Agilent Technologies U2761A User Manual

Agilent U2761A
USB Modular
Function/Arbitrary
Waveform Generator

User’s Guide

Agilent Technologies

Notices

© Agilent Technologies, Inc., 2008

No p art o f this manu al may be reprod uced in
any form or by any means (including elec­tronic storage and retrieval or translation
into a foreign language) without prior agree­ment and written consent from Agilent
Technologies, Inc. as governed by United
States and international copyright laws.

Manual Part Number

U2761-90000

Edition

First Edition, April 30, 2008

Agilent Technologies, Inc.
3501 Stevens Creek Blvd.
Santa Clara, CA 95052 USA

Trademark Acknowledgements

Pentium is a U.S. registered trademark of
Intel Corporation.

Microsoft, Visual Studio, Windows, and MS
Windows are trademarks of Microsoft Cor­poration in the United States and/or other
countries.

Warranty

The material contained in this docu­ment is provided “as is,” and is sub­ject to being changed, without notice,
in future editions. Further, to t he max­imum extent permitted by applicable
law, Agilent disclaims all warranties,
either express or implied, with regard
to this manual and any information
contained herein, including but not
limited to the implied warranties of
merchantability and fitness for a par­ticular purpose. Agilent shall not be
liable for errors or for incidental or
consequential damages in connec­tion with the furnishing, use, or per­formance of this document or of any
information contained herein. Should
Agilent and the user have a separate
written agreement with warranty
terms covering the material in this
document that conflict with these
terms, the warranty terms in the sep­arate agreement shall control.

Technology Licenses

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

Restricted Rights Legend

U.S. Government Restricted Rights. Soft­ware and technical data rights granted to
the federal government include only those
rights customarily provided to end user cus­tomers. Agilent provides this customary
commercial license in Software and techni­cal data pursuant to FAR 12.211 (Technical
Data) and 12.212 (Computer Software) and,
for the Department of Defense, DFARS

252.227-7015 (Technical Data - Commercial
Items) and DFARS 227.7202-3 (Rights in
Commercial Computer Software or Com­puter Software Documentation).

Safety Notices

CAUTION

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

WARNING

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

II U2761A User’s Guide

Safety Symbols

Direct current (DC) Equipment protected throughout by

Alternating current (AC) Off (supply)

Both direct and alternating current On (supply)

Three-phase alternating current Caution, risk of electric shock

Earth (ground) terminal Caution, risk of danger (refer to this

The following symbols on the instrument and in the documentation
indicate precautions which must be taken to maintain safe operation of
the instrument.

double insulation or reinforced
insulation

manual for specific Warning or Caution
information)

Protective conductor terminal Caution, hot surface

Frame or chassis terminal Out position of a bi-stable push control

Equipotentiality In position of a bi-stable push control

U2761A User’s Guide III

General Safety Information

WARNING

CAUTION

The following general safety precautions must be observed during all
phases of operation of this instrument. Failure to comply with these
precautions or with specific warnings elsewhere in this manual violates
safety standards of design, manufacture and intended use of the
instrument. Agilent Technologies Inc. assumes no liability for the
customer’s failure to comply with these requirements.

• Do not operate the product in an explosive atmosphere or in the
presence of flammable gases or fumes.

• Do not use the equipment if it does not operate properly. Have the
equipment inspected by qualified service personnel(s).

• Observe all markings on the instrument before connecting any wiring to

the instrument.

• Use the device with the cables provided.

• Repair or service that is not covered in this manual should only be

performed by qualified personnel(s).

IV U2761A User’s Guide

Environment Conditions

CAUTION

This instrument is designed for indoor use and in the area with low
condensation. The table below shows the general environmental
requirements for this instrument.

Environment conditions Requirements

Operating temperature 0 °C to 50 °C

Operating humidity 20 to 85% RH non-condensing

Storage temperature –20 °C to 70 °C

Storage humidity 5 to 90% RH non-condensing

The U2761A USB modular function/arbitrary waveform generator
complies with the following safety and EMC requirements.

