connected HP-IB instruments are identified by the software and the
corresponding drivers have been loaded, the user is prompted to set up the para­meters corresponding to his measurement (see Figure 11). The information the
user needs to enter before starting the measurement is described below. For the
rest of this Product Note, the words enclosed in rectangular boxes represent the
text seen on the technical computer display.

2

00

1985 09:19:46
RESET TO DEFAULT VALUES
Data Label:"MEASUREMENT OF HP 8673C AT
Device frequency = 10 GHz
METHOD: Phase Del. - EFC. (Nominal Loop BW:

117Z9C Lock BW Factor

BASEBAN0:0ffset Start Frequency

Offset Stop Frequency
Baseband HiPass Filter: ..(NOT IN USE]
Analog SA Smoothing Ratio (Res BW/Video BW)
Number of sweeps to average

==> PLOT RANGE: Plot will be scaled as shown:

Top

= —

50dBc

Bottom = —150 dBc

Use KNOB and/or select a Softkey:

==>CHANGE PARM
PROCESS DATA

COUNT /xW SIG
CAL NOISE BW

= 10

= 1 Hz

= 10

10

MHz

= 4 ..

COUNT I.F. SIG MEASURE NOISE PAUSE PROGRAM

GHz AND +13 dBm EFC LOCK"

10

Hz]

= 3

(at Sped. Analyzer)

CRT

Rev 1.0

—>

PRINTER

RESET TO DEFAULT VALUES

Figure 11a. Default value of the main
menu program.

Data Label

To set up or change any of the measurement parameters described below, use the
knob on the HP 9836A/9816A Technical Computer keyboard (or the t and 1
arrow keys on the Series 300 computers) to move the double arrow to the
parameter that you wish to modify. Then press the CHANGE PARAMS soft­key (KO) and follow the directions to enter the appropriate information.

Resets all the parameters in the main menu to their default values. See figure 11a.

20 Sep 1985 00:03:15

RESET TO DEFAULT VALUES
Data Label:(no label defined)
Device Frequency
METHOD: Phase Del.

BASEBAND: Offset Start Frequency

PLOT RANGE: Plot will be AUTO scaled

= 10

GHz

--

DC FM

..

(Nominal Loop BW:
11729C Lock BW Factor
FM Deviation = 200 KHz

Offset Stop Frequency
Baseband HiPass Filter:.. (NOT IN USE)
Analog SA Smoothing Ratio (Res BW/Video BW)
Number of sweeps to average

= 100

= 1

= 1

MHz

KHz

= 1 ..

20

KHz)

= 3

(at Spect. Analyzer]

Rev 1.0

The type of DUT, carrier frequency, serial number, and locking technique are
usually specified in the data label, but you can specify any information you desire.
The maximum number of characters allowed in the data label is 60. This label
will be displayed at the top of the phase noise graph.

19

Device Frequency

METHOD Choose the Phase Detector Method. The user is now presented with the following

11729 Lock Factor Use softkeys to select your lock bandwidth factor. When locking via EFC the

FM Deviation When locking via DC-FM, the user must provide the value of both the FM devia-

Specify the carrier frequency of the device under test.

choices to phase-lock to his source: EFC, DC-FM, or Manual Lock.
Use EFC for stable synthesized sources (LBW < 1 kHz).
Use DC-FM for stable free-running sources (LBW > 1 kHz).

Use Manual Lock to tell the program to pause after acquisition and allow you
manual set-up of phase lock. This is useful when the user is not familiar with the
characteristics of

If in doubt as to which lock technique to use, first try to lock via EFC. This results
in lower system noise floor performance. If lock cannot be established or
maintained, relock using DC-FM.

LBF determines the value of the loop bandwidth. Choose the LBF that minimizes
your loop bandwidth and still allows the sources to remain locked.

tion and the LBF by using the softkeys. The software shows the value of the
maximum allowable FM deviation for the currently specified carrier frequency.
Note that the product of the LBF and the FM deviation in Hertz divided by 1000
determines the value of the loop bandwidth. Also, changing the LBF changes the
loop bandwidth in decade steps, while changing the FM deviation can change the
loop bandwidth in smaller increments.

his

source.

BASEBAND

Offset Start Frequency Specify the offset frequency closest to the carrier that you are interested in. Use the

softkeys to make your choice. The smallest offset start frequency at which the soft-

ware can measure phase noise is 1 Hz (provided that the HP 3561A is connected

to the system). If the HP 3561A is not present, the smallest offset start frequency

will be 100 Hz.

Offset Stop Frequency Use the softkeys to specify the stop frequency of interest. The largest offset stop

frequency choice offered by the software is 10 MHz.

Baseband Hi Pass Filter The HP 3561A autoranges up on the presence of low-frequency spurs. This auto-

ranging causes discontinuities on the phase noise graph. To prevent this from hap­pening, you might choose to insert a high-pass filter at the input of the HP 3561A
Dynamic Signal Analyzer. Use this parameter to specify whether or not you would
like to insert a high-pass filter, and to select the desired high-pass filter frequency.

Analog SA Smoothing Ratio Use this softkey to specify the ratio of Resolution BW to Video BW for the HP

8566/68 A/B. The use of smoothing allows the user to resolve
gives the user hints on how to choose between the different alternatives for this
parameter.

Number of sweeps to average Some averaging is usually desired because of the random nature of

keys to choose the preferred number of sweeps to be averaged. Averaging can be

either at the controller or at the Spectrum Analyzer.

spurs.

noise.

The software

Use soft-

20

PLOT RANGE

By using the CHANGE PARAMS softkey you can modify this parameter to have

the graph auto scaled or to specify the maximum and minimum values of the verti­cal axis on the graph. Note that the maximum value should not be greater than
zero since J??(f) is not a valid unit above 0 dBc.

KO:

CHANGE PARAMS

Kl: COUNT MW SIGNAL

K2:

COUNT IF SIGNAL

K3:

MEASURE NOISE

K4:

PAUSE PROGRAM

Once all of

the

above parameters have been chosen and entered into the computer,

the user can directly use the Main Menu softkeys:

Used to modify any of the measurement parameters as explained above.

Counts the carrier frequency of the DUT on the microwave spectrum analyzer
and updates its value. This step requires the HP 8566 A/B to be connected to the
system and the DUT signal to be connected to the Spectrum Analyzer Input. If
the HP 8568 A/B is the only available spectrum analyzer, then input an
approximate

F

and do an IF count.

DUT

Updates the carrier frequency of the DUT according to the measured value of the
IF signal frequency. The menu entry of the DUT frequency must be close enough
to the real value so that the program can select the correct HP 11729C filter band
to down-convert. To measure the value of the IF, the IF Output from the HP

11729C must be connected to the HP 8566/68 A/B Spectrum Analyzer when

prompted by the program.

Starts the phase noise measurement using all current parameter settings.

Pauses the phase noise measurement program. Press |CONTINUE| to get back to
the MAIN MENU.

K5:

PROCESS DATA

K6:

CAL NOISE BW

K8:

RE-MEAS NOISE

K9:

CRT->PRINTER

Used to save the current data, do re-plots, graph more than one measurement

result on the same plot, etc.

Calibrates the resolution bandwidth of the HP 8566/68 A/B Spectrum Analyzer.

This softkey will re-measure the noise using the previous calibration and specified

parameters. Use this softkey when the test set-up has not changed and you wish to

re-measure the noise. The RE-MEASURE softkey omits the calibration step and

therefore makes the re-measuring procedure faster. The RE-MEASURE softkey

dissappears on RUN or when a non-graph parameter is changed via the Main

Menu. When between measurements, the following parameters can be modified

without suppressing the re-measure option: Date/Time, Data Label, Number of

Sweeps to Average and Plot Range.

Dumps the CRT display to the printer that is connected to the system.

After pressing any of the above softkeys, a set of instructions will appear on the

display to guide the user through any new connections that need to be made

and/or softkeys that should be selected.

21

Establishing Quadrature, In order for the software to select the proper HP 11729B/C filter band, the system

Calibrating and Locking must know the correct value of

not known within ±30 MHz, the user must do a COUNT ,uW SIGNAL or
COUNT IF SIGNAL so the software can update the carrier frequency to the new
value. To count the Microwave Signal frequency, press the COUNT /uW

SIGNAL softkey (Kl), and connect the DUT to the input of the HP 8566 A/B

Spectrum Analyzer, when prompted by the software. Then press the softkey
labeled CONNECTED and the software will use the spectrum analyzer to count
the microwave signal. Once the spectrum analyzer is done counting, a message
will be displayed on the screen showing the new value of the DUT frequency. To
count the IF press the COUNT IF SIGNAL (K2) and connect the HP 11729B/C
IF Output to the HP 8566/68 A/B RF Input. Then press the softkey labeled

CONNECTED. The IF value will be measured by the Spectrum Analyzer and

the test frequency will be updated based on the value of the IF frequency

measured. Press the ABORT softkey if you decide to leave the Main Menu device

frequency entry unchanged after doing either a /iW or an IF signal count. The

frequency update will not happen if the ABORT softkey is pressed.

Once the DUT frequency value has been updated through an IF or juW signal
count (this step is not necessary but it is strongly recommended), press the
MEASURE NOISE softkey to start the measurement. The steps followed by the
software to measure the phase noise of the DUT are described below:

Seeking the Signal In this step the software automatically tunes the front panel output signal of the

HP 8662A/63A to match the unknown IF frequency and in this way is able to

obtain phase quadrature. The signal search process can be observed on the HP
8566/68 A/B Spectrum Analyzer.

the

microwave carrier frequency. If

this

value is

Calibrating the Phase To calibrate the phase detector the software sets up a beat note by offsetting the
Detector frequency and decreasing the amplitude of the HP 8662/63A output signal. This

beat note will be displayed on the HP 8566/68 A/B or the HP 3561 A, or both in
sequence. The carrier power reference level is established automatically by placing
the beat note at the top of the screen and reading the amplitude Vb in dBm. An
HP 8566/68 A/B must be part of the system during the calibration procedure.