• IEC 61010-1:2001/EN61010-1:2001 (2nd Edition)

• Canada: CAN/CSA-C22.2 No. 61010-1-04

• USA: ANSI/UL 61010-1:2004

• IEC 61326-2002/EN 61326:1997+A1:1998+A2:2001+A3:2003

• Canada: ICES-001:2004

• Australia/New Zealand: AS/NZS CISPR11:2004

U2761A User’s Guide V

Regulatory Markings

The CE mark is a registered trademark
of the European Community.This CE
mark shows that the product complies
with all the relevant European Legal
Directives.

ICES/NMB-001 indicates that this
ISM device complies with Canadian
ICES-001.
Cet appareil ISM est confomre a la
norme NMB-001 du Canada.

The CSA mark is a registered
trademark of the Canadian Standards
Association.

The C-tick mark is a registered
trademark of the Spectrum
Management Agency of Australia.
This signifies compliance with
the Australia EMC Framework
regulations under the terms of the
Radio Communication Act of 1992.

This instrument complies with the
WEEE Directive (2002/96/EC)
marking requirement. This affixed
product label indicates that you must
not discard this electrical/electronic
product in domestic household waste.

VI U2761A User’s Guide

Waste Electrical and Electronic Equipment (WEEE) Directive
2002/96/EC

This instrument complies with the WEEE Directive (2002/96/EC) marking
requirement. This affixed product label indicates that you must not discard
this electrical/electronic product in domestic household waste.

Product Category:

With reference to the equipment types in the WEEE directive Annex 1, this
instrument is classified as a “Monitoring and Control Instrument” product.

The affixed product label is shown as below:

Do not dispose in domestic household waste

To return this unwanted instrument, contact your nearest Agilent office, or
visit:

www.agilent.com/environment/product

for more information.

U2761A User’s Guide VII

Declaration of Conformity

DECLARATION OF CONFORMITY

According to EN ISO/IEC 17050-1:2004

Generic example

Manufacturer’s Name:

Agilent Technologies Microwave Products (M) Sdn. Bhd

Manufacturer’s Address:

Bayan Lepas Free Industrial Zone,
11900, Bayan Lepas, Penang, Malaysia

Declares under sole responsibility that the product as originally delivered

Product Name:

Agilent USB Modular Function Generator

Models Number:

U2761A

Product Options:

This declaration covers all options of the above product(s)

complies with the essential requirements of the following applicable European Directives, and
carries the CE marking accordingly:

Low Voltage Directive (2006/95/EC)
EMC Directive (2004/108/EC)

and conforms with the following product standards:

EMC

Standard

StandardStandard

Standard Limit

LimitLimit

Limit

IEC 61326:2002 / EN 61326:1997+A1:1998+A2:2001+A3:2003
CISPR 11:1990 / EN55011:1990 Class A Group 1
IEC 61000-4-2:1995 / EN 61000-4-2:1995 4 kV CD, 8 kV AD
IEC 61000-4-3:1995 / EN 61000-4-3:1996 3 V/m, 80-1000 MHz
IEC 61000-4-4:1995 / EN 61000-4-4:1995 0.5 kV signal lines, 1 kV power lines
IEC 61000-4-5:1995 / EN 61000-4-5:1995 0.5 kV line-line, 1 kV line-ground
IEC 61000-4-6:1996 / EN 61000-4-6:1996 3 V, 0.15-80 MHz
IEC 61000-4-11:1994 / EN 61000-4-11:1994 1 cycle / 100%

Canada: ICES-001:2004
Australia/New Zealand: AS/NZS CISPR11:2004

The product was tested in a typical configuration with Agilent Technologies test systems.

Safety

IEC 61010-1:2001 / EN 61010-1:2001
Canada: CAN/CSA-C22.2 No. 61010-1-04
USA: ANSI/UL 61010-1:2004

206349

This DoC applies to above-listed products placed on the EU market after:

08-Jan-2008

Date

Tay Eng Su

Quality Manager

For further information, please contact your local Agilent Technologies sales office, agent or distributor,

or Agilent Technologies Deutschland GmbH, Herrenberger Straße 130, 71034 Böblingen, Germany.