Locking the DUT The software checks for the lock condition of the input signals to the mixer. In

normal operation it is desired to keep the PLL bandwidth as narrow as possible to
have minimum loop noise suppression. However, if too narrow a bandwidth is

chosen, it may be very difficult for the PLL to acquire or maintain lock after the
calibration procedure. To facilitate locking the DUT, the software enables the
Loop CAPTURE feature on the HP 11729B/C. When Loop CAPTURE is
activated, a wider first-order PLL enables the two signals to acquire lock (indi­cated by a green bar on the LED display). Then when CAPTURE is disabled, the
normal second order loop is again engaged, the signals will remain in quadrature,
and a measurement can be made. If phase lock is achieved the green LED will be
illuminated in the center of the quadrature indicator (located on the left side of the
front panel of the HP 11729B/C).

22

Manual Lock At the start of the measurement, the software makes up to three attempts in each

band to re-lock the DUT to the reference source. If after the third attempt the two
sources did not remain phase locked, the user will be presented with the choice of
either aborting the measurement, doing a manual lock or having the software try
again. To lock the two sources manually, when EFC locking is being used,
proceed as follows. Press the MANUAL LOCK softkey. Hold the CAPTURE
button depressed on the HP 11729C while tuning the frequency on the HP
8662A/63A until the center green LED is illuminated on the quadrature
indicator. When the green LED is illuminated release CAPTURE. If the green
LED does not stay illuminated increase the Lock Bandwidth Factor to re-enable
lock. Once lock is achieved, press the USER LOCKED softkey to inform the
software of the new condition. The software resumes automatic control of the
instruments again and starts the phase noise measurement.

If the locking technique chosen was not EFC but DC-FM, use the following proce­dure for manually locking the two sources. Press the MANUAL LOCK softkey.
Hold CAPTURE depressed while tuning the frequency of the HP 8662/63A until
the green LED of the quadrature indicator is illuminated. If the sources drift out of
phase lock after CAPTURE is released, repeat the procedure each time increasing
the FM deviation until lock is acquired. If maximum deviation is reached and the
two sources still will not stay locked, repeat the above procedure but this time
increase the Lock Bandwidth Factor until the two sources are phase locked. Then
press the USER LOCKED softkey and the software will proceed to make the
measurement. If lock cannot be achieved, use the frequency discriminator method
to make your measurement.

Graphing the Phase Noise Data

If at any time during the measurement the sources trip out of lock, the software
will automatically try (up to three times) to regain lock. If lock cannot be
acquired, repeat the above procedure until the green LED illuminates in the center
of the quadrature indicator. The software saves the data measured before the out­of-lock condition appeared and resumes the measurement from the point where
this condition was created. Therefore, the user does not have to wait for the
software to remeasure the valid data already obtained before the sources tripped
out of

lock,

the measurement is restarted from the point of trouble and not from
the beginning. Verify that the sources remain in lock (green LED in the center of
the quadrature indicator) for the duration of the measurement.

The system measures the phase detector output in frequency segments, beginning
with the highest offset to be measured. Data is normalized, corrected and graphed
while each segment is being measured by the Spectrum Analyzers. The software
first normalizes the noise bandwidth to 1 Hz. It then adds a +2.5 dB correction
factor to the final result to compensate for the use of an analog spectrum analyzer
(HP 8566/68 A/B), and finally converts from units of S0(f) to i?(f). This +2.5
dB correction factor is not applied to those segments measured with an FFT
spectrum analyzer (HP 3561A).

23

Once the measurement has started, the user is presented with a new softkey menu.
He can choose the appropriate softkey to display on the CRT the graph that is

being generated (press VIEW GRAPHICS), the measurement parameters and

current computer operation (press VIEW MENU), or choose to have the software
automatically switch between the alpha display and the graph display (press
VIEW AUTO) when they are being updated. The user is also given the choice to
abort the test any time during the measurement (press ABORT TEST). If you
chose to install a high-pass filter at the input of the HP 3561A to avoid discontin­uities on the graph, the software will prompt you with instructions to connect and
to remove the filter when appropriate.

Once the measurement is finished the process data menu is displayed on the
screen (refer to the next section for a detailed explanation of this menu). The user
can then obtain a hardcopy output from a printer or plotter, save the data, recall
data, do re-plots or go back to the main menu to start a new measurement.

24

THE PROCESS DATA MENU

This section describes methods for obtaining a hardcopy output of the measure-

ment data from the system. It also explains how to save/recall data, replot a new

axis,

recall data from previous measurements, or change the graph title.

The PLOT menu is displayed on the CRT when you press the PROCESS DATA
softkey (K5) available to you from the Main Menu (see Figure 12a). The follow­ing list describes the softkey options that are available when using the process data
menu:

Figure 12a. Softkey menu obtained after
pressing the PROCESS DATA softkey.

KO:

RE-PLOT

K3:

SAVE DATA

Figure 12b. Softkey menu obtained after

pressing the SAVE DATA softkey.

RE PLOT
MAIN MEND

SAVE DATA
RECALL DATA

EXTERNAL PLOTS
CRT -■> PRINTER

Redraws the last measured data that is currently in memory on the computer
CRT, using the current Main Menu parameters (plot scaling, data label, band­width, etc.).

Used to save the current measurement results to a disc. After pressing this softkey
a new softkey menu is displayed (see Figure 12b) offering a choice of files in
which to store the data; the user may also specify which disc drive contains the
disk on which the data will be stored. The program shows a default disc drive,
which may be changed by the user if desired.

SAVE DATA TO DISK

Current DFile Disk Drive= : INTERNAL.4.1

Press EXIT Softkey when done...

DFile DISK=
INIT.

DISK

?

DFile CATALOG
SAVE->DFile A

REDRAW PLOT

SAVE-->DFile B

SAVE-->DFile C

EXIT
SAVE-->DFile

D

K4:

EXTERNAL PLOTS

Figure 12c. Softkey menu obtained after

pressing the EXTERNAL PLOTS
softkey.

K5:

MAIN MENU

Allows the user to plot the measurement data on the CRT or to an external
plotter. A new softkey menu is displayed on the screen (see Figure 12c) after
pressing this softkey. You may then use the softkeys to change the data file to be
plotted, the disk drive containing the data file, and the type of plotter to be used.

EXTERNALLY PLOTTING RECALLED DATA

Current Plot Device = 3."INTERNAL"

Current DFile Disk Drive

Press EXIT Softkey when done...

DFile DISK=
PLOT LAST MEAS

?

= :

INTERNAL.4.1

DFile CATALOG
PLOT DFile A

PLOT AXIS
PLOT DFile

B

PL0TTER=
PLOT DFile C

?

EXIT
PLOT DFile

D

Returns the program to the Main Menu.

25

K8:

RECALL DATA

Figure 12d. Softkey menu obtained after

pressing the RECALL DATA softkey.

Recalls measured data from a disk or from the computer memory to the CRT. A
new softkey menu is displayed (see Figure 12d) after pressing this softkey. The

new menu is used to specify the data file disc drive, the data file to be recalled,

redraw the axis or view the graph/alpha. If you want the recalled data to be
plotted on a graticule, you have to press the PLOT AXIS softkey (K2) before that
data file is recalled from the disk. Otherwise, the data will be plotted on a blank

screen and the axis, scale and title will be missing. Also, the vertical line that indi­cates the value of the Loop Bandwidth in the Phase Detector Method is omitted
for clarity when plotting recalled data. However, the value of the loop bandwidth
factor, the FM deviation and the method used are recorded by the computer, so
you can calculate the loop bandwidth value if needed. These parameters are avail­able to you when pressing the DFile CATALOG softkey.

RECALL DATA FROM DISK

K9:

CRT-->PRINTER

Current DFile Disk Drive

Press EXIT Softkey when done...

DFile DISK=

DRAW LAST MEAS

?

= :

INTERNAL.4.1

DFile CATALOG
GET DFile A

REDRAW AXIS
GET DFile

B

SEE GRAPH

GET DFile C

EXIT
GET DFile

D

Dumps the CRT display to the external HP-IB graphics printer connected to the
system.

The software allows measurement results to be shown on the computer screen, a
printer (such as the HP 2673A) or an external Hewlett-Packard Graphics Language
Plotter (such as the HP 7475A). Press the CRT~> PRINTER softkey (K9) to
dump the graphics or alpha to an external printer.

In contrast to using an external printer where the data to be printed is displayed
on the computer screen, when using an external plotter the measurement data to
be printed is not shown on the computer CRT. In order to observe the data to be
plotted prior to plotting, you must choose the computer screen (internal plotter) as

your plotter and then choose the external plotter when you are done observing the

graph. The default plotting device is the computer screen. To tell the software that

you are using an external plotter as your output device press the PROCFSS
DATA softkey (K5). Then press the EXTERNAL PLOTS softkey (K4), this will
display a new softkey menu. Choose K3 (PLOTTER = ?) softkey to specify the
type of plotter being used. You are presented with the following choices to select
from:

KO:

OTHER

K5:

705, "HPGL"

K6:

3, INTERNAL

Used to plot the measurement data with a different type of plotter or with a plotter
connected at an address different from 705. The software will ask you to enter the
type of plotter being used after this key is pressed, consult the BASIC Reference
Guide under "Plotter is" for acceptable plotter specifiers.

Select this softkey if you are using an external Hewlett-Packard Graphics
Language plotter connected at address 705. To use a plotter at a different address,
use the

KO

softkey and then enter the correct specifier and address.

Select this softkey if you want the computer screen to act as your plotting device.

26

The process data menu also allows you to add a plot of previously stored data to
your graph. For example, you may want to compare recent measurement results
with older stored data from a particular instrument. When you perform this opera­tion, the recalled data will be plotted on top of (overlayed) the data presently in
memory. The procedure to follow is described below:

1.

If you have not stored the data presently in memory, you might want to do

so if you would like to use it in future sessions. To store the data to a disc

press the SAVE DATA (K3) softkey, and use the softkeys to specify the
disc drive and the data file in wich the data is to be saved. After saving your
data the program brings you back to the PROCESS DATA menu.

2.

To overplot the old data to the new graph, press the RECALL DATA

softkey (K8) and use the new softkey menu to specify the data file to be
recalled. Don't forget to also specify the data file disc drive. After this has
been done the computer screen will display both measurement data over­layed on the same graph. If you would like to use the last measured data in
future sessions, you must save it to a disc (follow the procedure described in
step 1) before a new measurement is started or before the program is stopped.

3.

To get a print out of the new graph, press the EXIT softkey (K4) to get out

of the Recall Data menu and get back to the PROCESS DATA menu. At
the PROCESS DATA menu press the CRT->PRINTER softkey to
obtain your hardcopy output.

THE FREQUENCY
DISCRIMINATOR METHOD

The process data menu is also used to redraw the measurement data with new axis
scaling. To do this, go back to the MAIN menu, move the double arrow to point
to the "Plot will be scaled as shown" parameter, press the CHANGE PARAMS
softkey and enter the new values. Then, press the PROCESS DATA softkey to
get to the process data menu. Once the process data menu has been displayed on
the CRT, use the RE-PLOT softkey to plot your data on the new axis. You can
also vary the offset start and stop frequencies and then redraw the data on the new
axis following the same procedure.

Unlike the Phase Detector Method, the Frequency Discriminator Method does
not require a reference source locked to the source under test (see Figure 13). This
makes the Frequency Discriminator Method extremely useful for measuring
sources that are difficult to phase-lock, including sources that are microphonic or
drifting. It can also be used to measure sources with high-level close-in noise, low
far-out noise floor or high close-in spurious sidebands, conditions which can pose
serious problems for the Phase Detector Method. A wide band delay line/mixer
frequency discriminator is easy to implement using the HP 11729C Carrier Noise
Test Set and common coaxial cable. This wide band approach will be discussed in
detail. For a detailed explanation of the Frequency Discriminator Method refer to
HP product note PN 11729C-2 "Phase Noise Characterization of Microwave
Oscillators, Frequency Discriminator Method."

27

Figure 13. Basic delay line/mixer
implementation of the Frequency

Discriminator Method.

DELAY LINE

rOTLTLni

\K

BASEBAND

ANALYZER

OUT

>*Q "(gHE

I 1
I PHASE I

1 SHIFTER T

I 1

&

OUADRATURE

MONITOR

In the Frequency Discriminator Method the short-term frequency fluctuations of
the source under test are translated to baseband voltage fluctuations which are
then measured and analyzed with a spectrum analyzer. The HP 11729B/C can be

easily configured for Frequency Discriminator Method measurements of free-

running sources.

A source signal in the range of 10 MHz to 18 GHz, applied to the HP 11729C

Carrier Noise Test Set, is internally down-converted to an IF frequency using a

low noise microwave reference signal. The actual discriminator is then imple-

mented at the IF, thus avoiding any requirement for a microwave frequency dis­criminator. The HP 11729B/C IF signal is internally divided into two paths. One
path connects directly to one port of the phase detector. The other path is avail­able at the front panel as the IF OUT signal. This signal is then delayed through a
user supplied delay line, and applied to the 5- to 1280-MHz Input (the second
port of the phase detector). When the two signals at the inputs of the phase detec­tor are adjusted for phase quadrature, the baseband voltage fluctuations at the
output of the phase detector are proportional to the frequency fluctuations of the
test source.

System Sensitivity and the
Delay Line

The HP 11729B/C Carrier Noise Test Set implements the delay line/mixer fre­quency discriminator for phase noise measurements on sources from 10 MHz to

18 GHz. This section explains how the HP 11729B/C makes measurements using
the delay line/mixer Frequency Discriminator Method and provides sensitivity of
better than -140 dBc/Hz at a 1 MHz offset from the carrier. For a more detailed
explanation of the Frequency Discriminator Method refer to HP product note PN

11729C-2 "Phase Noise Characterization of Microwave Oscillators, Frequency
Discriminator Method."

A delay line/mixer used as a discriminator has typical sensitivity as shown in
Figure 14; notice that the sensitivity is a function of the delay time. The Frequency
Discriminator Method has very good broadband sensitivity; however, because of
the inherent relationship between frequency and phase, the sensitivity of the
discriminator method degrades as the square of 1/f

as

the carrier under test is
approached. Because this slope follows the phase noise characteristics of free-run­ning sources, and because this technique does not require a reference source, it is
very useful for measuring sources with large, low rate phase instabilities. But
because of its poor close-in sensitivity, it is not very useful for measuring very
stable sources close to the carrier.

28

Figure 14. Typical noise contribution
of HP 11729C/8662A (Frequency
Discriminator Method) at X-band and
typical system sensitivity using a 50 ns
delay line discriminator.

Figure 15. The HP 11729C in the stand

alone discriminator mode provides the

necessary sensitivity for phase noise

measurements on free-running sources.

10 100 1k 10k 100k

OFFSET FROM CARRIER (Hz)

1M

The system sensitivity when using the Frequency Discriminator Method is depen­dent on both the length and the attenuation of the delay line. Because the HP

11729B/C down-converts the microwave signal to an IF of

less

than 1.28 GHz,
the delay line can be common coaxial or semirigid cable. Because cable attenua­tion is frequency dependent, system sensitivity can be improved by reducing the
resulting IF out of the HP 11729B/C. This technique is only possible by tuning
the DUT frequency to be closer to the nearest comb line frequency. The reduction
of delay line attenuation translates directly into increased system sensitivity. Figure

15 shows the sensitivity of the HP 11729C implementation of the delay line fre­quency discriminator using a 100 ns RG 223 delay line. The maximum delay to
be used is determined by the highest offset frequency of interest. For example, if
measurements are desired to an offset frequency (fm) of 10 MHz, the delay must
be less than

8-

r- o

Uj CQ

<2

H

lli <
CO

a

I

"2

l/2fm =1/2(10 MHz) = 50 ns.

-20

-40

-60

2-

-80

-100

oc

-120

-140

-160
1 Hz 10 Hz 100 Hz 1 kHz 10 kHz 100 kHz 1 MHz 10 MHz

\

OFFSET FROM CARRIER (Hz)

—I

1 1—

X

X

TYPICAL FREE-fiUNNING

'-SOURCE AT 10 GHz

r

X

\

X

\

-V

100 ns

"DELAY

X

X

X

\

^X_

X~

Generating the 640 MHz
Reference Signal

The HP 11729C Carrier Noise Test Set uses a selected harmonic of a 640 MHz
low noise reference signal to down-convert test signals greater than 1280 MHz to

an IF frequency.

There are two ways to obtain this 640 MHz signal. One is to use the auxiliary 640
MHz fixed frequency output of the HP 8662A/63A Synthesized Signal Generator.
If an HP 8662A/63A is part of the measurement system, the auxiliary 640 MHz
output is an excellent low noise drive signal for the HP 11729C.

However, for a low-cost, stand-alone system, the HP 11729C (not possible with
the HP 11729B) can be configured to generate its own 640 MHz signal. A 640
MHz SAW oscillator can be created by connecting the 640 MHz output to the
640 MHz input (on rear panel of the HP 11729C) with the cable-attenuator assem­bly shipped with the HP 11729C, as indicated in Figure 16.

29

Figure 16. HP 11729C cable hookup for
640 MHz self generation.

■* ^BB» i SB «BW T

1

" r ft^iV

The 640 MHz drive signal determines the HP 11729C noise floor. Figure 17

shows the noise floor of the HP 11729C at 10 GHz when in the SAW oscillator
mode and when using the signal from the HP 8662A/63A. Note that the noise
floor for the SAW oscillator mode is lower from 70 kHz to 10 MHz, and the floor
provided by the HP 8662A/63A is lower close-in.

Figure 17. The HP 11729C noise floor
when in self oscillator mode or when
using the signal from the HP 8662A/63A.

System Calibration

-20

HP 11729C SAW OSCILLATOR
MODE AT 10GHz

-120

HP 11729C WITH HP 8662/3

UJ

-140

at

<

z

a.

-160

CO
SO

-180

en

1 Hz 10 Hz 100 Hz 1 kHz 10 kHz 100 kHz 1 MHz 10 MHz

640 MHz AT 10 GHz

fm OFFSET FROM CARRIER Hz

Usually the easiest way (and the one supported by the software) to determine the
discriminator constant Kd is to measure the system response to a known FM
signal. This can be done by introducing a single FM tone with known sideband/
carrier ratio, known modulation index, or known peak deviation. The response of
the system to this known value is used as a reference level.The signal depicted in

Figure 18 represents a carrier with a single FM tone. The modulation index /? is
kept below 0.2 so the power in the higher order sidebands is negligible. Note that
the system must remain in quadrature during calibration.

Figure 18. Carrier with a single FM tone
used as the calibration signal.

30

Often the source under test itself can be modulated to produce the calibration

signal. If not, an alternate source can be substituted for the test source. The substi-

tution method can be made either with a microwave source at the same level and
frequency as the DUT or with an RF source substituted at the IF frequency.
EASY_i?uses the HP 8662 A/63 A or a manual external source substituted at the

IF frequency as the calibration source.

Maintaining Quadrature

USING EASY_2?IN THE
DISCRIMINATOR MODE

The inputs to the phase detector must be maintained in quadrature for the duration
of the measurement. Quadrature can be observed on the red and green LED dis­play of the front panel of the HP 11729C. The phase lock loop circuitry is not
used when implementing the frequency discriminator because the DUT signal is
phase-detected against a delayed version of
tor is active and is used to ensure that quadrature is maintained.

There are several ways to establish quadrature. First, the frequency of the DUT

can be varied slightly, until quadrature is indicated on the LED display. If the

DUT frequency cannot be changed, a line stretcher or a phase shifter can be added

to the fixed delay path and adjusted until quadrature is established.

This section explains the main steps that need to be followed when using

EASY_Jz? to make an automatic phase noise measurement with the Frequency

Discriminator Method.

itself.

However, the quadrature indica-

Loading the Main Program

Specifying the Measurement
Parameters

Before running the Main Program, make sure your system has been configured

with BASIC

Then, insert Disc 1 in Drive 0 and Disc 2 in Drive 1. Load the start-up message

by typing LOAD "ELautost". Press [RUN] and then follow the instructions to

cable the system for the phase detector method and to set up the instrument

addresses. After all the instruments have been properly configured, press the

LOAD MAIN PGM softkey to load the Phase Noise Measurement Program.

After the software identifies all of the instruments connected to the computer via

HP-IB press the LOAD SUBS softkey to load the drivers corresponding to these
instruments. After this step has been completed, you are ready to start your phase
noise measurement.

After loading the drivers corresponding to the connected HP-IB instruments, you
are prompted to enter the measurement parameters that characterize your specific
measurement.

Use the knob of the HP 9836A/9816A (or the 1 and i arrow keys on the Series
300 computers) Technical Computer keyboard to move the double arrow to point

to the parameter that you wish to modify. Press the CHANGE PARAMS softkey

(K0) and follow the instructions to enter the appropriate information. Described

below is the information that you need to enter before the measurement is started

(see Figure 19).

2.1,

3.0, or 4.0 and that the necessary binaries have been loaded.

31

Figure 19. EASY_ifmain menu.

Data Label: "MEASUREMENT OF HP 8684 AT GHz USING 50ns DELAY LINE
Device Frequency = 10 GHz
METHOD: Delay Line Discriminator
BASEBAND: Offset Start Frequency

Offset Stop Frequency = 10 MHz
Baseband Hi-Pass Filter:.. (NOT IN USE)
Analog SA Smoothing Ratio (Hes. BW/Video BW)
Number of sweeps to average

==> PLOT RANGE: Plot will be scaled as shown:

Top

= 0

rJBc

Bottom = -170 dBc

Use KNOB and/or select a SoftKey:

--

(l.f. Calibration)

= 1 Hz

= 4 ..

= 3

(at Sped. Analyzer)

Data Label

Device Frequency

METHOD

DISCR:I.F. CAL

DISCRI/IWCAL

BASEBAND

==>CHANGE PARM
PROCESS DATA

COUNT /iW SIG
CAL NOISE BW

COUNT I.F. SIG

MEASURE NOISE PAUSE PROGRAM

CRT

->

PRINTER

The model number of the DUT, carrier frequency, power level, serial number, etc.
are information frequently specified in the data level. The software displays this
information at the top of the phase noise graph. The maximum number of char­acters allowed in the data label is 60.

This parameter specifies the carrier frequency of the device under test and is
entered in GHz.

Select the delay-line Frequency Discriminator Method. You are faced with two

calibration choices when using this method:

Select this option when the HP 8662A/63A is part of the system or if you are
using any other RF source for calibration.

Select this option if you are using a microwave source (covering the microwave
test frequency) for calibration.

Offset Start Frequency

Offset Stop Frequency

Baseband HiPass Filter

Use the softkeys to enter the offset frequency closest to the carrier at which you
wish to measure phase noise. The smallest offset start frequency choice offered is 1
Hz if the HP 3561A is connected to the system. If the only spectrum analyzer
available is the HP 8566/68 A/B, then the smallest offset frequency at which you
can start measuring is 100 Hz.

Use the softkeys to specify the offset frequency at which you wish to stop measur-

ing phase noise. The largest offset stop frequency choice offered is 10 MHz.

The HP 3561A autoranges on the presence of low-frequency spurs. This autorang-

ing causes discontinuities on the phase noise graph. When measuring at higher

sets,

this problem can be solved by installing a high-pass filter at the input of the

off-

HP 3561 A. Use this parameter to specify whether or not you would like to insert

a high-pass filter and to select the desired high-pass filter frequency.

32

Analog SA Smoothing Ratio Smoothing is used to allow the user to average noise and resolve spurious. Use the

softkeys to specify the ratio of Res BW/Video BW to be used for the HP
8566/68 A/B. The software gives you hints to choose between the different
alternatives for this parameter.

Number of sweeps to average Use the softkeys to enter your choice of number of sweeps to be averaged.

Because of the random nature of noise, some averaging is needed to smooth the
plot of the measured data.

PLOT RANGE

Generating the 640 MHz Low
Noise Signal

By using the CHANGE PARMS softkey you can modify this parameter to have
the graph auto scaled or to specify the maximum and minimum values of the verti­cal axis on the graph. Note that the maximum value cannot be greater than zero
since Jzf(f) is not a valid unit above 0 dBc.

After entering the above parameters, the user is presented with a choice of softkeys.
Refer to the Phase Detector Method, Chapter IV for a description of the softkey
options. Make sure you remember to update the above parameters if needed
before starting a new measurement. Read the next section before selecting the
MEASURE NOISE softkey.

The software assumes the system was initially configured for the Phase Detector
Method, which uses the 640 MHz signal from the rear panel of the HP 8662A/
63 A as the reference signal. If an HP 8662A/63 A is part of the measurement
system, proceed to "Calibrating and Establishing Quadrature".

If no HP 8662A/63A is available to the user or a lower noise floor is required at
offsets >70 kHz, the HP 11729C can be configured to generate its own 640 MHz
signal (Notice that this only applies to the HP 11729C and not to the HP 11729B).
To use the Carrier Noise Test Set in SAW oscillator mode, choose the Frequency
Discriminator Method from the Main Menu, specify all the remaining measure­ment parameters, press |STOP| on the Technical Computer and then turn off the
HP 11729C. Connect the 640 MHz Out to the 640 MHz In on the rear panel of
the HP 11729C using the cable/attenuator assembly ( PN: 11729-60096) pro­vided withthis instrument (see Figure 16). Turn on the Carrier Noise Test Set and
press RUN on the computer. You have just configured your HP 11729C to gen­erate its own 640 MHz reference signal. If all other Main Menu parameters have
been correctly entered, then you are now ready to press the MEASURE NOISE
softkey (K3).

Calibrating and Establishing
Quadrature

Step 1. Establish Quadrature

After all the measurement parameters have been specified, press the MEASURE
NOISE softkey (K3) to begin the phase noise measurement. The software will
assume the system was initially configured for the Phase Detector Method and
will guide the user from that configuration through the new connections. The
instructions given by the software to cable the system for the Discriminator
Method are explained below:

ESTABLISH QUADRATURE
(1) Connect one side ol delay line (Call this side A) to the 117Z9C IF Output.
(Z) Conned other side ol delay line (=side B) to the HP 117Z9C's 5-1280 MHz Input.
Set DOT freq. or delay line length for GREEN on the HP 117Z9C quadrature indicator.

Follow above steps & press GOT QUADrature or ABORT

33

...

Step 2. Count the Down
Converted Frequency

These connections provide the delayed IF frequency that will enter the R port of
the RF mixer to be phase detected against the nondelayed version of

itself.

Adjust

the DUT frequency or the length of the delay line until the green LED of the
quadrature indicator is illuminated. Press the GOT QUAD softkey once quadra­ture has been obtained.

COUNT DOWNCONVERTED FREQUENCY
(1) Find side B of delay line (It's connected to the HP 11729C's 5-1280 MHz Input).
(2) Connect side B of delay line to HP 8566A/B RF Input.

Press CONNECTED softkey when done, or ABORT softkey...

The purpose of this step is to make sure that the power level at the output of the
delay line is at least

—5

dBm and to determine the frequency required for calibra­tion. Note that this step requires an HP 8566/68 A/B to be connected to the
system.

Step 3. Calibration and

Measurement

Step 3.1. Using the HP
8662A/63A for Calibration

There are three calibration techniques supported by the software. The tech­nique used will be determined by the sources and equipment available to
you. The three available calibration techniques are:

1.

Using the HP 8662A/63A for calibration.

2.

Using a manually controlled RF source for calibration.

3.

Using a microwave source or the DUT (manually controlled) for calibration.

If an HP 8662A/63A Signal Generator is connected to the system, the software
will automatically find and use this instrument (when |RUN| is pressed) to
automatically generate an IF calibration signal.

If an HP 8662A/63A is not available, you can use any other RF or microwave
source with FM capability for calibration. The RF calibration source must be set
at the IF frequency (power level: —10 dBm) while the microwave source must be
tuned to the frequency of the DUT (output power level should be the same as the
DUT).

If the DUT has internal frequency modulation capabilities, it can also be

used as the calibration source.

Described below are the three different calibration techniques that are available to

you. Choose that technique which best fits your measurement needs and available

equipment.

If the HP 8662A/63A is connected to the computer via HP-IB, the software will
use this instrument to generate a signal with a single FM tone to be used as the
calibration signal. An FM rate of 1 kHz with a peak deviation of 0.2 kHz is used
to generate the calibration signal. This calibration procedure is done automatically
at the IF frequency that corresponds to the DUT frequency. The instructions that
the computer gives you to set up the HP 8662A/63A as the calibration source are
as shown below:

SET UP HP 8662A/63A AS CALIBRATOR

(1) Re-connect side B of delay line to HP 11729C's 5-1280 MHz IN.
(2) Connect the HP 8662/63A RF Output to HP 8566/68 A/B RF Input.
Press the CONNECTED softkey when done, or ABORT softkey...

34

In this step the software measures the sideband to carrier ratio of the calibration
signal. This number is internally used to calculate the final value of the discrimi­nator constant Kd.

After the CONNECTED softkey is pressed, a new set of instructions appears on
the computer screen:

MEASURE CALIBRATION SIDEBAND THRU DELAY LINE
(1) Connect HP 8662/63A RF Out to the HP 117Z9C Microwave Test Signal Input.
(2) Connect the HP 11729C <10 MHz Noise Spectrum Out to the HP 8566/68 A/B

RF Input.

Press the CONNECTED softkey when done, or ABORT softkey...

The spectrum analyzer now measures the response of the sysytem to the calibration
signal. The demodulated calibration signal will have a sharp response at the base­band frequency corresponding to the FM rate, as shown in Figure 20. The power
level of this beat note is measured and recorded by the software to calculate the
discriminator constant Kd.

After completion of the calibration routine, the following prompt and instruction
will appear on the screen.

CONFIGURE FOR DUT NOISE MEASUREMENT

(1) Re-Connect the DUT output to the HP 11729C Microwave Test Signal In.

(2) Re-adjust the DUT frequency or delay line length for quadrature
Press the GOT QUADrature softkey when done, or ABORT softkey...

if

needed.

After the above instructions have been executed the software automatically starts
the phase noise measurement. If you chose to install a high-pass filter at the input
of the HP 3561 A, the software will give you instructions on when to install and
when to remove the filter. Refer to "Measure and Graph the Phase Noise Data"
for an explanation of how to process the phase noise data obtained.

Step 3.2. Using a Manually To calibrate the discriminator (delay line/mixer) with an RF source other than the
Controlled RF Source for HP 8662A/63A, make sure that your source covers the IF frequency range. When
Calibration the phase noise program is first run, the software searches for the instruments con-

nected to the controller via HP-IB. If the HP 8662A/63A is turned off or not
present in the system, the following message will appear on the CRT:

Which source (LO) is at HP-IB address 719? (choose softkey]

Press the MANUAL LO softkey (K7) when the software asks you which instru-

ment is connected at address 719. This tells the computer that you want to have
manual control of your local oscillator (LO). Then press the MEASURE NOISE
softkey (K3) and follow the directions to cable your system for the frequency dis­criminator method and to configure your RF source to work as the calibration
source. The instructions given by the software on sequential screens are listed

below:

35

Set the LO's FM deviation for 200 Hz & press CONTinue.
Set the LO's FM rate to 1 kHz & press CONTinue.
Set the LO frequency output to the IF (the software will prompt you with a numerical

value for this frequency) & press CONTinue.
Set the LO's amplitude to —10 dBm and press CONTinue.

After completing the above instructions, the computer will prompt you with the
necessary connections to set up your manual RF source as the calibrator.

Set Up LO source as Calibrator
(1) Reconnect side B of Delay Line to HP 11729C's 5-1280 MHz IN.
(2) Connect LO source RF Output to the HP 8566/68 A/B RF Input.
Press CONNECTED softkey when done, or ABORT softkey...

In this step the software measures the sideband to carrier level of the calibration
signal. This number is internally used to calculate the value of the discriminator
constant Kd.

MEASURE CALIBRATION SIDEBAND THRU DELAY LINE
(1) Connect LO source's RF OUT to the HP 11729C's Microwave Test Signal In.
(2) Re-Connect the HP 11729C <10 MHz Noise Spectrum Out to the HP 8566/68

A/B RF Input.

Press the CONNECTED softkey when done, or ABORT softkey...

The program measures the response of the system to the calibration signal in this
step.

Before pressing the CONNECTED softkey make sure the GREEN LED is

lit on the center of the HP 11729C's quadrature indicator.

CONFIGURE FOR DUT NOISE MEASUREMENT
(1) Re-connect DUT Output to the HP 11729C's Microwave Test Signal In.
(2) Re-adjust DUT Frequency or Delay Line Length for quadrature

Press GOT QUADrature softkey when done, or ABORT softkey...

if

needed.

After all these steps have been completed, the software starts measuring and plot­ting the phase noise data. If you chose to install a high-pass filter at the input of
the HP 3561A the software will give you instructions on when to install and when
to remove the filter. The section titled "Measure and Graph the Phase Noise Data"
describes how to process and interpret the measurement data obtained.

36

Figure 20. System response to the
calibration signal.

^Pcal

i

\

- \
8^

J

V

nicaJ

\

\l

*n

uuL

# ru-»i

ksj'tyW

1

Step 3.3. Using a Substitute This is the last calibration option supported by the software. If you are using a
Microwave Source (or the
Microwave DUT) for
Calibration

microwave source other than the DUT for calibration, tune the source to the micro­wave test signal and set the power output to the DUT power level. The software
will instruct you on when and how to proceed when using a microwave source or
the microwave DUT for calibration. The instructions that need to be followed are
described below:

SET UP uW SOURCE AS CALIBRATOR

If not using DUT as calibrator, connect uW cal source to 11729C uW Test In.

(D

Set the uW Source's FM to approximately 1 kHz Deviation and 80 kHz Rate.

(2)

Set uW source's FM (above). Observe cal sideband on SA, & press softkey...

The purpose of this step is to measure the sideband to carrier ratio of the calibra-

tion signal. If the microwave calibration source is not the DUT, tune the cali-

bration source to the same frequency and amplitude as the DUT.

MEASURE CALIBRATION SIDEBAND THRU DELAY LINE
(1) Connect Delay Line Side B (now at SA input) to the HP 11729C's 5-1280 MHz IN.
(2) Reconnect the 11729C's <10 MHz Noise Spectrum Out to the HP 8566/68 A/B

RF Input.

Do the above, verify QUADrature, & then press the CONNECTED softkey (or ABORT).

The HP 8566/68 A/B spectrum analyzer measures the response of the system to
the calibration signal. Check to see that the system is operating in phase quadra­ture.

Set quadrature by adjusting the frequency of the microwave calibration

source or by adjusting the length of the delay line. The system will have a sharp

response at the frequency corresponding to the FM rate. The software measures
and records the power level of the calibration signal and uses it to calculate the
value of the discriminator constant Kd.

CONFIGURE FOR DUT NOISE MEASUREMENT
(1) Re-connect DUT to 11729C uW-lnput
(2) Re-adjust DUT Frequency or Delay Line Length for QUADrature

if

needed, and make sure its FM is OFF.

if

needed.

Press GOT QUADrature softkey when done, or ABORT softkey...

37

This is the last calibration step. If you were using a microwave calibration source
other than the DUT, disconnect the calibration source and re-connect the DUT to
the HP 11729B/C Microwave Test Signal Input. If you were using the DUT as
the calibration source, turn off the modulation and make sure the green LED is
illuminated indicating that the inputs to the phase detector are in quadrature.

After completing these steps the software starts the phase noise measurement. If
you chose to connect a filter at the input of the HP 3561 A, the software will give
instructions on when to install and when to remove the filter. Refer to the section
below for an explanation of how to process the phase noise data obtained.

Measure and Graph the Once the calibration is completed and quadrature is obtained, the phase noise
Phase Noise Data measurement starts. The data that is being measured can be observed as it is

graphed, by pressing the VIEW GRAPHICS softkey. The VIEW ALPHA soft-

key provides messages indicating the measurement step in process. The VIEW
AUTO softkey switches automatically to alpha or graphics, whichever is being
updated at the moment.

The system measures the phase detector output in frequency segments, beginning
with the highest offset to be measured. Both data and spurs are normalized, cor­rected and graphed while each segment is being swept by the spectrum analyzers.
After the phase noise measurement has been completed, the PROCESS DATA
menu allows the user to obtain a hardcopy output, do re-plots, save the data ob­tained, or return to the MAIN MENU to start a new measurement. See the pre­vious PROCESS DATA MENU discussion on page 25 for a full explanation of
the softkey options.

38

CHAPTER

VEASY-^ Softkey Listing

ABORT Terminates the current process and brings the program back to the current menu.

ABORT LOADING Skips the loading of the missing SUB drivers into memory.

ABORT TEST Terminates the current measurement and brings the program back to the main

menu.

CAL NOISE BW Calibrates the resolution bandwidth of the HP 8566/68 A/B Spectrum Analyzer.

CHANGE PARM Used to modify the desired measurement parameter indicated by the cursor ==>.

CONNECTED Press this softkey when the connection instructed by the software have been made.

COUNT I.F. SIG Updates the carrier frequency of the DUT according to the measured value of the

I.F.

signal frequency and the approximate value of the DEVICE FREQUENCY

parameter menu entry.

COUNT iiW SIG Directly counts the carrier frequency of the DUT on the Spectrum Analyzer and

updates its value.

CRT~>PRINTER Dumps the CRT graphics and alpha display to the HP-IB graphics printer

connected to the system.

DC FM Select this phase locking technique when measuring stable free-running sources

using the Phase Detector Method.

DFILE CATALOG Gives a catalog of the four possible EASY_,i?data files stored on the currently

specified data file disk.

DFILE DISK? Used to specify the disk drive that contains the disk from which data is to be

recalled or to which data is to be stored.

DISCR: I.F. CAL Select this option if you are making a phase noise measurement using the

Frequency Discriminator Method and the HP 8662A/63A is part of the system.
Also,

select this option if you are using any other RF source to calibrate the delay

line/mixer discriminator.

DISCR: /iW CAL Select this option if you are using a microwave source or the microwave DUT to

calibrate the delay line/mixer discriminator.

DISCRIMINATOR The discriminator method is used when measuring phase noise on unstable free-

running sources. The software will give the user instructions on how to connect

the system for a frequency discriminator measurement.

EFC Select this phase locking technique when measuring a stable synthesized source

using the Phase Detector Method.

EXIT Leaves the current menu and displays the next higher menu on the screen.

EXTERNAL PLOTS Allows the user to plot the measurement results on the CRT and/or to an external

plotter.

39

UP

Press this softkey after you are done setting up your microwave source as the cali­bration source in the Frequency Discriminator Method.

GOT QUAD

INSTALLED

LOAD MAIN PGM

LOAD SUBS

MAIN MENU

MANUAL LO

MANUAL LOCK

Press this softkey when quadrature is obtained (this softkey is shown when doing
a frequency discriminator measurement or locking manually in the Phase Detector
Method).

Press this softkey after installing the high-pass filter at the input of the HP 3561A.

Loads and runs the phase noise measurement program after the start-up message is
shown. Press after all instruments are connected and their respective HP-IB
addresses have been checked.

Starts loading the missing SUBS corresponding to the connected HP-IB
instruments.

Returns to the main menu.

Press this key when using a local oscillator that will not be automatically con­trolled. Remember to connect the 640 MHz signal needed to generate the series of
comb lines in the Phase Detector Method. Or, if using the Frequency Discrimina­tor Method, use the cable-attenuator assembly provided with the HP 11729C to
configure this instrument for stand-alone mode.

Choose manual lock when you are not familiar with the characteristics of the
source under test. Manual lock allows the user to directly observe and iterate the
loop bandwidth, and therefore quickly maximizes the range of valid measurement
data.

MEASURE NOISE

NEXT

NO CHANGE

NO FILTERING

NONE OF THESE

PAUSE PROGRAM

PREVIOUS

PROCESS DATA

RECALL DATA

Starts the phase noise measurement using the currrent Main Menu parameters.

Displays on the screen the next page of the start-up message.

Leaves unchanged the parameter that the double arrow is pointing at.

Press this softkey if you choose not to install a high-pass filter to prevent the HP
3561A from autoranging.

Press this softkey if the instruments connected to the indicated HP-IB address, is
not one of the softkey choice model numbers.

Stops the phase noise measurement program. Press [CONTINUE! to get back to
the MAIN MENU.

Displays (on the screen) the previous page of the start-up message.

Used to save/recall the current data, do re-plots, graph more than one measure-

ment result on the same plot, etc. Allows access to the Process Data menu.

recalls measured data from a disk or from the computer memory (last measure
data) to the CRT.

40

RE-COUNT FREQ Press this softkey if you want the software to re-count the microwave carrier

frequency or the IF frequency during the IF or /nW signal count.

REDRAW PLOT Redraws on the CRT the last measured data stored in computer memory.

REDRAW AXIS Blanks the display and redraws on the CRT the graph axis according to the

current parameters.

RE-MEASURE Re-measures the noise using the last specified parameters and calibration. RE-

MEASURE key disappears on RUN, or when a non-graph parameter is changed
via the Main Menu.

REMOVED Press this softkey after you are done removing the high-pass filter from the input

oftheHP3561A.

RE-PLOT Redraws the last measured data that is currently in memory on the screen, using

the current graph parameters.

RE-START Returns the program to the first page of the start-up file.

SAVE DATA It is used to save the current measurement results to a mass storage.

SEE GRAPH Shows on the CRT the data stored on the current graphics memory of the

controller.

USE THIS COUNT Press this softkey if you want the software to update and use the value of the

microwave frequency to the new measured value.

VIEW AUTO When this key is pressed EASY_J§? automatically switches between the alpha

display and the graph display as each is updated.

VIEW GRAPHICS Displays on the screen the data that is being measured.

VIEW MENU Displays on the screen the measurement parameters and current measurement

operation.

41

CHA1TES

VI

Measurement Difficulties

Measured Data Appears in Error at
Low Offset Frequencies

Figure

21.

Phase noise suppression inside

the loop bandwidth.

This section explains some of the measurement subtleties that the user may
encounter when making a measurement with EASY^j^ For each measurement
difficulty a probable cause and a corresponding corrective action are given to help
overcome the problem.

Cause: Suppression of phase noise at the output of the phase detector for offset
frequencies less than the bandwidth of the PLL. See Figure 21.

Correction: Try to minimize the PLL BW while still maintaining quadrature.
Software enhancements are needed to provide for corrected data inside the loop
bandwidth.

(BW NORMALIZED) * NOMINAL LOOP BW-1 kHz

0

■H> -40

N

o

DO

ao

T

"

—-120

-160
100 IK 100k 1M 1DM

*

/

/

I

(

1

(GRID LINES IN SEQUENCE OF 1, 2, 4, 6, 8)

OFFSET FREQUENCY Hz

Beat Note Not Found

System Cannot Phase Lock to
the Signal

Cause: Source not connected, not oscillating, or insufficient amplitude.
Correction: Check source connections and characteristics. Also check the para-

meters list for erroneous frequency entry (specifically, check DUT frequency
against actual DUT frequency by doing an IF COUNT or a UW SIGNAL
COUNT).

Cause: Excessive frequency drift, tuning voltage not effective, or loop bandwidth
chosen too small.

Correction: Check that the tuning line is connected and tuning capability of

source is activated. Try locking manually. Increase the Loop Bandwidth to accom­modate the expected source drift during the measurement. Try to isolate micro­phonics from DUT and from the system. Isolate line spurs using a line stabilizer.

Out of Lock Indicator Tripped Cause: Sources have drifted apart more than 20% of the available tuning range.

Correction: Increase the phase lock loop bandwidth by increasing the Lock Band­width Factor or the Peak Deviation set on the front panel of the HP 8662A/63A
(if DC FM locking is employed).

Incorrect Spurious Signal Levels
Observed

Cause: The software does not differentiate spurious signals from noise and so
applies Bandwidth normalization correction to the discrete signals (spurious).
Therefore, the spurs are reduced from the full value by the bandwidth correction.
Also,

the effective measurement threshold is actually above the displayed noise

levels,

due to the bandwidth correction. Hence, a spur above the displayed noise

floor but below the bandwidth corrected level, will not be shown.

Correction: Software enhancements are necessary to obtain a correct spurious
signal level reading.

42

Figure 22. Effect of noise peaking on the

phase noise graph.

BW NORMALIZED) * NOMINAL LOOP BW-1 kHz

0

£ -40

o

CO

■D

| -BO

/*

w

*

5

j

'/

OFFSET FREQUENCY Hz

(GRID LINES IN SEQUENCE OF 1, 2, 4, 6, 8)

Noise Peaking

"-120

-160
100 Ik 10k 100k 1M 10M

Cause: The phase lock loop bandwidth selected is close to an effective internal
Low Pass Filter cut-off frequency (3 kHz if locking via EFC) which causes the
loop to be unstable. See Figure 22. For a test frequency of 10 GHz, the HP

11729 B/C 10k and 100k lock bandwidth factors always yield an unstable loop.
In some situations, the Ik lock bandwidth factor might also be unstable, and will
always give a loop amplitude response which peaks up several dB before rolling off.

Correction: Select a smaller lock bandwidth factor or choose to lock via DC FM
if a smaller factor does not yield a loop bandwidth large enough to lock up the
two sources.

Discontinuities in the Graph Cause: The presence of large spurious signals with levels that exceed the dynamic

range of the HP 3561 A, cause this spectrum analyzer to autorange. The autorang-

ing of the Dynamic Signal Analyzer attenuates the noise of the DUT below the
noise floor of the HP 3561 A. The noise that is measured in this case is the noise

floor of the spectrum analyzer, not that of the DUT. The discontinuities that

appear in the graph are due to this autoranging of the HP 3561 A.

Correction: The software will prompt you to connect a high-pass filter at the

input of the HP 3561A in order to filter out the line spurious that cause the
Dynamic Signal Analyzer to autorange. Remove the filter when measuring noise
at offsets less than the filter's loop bandwidth.

HP 11729 B/C Internal
Misinterpretation of
Quadrature Condition

Cause: An adjustment on the Phase Lock Board in the HP 11729C sets the lock
and unlock trip thresholds on the Phase Lock Indicator. If the Phase Lock Indi­cator does not agree with the status byte sent out over HP-IB, the Phase Lock
Board may need adjustment.

Correction: Perform the Phase Lock Indicator adjustment. Follow the standard
procedure outlined in Section 5-7 of the HP 11729C Operating and Service

Manual.

43

A Easy_^ Main Program Variables Definitions

MAIN PROGRAM ONLY

Abort

Auto__scale

Avg_no

Avg_way (R) Tells where sweep averages are computed during Measure Noise.

Baseband_filt

Bbeat(*)

* (I) A flag used to exit lower level subroutines. A non-zero value in those routines

which use 'Abort' causes that routine to end without completing it's designed task.

(I) =0 if plot limits shouldn't be automatically chosen. =1 if plot is to be automat-

ically scaled based on data. (Default = 1, autoscale.)

(R) =1, 2, 4, 8,16, or 32; number of sweeps to be averaged on SA.

(Default = 1 sweep)

Avg-jno averages and returns one averaged trace to controller;
back each sweep of SA and averages internally. (Controller averaging is rather
slow.)

(R) A high-pass filter can be used to suppress low level spurs while an FFT analyzer

measures higher-band noise data. This variable equals the baseband filter frequency
in Hertz. Zero means the high-pass filter isn't currently being used. The program
actually prompts the user to put the filter in whenever any noise >= 10*
Baseband_filt is measured on the FFT analyzer (i.e., HP 3561A).

(R) One row element per measurement band. When the frequency band corresponding

to that element is measured for noise on SA's, the system will be beat-note
calibrated (or discrete-spur calibrated for delay line).

1—Controller

0—-SA

does

reads

Bcor(*) (R) Holds band correction factors for the currently selected measurement method.

Phase Detector: Col. 1: 2.5 dB plus Resolution BW of SA (in dB)

Col. 2: —6 dB for double-sideband^single-sideband Script L

Col. 3: -40 dB Calib. atten. step

Col. 4: =Calibration power measured in SignaLxal

Delay Line Dis: Col. 1: (Same as Col. 1 for PDetect Method)

Col. 2, 3: Not used and set to zero.

Bfreq(*)

Bnav(*)

Bno(*)

Bptr(*)

Col. 4: (dBc of

(R) Each measurement band measured data spans the offset frequency range in

Bfreq(*,l) through Bfreq(*,2). This is the data's frequency range, NOT the SA

span. SA span is dynamically increased to force the datapoints to agree with

Bfreq's range at each band.

(R) Number of

averaged.

(R) Indicates the sequential order which the bands are going to be measured. Bno(l)

equals number of total bands; as the row count increases, the Bno(*) decreases by

1 till last band, whose Bno(*) row element is 1. Hence, the bands corresponding to
the higher frequency band numbers are measured first.

(R) The pair of numbers at each row entry point to where in the SA measurement

array Noise(*) the data is for that band. For example, Bptr(3,l)=300 and
Bptr(3,2)=399, then the SA measured data corresponding to the band of row
3 in COM/Btbl/ is between Noise(300) and Noise(399) inclusive.

SA

sweeps taken in each band. Avg_way tells where those sweeps are

cal.

spur) — (discr. spur ampl.)

(I) = Integer, (R) = Real

44

Brbw(*) (R) Resolution BW that the SA is set to before or during the Measure of noise for each

band. Analog SA's get set to this BW, and DFT (i.e., HP 3561 A) report back their
resolution BW to this array after their spans have been set per Bfreq(*).

Bsa(*) (R) Tells which SA is to be used at each band. The value is used as a pointer into the

COMmon /Sa_tbl/ structure's row elements.

Bvbw(*) (R) The video BW used on an analog SA at each band. For digital DFT SA's, the

corresponding row element in Bvbw(*) is

—1

and completely unused.

Changed_val (I) Used in test parameter change subroutines in MAIN to flag when the variable

chosen for modification is actually changed.

Choice (I) When calls are made to the Key_sel softkey selection program, this variable is

used to return the softkey number chosen by operator.

Clock_mask (I) When non-zero, this variable disables the clock updating on row 1 of the CRT.

Used during Gbw cal of

SA,

cataloging of datafile disk, etc.

Cns_tbl(*) (R) Holds attributes of the currently used carrier noise test set. Since there's only one

CNS in the system, only row one is used. Col l=CNS's HP-IB address; all other
columns equal 0.

Discr_cal_type (I) Tells if the delay line discriminator is calibrated with an IF frequency source (=0)

or a fiW source (=1). The IF calibration source will be the automatically tuned
HP 8662A/63A if it has been configured per program's driver loading instructions
when the program is

first

run. A manual source is also possible at IF. The /uW cal

source must be manually controlled and tuned to the /JW DUT'S frequency.
Note: The frequency deviation and rate of the calibration sideband for the delay

line method is specified in the Discr_£al subprogram. They are assigned into local

variables Fsband and Dsband just after line Discr^caLmid in the EASY-££ file.

Err (I) Returns back from Subs with an error number that's dependent on the called

program segment.

Fc (R) Returns back from Filter_band subprogram call with the comb frequency that

corresponds to the

Fcor(*) (R) Delay Line method only; used to compute —20*LGT(F

F

frequency that was passed in.

dut

offset/Fdut

) where

F

offset

determined by each band's frequency in Bfreq(*). This applies a slope correction
to the discriminated spectrum which, when added column by column to the
corrected Noise(*) elements, yields Script-L.

Fdut (R) Equals frequency of device under test (DUT). Initially measured by /uW_signal

and ILsignal routines, and used by Measure Noise to acquire lock. (Default =10

GHz).

Units Hz.

Fif (R) Returns from Filter_band call with the IF corresponding to the

F

which had

dut

been passed in.

Fm_max (R) (100 Hz to 200 KHz) FM sensitivity on 866x generator, as inputted by user.

Units Hz. (Default = 200 kHz).

is

Fstart (R) =100, 300, Ik, 3k,.. 3 MHz. Starting offset frequency where noise is to be

measured. (Default = 1 kHz) Units Hz.

45

Fstop

(R) 300, Ik, 3k,..,10 MHz. Stopping offset frequency where noise is to be measured.

(Default = 1 MHz) Units Hz.

Ft

(R) Returns from Filter_band call with the HP 11729C filter number needed to down-

convert the

F

freq which was passed into Filter_band.

dut

Gbwf(10) (R) =GAIN-BW factors measured in Cal_bw routine. Indices are for HP 8666/68 SA

resolution BW:

Glast

1 - 10 Hz
2 - 30 Hz
3 - 100 Hz
4 - 300 Hz

(R) Shows the last actually set state of the alpha/graphic display. =1 — GRAPHICS

5 - 1 kHz
6 - 3 kHz
7-10 kHz
8-30 kHz

9 - 100 kHz

10 - 300 kHz

was last on, =0 — ALPHA. This differs from Gmode in that it tracks the actual
set mode of the CRT, instead of what the program would set it to if it WASN'T
LOCKED. Thus, if Glock=l and Crt_alpha or CrLgraph were called, Glast
would not changed because all CRT display changes are locked out. Gmode
would, however. Part of COM /Gmode/.

Glock

(R) When =

1,

the Crt_graph and Crt_alpha CALLs are ignored, and the CRT remains
in the graph/alpha mode determined by Gmode. (The Crt_alpha and Crt_graph
calls are kept track of within COMmon /Gmode/ , but they aren't used to change
the CRT mode.)

Gmode

1—Graphics

mode; 0—Text mode for CRT display mode. These

(R)

modes are changed by calls to Crt_graph and Crt_alpha. If the
Glock is set <>0, then Gmode is updated with calls to CrLgraph
and Crt_alpha—but no change is made to Glast or the CRT mode.

Hpib_gone

Lbwf

Lo_tbl(*)

Lost-Jock

Max_ptr

Method

(I) Part of COM /Main/, this is set <>0 when the program couldn't find an HP

8566/68 A/B, or an HP 11729A/B. This is done in the HpibJnit subroutine in
MAIN program. All main menu choices are blocked out <>0 except for the data
post processing key. This checking would have to be changed if the program were
modified to work with a different SA.

(I) =(1,2, 3, 4, 5); Lock Bandwidth Factor for HP 11729B Test Set. Corresponds to

the HP 11729C front panel legend via

10**(Lbwf—

1).

Default =

3,

corresponding

to front panel LBWF of 100.

(R) Holds local oscillator's (LO) characteristics. Since only one LO is allowed at a

time,

Lo_tbl(*) has only 1 row. The columns are: 1 - HP-IB Address; 2 - unused;

3 -

F

of LO (Hz), 4 -

min

F

of LO (Hz); 5 - Length of fast learn string. These

max

values are looked up by calling Lo-xapab-jq.

(I) Set by Srq_server subprogram during a noise measurement if

it

both gets jumped to
because of SRQ (during Measure subprogram execution) and the HP 11729 CNS
was out of lock.

(I) Returned by Menu_init, equals number of rows displayed in current menu.

(I) =(1 or 2) Phase Lock Method to be used with HP 8662 A/63 A; 1 = Elect. Freq.

Ctl;

2 = DC (866x Front Panel) FM. (Default = 2, lock by DC FM). Unitless.

46

Noise(*)

(R) Holds uncorrected noise data. To be changed into one array each for frequency,

noise, and spur measured.

Noise_hi

NoiseJo

Not_fhere

Pflag

Pointer

Pvector(50,2)

(R) 1

During measure, this keeps track of the largest plotted script-L dBc value. It's used
1

by the autoranging function to determine Y-axis limits automatically.

(R) 1

During measure, this keeps track of the LOWEST plotted script-L dBc value. It's

i

used by the autoranging function to determine Y-Axis limits automatically.

Used during Hpib_init subroutine (main program) in calls to the CnsJd, Sa_id,

(I) '

and Lo_id subroutines to see if a physical device is actually connected to the bus.

A "dirty" flag; indicates when a value (other than date and time) in menu has been

(R)

changed and should be updated to disc the next time a Cal BW, Analyze /uW,
Analyze IF, or Measure Noise is called. = 1 means diskfile should be updated; =0

-»no update needed.

(R) Indicates current position of the screen cursor, and is used to tell which row of

menu item is currently being worked on. Pointer also equals the row number on
CRT where cursor is, as well as the current Pvector(*) row number.

(I) Row 1 = a parameter assignment number. Row 1 breaks down as follows; values

found in this row mean the following:

1_F

dut

2 " Fstart

3 - F

J r

stop

4 - Video Smoothing

5 - # Sweeps to Average
6 - EFC Method used
7 - Lock BW Factor

9 - RESET all parameters to DEFAULT
10 - Date (Pvector(*,2)=0)
ll-Time(Pvector(*,2)=0)
12 - FM Deviation for 866x
13 - Plot scaling

14 - Top plot scale
15 - Bottom plot scale

8 - Spectrum Analyzer=HP 8566/68? 16 - Optional label for plot

Recal

Rev

Revx

Sa_no

(I) Determines whether or not the MeasureJioise SUBpgm should do a new discrim-

inator calibration (or beat-note cal) before noise gets measured. O^do not recal;

1—calibrate

normally. If any test parameter EXCEPT FOR Y-Axis scaling or the
Data Label gets changed, Recal gets set back to one to indicate a REMEASURE
option is not available for the next noise measurement

sequence.

If

Recal

is 0, and a

previous run has been taken, the main menu show a REMEASURE NOISE option

just below the MEASURE NOISE key; that button allows the noise measurement

to use the last calibration. If Recal=l, that function is not shown.

(R) Containing the current revision code of the program. This revision number gets

printed at the upper right corner of the main menu.

(R) =Revision number of program which recorded on the last default parameter file

from which the program had first loaded. It is updated whenever the main program
reads the default parameter file.

(R) Identifies the currently active SA. This is set by calling Sa_jchoose, or Sa_select,

which assigns the @Sa I/O path to one of the two SA's, and sets Sa_no to point
to the row in the COMmon /Sa_tbl/ arrays for that spectrum analyzer.

47

MAIN PROGRAM STRINGS

Atof$[l] =CHR$(128); turns CRT attributes off when printed.

Bl$[l] =CHR$(130); turns on CRT blinking attribute.

Clear$[21] =CHR$(255) and CHR$(72); simulates CLEAR-SCREEN keystroke when

Cns_files$(*) One-row array whose columns are: 1 - the HP 11729's response to instrument ID

D$[80] Used to form and pass DISPlay messages to SUBs.

Date$[18] The date is placed here in BASIC'S TIMEDATE format.

Df_-disk$[160] The disk's mass storage unit specifier for where the program looks to SAVE and

Df_plot$[160] Plotter specification where external plotting is sent—when so selected via the

File$[10] ="ELparams," the diskfile where the parameters are kept.

output to the keyboard (SHIFT-CLEAR LINE).

(Example: "11729C"); 2 - Filename of where the carrier noise test set is (example:
"ELI

1729X").

RECALL measured noise data files.

EXTERNAL PLOTS softkey in the See_data menu.

This array is set up based on the Cns_id Subprogram.

Fpref$[2] The two characters the program appends to the beginning of any filename during

any file operation. If you don't like the EL at the beginning of all the
the assign statement in the Mainvar_init subroutine, and change all the filenames
on the disks. (Nearly all calls use FprefS.)

Gd$[80] Holds the current alpha DISPlay value in COMmon /Gmode/ block. This is set

and cleared via calls to Crt_alpha w/Gd$ passsed in.

Home$[2] =CHR$(255) and CHR$(84); simulates SHIFT-DOWNARROW when output

to the keyboard; it homes the screen vertically.

Ivon$[l] =CHR$(129); turns on CRT Inverse Video attribute.

Klabel$(10)[16] A Null-set of key definitions which are passed to Key_sel when the main menu is

being shown. The dummy parameter is needed to allow the specification of
pointer variables for the cursor.

Label$[60] =User defined label that goes on top of

Lo-files$(*) A one row array containing information about the current LO (local oscillator).

Column: 1 - Current LO's response to an instrument ID (actually determined by
the length of it's fast learn string); column 2 - Filename of driver for current LO.
This array is set up in the Lo_id subprogram.

plot.

(Default = "")

files,

change

Menu$(15)[80] The last 'MenuJnit'-ed menu. This array is assigned when the Menu_init subpro-

gram is called to reflect the current values of all test parameters.

Sa_files$(*) Two rows each holding info on the identity of the two configured SA's. The

columns are: 1 - SA's response to instrument ID. 2 - The name of the driver file
for that SA. (Examples: "8566A" and "EL856XX.")

48

Sold$[80] Holds old string values for the date and label test parameter modification subrou-

tines (Set-date and Enter-label).

Subs Jisk$[160] Disk Mass Storage Unit Specifier where the SUBPGMS will be loaded from dur-

ing configuration. This includes the driver kernel "ELdrKERNAL," as well as
instrument drivers. The pgm loads the drivers it needs at run time based on what

instruments are on and identifiable.

Time$[18] =the time in the format required for the SET TIME statement in BASIC.

Ul$[18] =CHR$(132); causes CRT Underlining attribute to be turned on when printed to

the CRT.

Sa_tbl(*) (R) Holds characteristics for both SA's (two rows in table). The columns are:

1 - HP-IB Address; 2 - #pts/trace; 3 - Low frequency range of SA; 4 - High-end
frequency range of SA; 5 - 1 if an analog SA with programmable BW; 0 if a
Digital Four. Xform SA like the HP 3561A. This is assigned in the Sa^capab^q
SUBprogram.

SeLcode (I) Used in the STATUS query to look up the SA's (and assumably the other instru-

ment's) HP-IB select code. This is usually 7.

Spur(*) (R) NOT CURRENTLY IMPLEMENTED. We thought about saving peak values of

noise in this array, and plot discrete line spectra without the BW correction. One
might also write a spur seek routine to look away from the carrier for spurs with
the SA resolution BW at its narrowest span. Size of this has been reduced to 1
since it isn't being used.

Sweep^completed (I) Used in Measure_noise and Srq_server SUBs, this flag is set Srq_server when

an srq is received during a measurement and the resulting SA serial poll indicates
the SA has finished with its sweep. Measure_noise clears this flag before the
measurement is started and srqs get enabled.

Temp (R) Holds test parameters while their values are being shown to the user for change.

Used only in MAIN.

Timedate (R) Used to save and recall the time and day from the Series 200 internal clock as part

of the Set_jdate and Set-time subroutine, and while reading the time/date in off

disc file ELparams.

User_max (R) User-specified top of scale on plot. Units are dBc; (Default = —50 dBc).

User_min (R) User-specified bottom of scale on plot. Units are dBc. (Default = —150 dBc).

Userioprog_gone (I) Used to see if the Default parameter file is located on mass storage unit subaddress

0. If not, it assumes the file is located on subaddress 1. (Subaddresses refer to

mass storage units such as dual disc drives.)

Video_bw (R) Video bandwidth smoothing factor. This is NOT the actual video BW sent to the

SA. (Actual SA video bandwidth is a function of the resolution bandwidth; SA
VidBW=ResBW/VideoJbw.) (Default = 3). Unitless.

Void (R) Holds the unchanged value of a test parameter while that parameter is being

prompted to the user for change.

Voldl (R) Same as Void above. Some subroutines have two variables they could change, and

this tracks the second variable.

49

D

Easy-^gf Phase Noise Measurement Program

Subprogram
and

Sizes

EASY_^

Main Program

Tests

Test Utilities

Parameter Handlers RecorcLparams

Locations

Name

MAIN

Uw_signal
IfLsignal
Measure_noise
Cal_noise_bw
Discr_cal

Srq_server

SignaLseek
SignaLlock
Read_instr_parm
Signal_beat_cal
Sig_lost_prompt
Btbl_create_sub
FNFreq_stop
Quad_tone
Quad_check

Filter_band
FNMeasure_done
FNLoop_bw
FNCap_bw

Noise_to_ary

Data_save

Dfile_save
Dfile_cat
FNDfiIe_name$
Dfile_warn
Dfile_get_head
Data_recall
Dfile_recall
Dfile_plot_sel
Plotter_is
F_bdat_open

F_bdat_create
FNF_error$
D_init
D_select
FNMsu_base_name$
FNFile_spec$
Subpgm_load
Pgm_pause

Bytes

34264

7122
7718

25922

9734

18338

2424
14140
12342

3090
3196
2502

13016

1458

592
950

1358
1654

712
1402
1488

2554
3298
4098
6012

884

802

1080

6244

2982
3458
4648

690
1058
1914

2078
3614

1738

956
1342
1086

ELuserlO

User

I/O

Subprograms

CRT

Mode Selection

Graph Plotting Package

"Hidden"

Diagnostics

Name

Menu_init

FNMenu_insert$

Menu_print

Clock_update
Clear_message
Screen_clear
Screen_home_lft
FNFmt$
FNLoop_bw$
In
Key_sel
Key_init
Wait

Crt_alpha
Crt_graph
Crt_update
Crt_alpha_lk
Crt_graph_lk
Crt_unlock

Graph_init
Graph_dataplot
Graph_bandplot
Graph_lbwlabel
Graph_usrlabel

Graph_dfileplot

Graph_clear

Graph_lbwline
Log_plot
FNX_pos
Nice_scale
Move_for_label
LabeLlimits
Lin_plot
Vert_plot

BtbLprint
Mat_print

Bytes

9382

932
1070
1228
1126

408

434

2236

880
3042
8630

11644

988

2472

890
1092

770

750

772

5994

1826

4530

1850
1726

3284

958
4258
3024

502
2042

460

650

1268
1930

2370
2872

50

ELdrKERNAL

Name

Bytes

ELsaSTUBa Name

Bytes

Driver Support Routines

HP-IB Device

Virtual Frequency Counter

ID

Routines

EL11729X

11729 (CNS)

Driver

EL866XA

8662/3

(LO)

Driver

Kernal_there_q
Sa_choose
Sa_select
Driver_checker
Driver_loader

Cns_id
Lo_id

Sa_id

FNHpib_out_ent$

FNFreq_count

Cns_begin
FNCns_driver_q$
FNCns_fflter_q
FNCns_lbwf_q
FNCns_lost_lk_q
FNCns_locked_q
FNCns_id_q$
FNCns_lostlk_q
Cns_capab_q
Cns_unlock_e
Cns_srq_d
Cns_filter
Cns_lbwf
Cns_capture
Cns_mode
Cns_preset
A11729b_learn_q
Cns_end

Lo_begin
FNLo_driver_q$
FNLo_freq_q
FNLo_dcfm_q
FNLo_resolution_q
Lo_capab_q
Lo_freq
Lo_dcfm
Lo_fmdev
Lo_fmint
FNLo_dcfm_cap
Lo_preset
Lo_ampl
Lo_deltaf
Lo_deltaa
A866xa_learn_q

A8662a_range
A8663a_range
Lo_end

694

10630

828
5762
5584

3244
4320
3102
1250

5414

2434

284

520

516

340

302

446

900

1164

302

374

322

314

664

656

242

350

284

3416

474

1888
2412

720

1128

722
414

2570

718
990
266
512
540
442
478

900

432
282

Generic

(SA)

EL856XX

8566/68

A/B (SA)

Driver Sa_begin

FNSa_driver_q$
FNSa_sweep_q
FNSa_fpeak_q
Sa_marker_q
FNSa_rbw_q
FNSa_zoom_q
Sa_trace_q
Sa_capab_q
Sa_sweepend_e
Sa_srq_d
Sa_preset
Sa_span
Sa_rbw
Sa_vbw
Sa_local
Sa_remote
Sa_ref_lev
Sa_take_sweep
Sa_sweep_start

Sa_mrk_to_ref
Sa_mrk_to_fr
Sa_end

Driver Sa856xx_begin

FNSa856xx_driv_q$

FNSa856xx_sweep_q
FNSa856xx_fpeak_q
Sa856xx_mrk_q
FNSa856xx_rbw_q
FNSa856xx_zoom_q
Sa856xx_trace_q
Sa856xx_capab_q
Sa856xx_eos_e
Sa856xx_srq_d
Sa856xx_preset
Sa856xx_span
Sa856xx_rbw

Sa856xx_vbw
Sa856xx_local
Sa856xx_remote
Sa856xx_refLlev
Sa856xx_tk_swp
Sa856xx_swp_st
Sa856xx_mk_t_rf
Sa856xx_mk_t_fr
Sa856xx_end

2020

842
818
982
842
804

838
1236
1096

794

770
1220

834

786

790

804

802

838

990

982

822

836

282

4316

440

760

788

426

544

714

360

1304

286

422

1260

298
258
266
336
460
380

1106

774
286
316

198

51

EL3561A

Name

Bytes ELLOsource

Name Bytes

3561A

(SA)

Driver

Sa3561a_begin
FNSa3561a_driv_q$
FNSa3

561

a_sweep_q
FNSa3561a_fpeak_q
Sa3561a_mrk_q
FNSa3561a_rbw_q
FNSa3561a_zoom_q
Sa3561a_trace_q
Sa3561a_capab_q
Sa3561a_eos_e
Sa3561a_srq_d
Sa3561a_preset
Sa3561a_span
Sa3561a_rbw

Sa3561a_vbw
Sa3561a_local
Sa3561a_remote

Sa3561a_refLlev
Sa3561a_tk_swp

Sa3561a_swp_st

Sa3561a_mk_t_rf

Sa3561a_mk_t_fr

Sa3561a_ascii_q

FNSa3561a_r£_lv_q

FNSa3561a_fstop_q

FNSa3561a_fr_dec

Sa3561a_end

5064

446
876
842
442
660
816

1876

1134

406
376
534
408
476

652
340

364

390
1096
1172

904

314

758

604

786

804

198

ELkeys300

ELautost

Lo_begin
FNLo_driver_q$
FNLo_fireq_q
FNLo_dcfm_q
FNLo_resolution_q
Lo_capab_q
Lo_freq
Lo_dcfm
Lo_fmdev
Lo_fmint
FNLo_dcfm_cap
Lo_preset
Lo_ampl
Lo_deltaf
Lo_deltaa
Lo_end

Key_init

MAIN

3184
Message_load 2094
FNMsu_base_name$
FNFile_spec$

1026

3186

388
364
912
478

1108

542
466

936
854

546
568
458

542

582

186

11818

1858

52

Easy_Jj?f Ordering Information

Part Number 11729-60126 EASY_^software.

HP 11729C-3 Product Note,
"A User's Guide to Automatic Phase Noise Measurements"

Part Number 11729-60127 EASY_jg?software. (3W media)

HP 11729C-3 Product Note,
"A User's Guide to Automatic Phase Noise Measurements"

Note:

Additional copies of

Order HP literature number: 5954-6385.

(5V4*

media)

this

product note will be available at no cost.

53

■

5954-6385

HEWLETT

W1KM PACKARD

January 1986
Printed in U.S.A.