Template: A5971-5302-2, Rev. E U2761A DoC Revision 1.0

VIII U2761A User’s Guide

Product Regulations

Performance Criteria

IEC 61326-1:2002 / EN 61326-1:1997+A1:1998+A2:2001+A3:2003

CISPR 11:1990 / EN 55011:1990

– Group 1 Class A

IEC 61000-4-2:1995 / EN 61000-4-2:1995

(ESD 4kV CD, 8kV AD) A

IEC 61000-4-3:1995 / EN 61000-4-3:1996

(3V/m, 80% AM) A

IEC 61000-4-4:1995 / EN 61000-4-4:1995

(EFT 0.5kV line-line, 1kV line-earth) B

IEC 61000-4-5:1995 / EN 61000-4-5:1995

(Surge 0.5kV line-line, 1kV line-earth) A

IEC 61000-4-6:1996 / EN 61000-4-6:1996

(3V, 0.15~80 MHz, 80% AM, power line) A

IEC 61000-4-11:1994 / EN 61000-4-11:1994

(Dips 1 cycle, 100%) A
Canada: ICES-001:2004
Australia/New Zealand: AS/NZS CISPR11:2004

EMC

IEC 61010-1:2001 / EN 61010-1:2001

Canada: CAN/CSA-C22.2 No. 61010-1-04

USA: ANSI/UL 61010-1:2004

Safety

Additional Information:

The product herewith complies with the essential requirements of the Low Voltage Directive 2006/95/EC and the
EMC Directive 2004/108/EC and carries the CE Marking accordingly (European Union).

1

Performance Criteria:

A Pass - Normal ope ration, no effec t.
B Pass - Temporary degradation, self recoverable.
C Pass - Temporary degradation, operator intervention required.
D Fail - Not recoverable, component damage.
N/A – Not applicable

Notes:

Regulatory Information for Canada

ICES/NMB-001:2004
This ISM device complies with Canadian ICES-001.
Cet appareil ISM est confomre à la norme NMB-001 du Canada.

Regulatory Information for Australia/New Zealand

This ISM device complies with Australian/New Zealand AS/NZS CISPR11:2004

U2761A User’s Guide IX

In This Guide…

1 Getting Started

In this chapter, you prepare your system for installation and configuration
to get started with the U2761A.

2 Features and Functions

In this chapter, you will learn about the functions and features offered by
the U2761A.

3 Characteristics and Specifications

In this chapter, you will observe the product characteristics and
specifications.

X U2761A User’s Guide

Contents

List of Figures XV

List of Tables XVII

1 Getting Started 1

Introduction 2

Product at a Glance 3

Product Outlook 3

Product Dimensions 5

Dimensions Without Bumpers 5
Dimensions With Bumpers 6

Standard Purchase Items 7

Inspection and Maintenance 8

Initial Inspection 8
Electrical Check 8
General Maintenance 8

Installation and Configuration 9

Installation 9
A. Check Your System 10
B. Install the IO Libraries Suite 11
C. Install the Module Driver 12
D. Install the Agilent Measurement Manager 13
E. Connect the Module to Your PC 15
F. Verify Your Module Connection 19
G. Launch Your Agilent Measurement Manager 21
55-Pin Backplane Connector Pin Configuration 23
Chassis Installation 24

U2761A User's Guide XI

Contents

2 Features and Functions 25

Output Configuration 26

Introduction 26
Output Function 26
Output Frequency 29
Output Amplitude 31
Output Units 35
Output Termination 36
Duty Cycle (Square Waves) 38
Symmetry (Ramp Wave) 40
Output Control 41
Set Output Using SCPI Commands 42

Pulse Waveform 45

Pulse Period 45
Pulse Width 46
Pulse Duty Cycle 47
Generate Pulse Waveform Using SCPI Commands 48

Amplitude Modulation (AM) 49

To S e l ec t A M 49
Carrier Waveform 50
Carrier Frequency 51
Modulating Waveform 52
Modulating Waveform Frequency 53
Modulation Depth 53
Generate AM Using SCPI Commands 54

Frequency Modulation (FM) 55

To S e l ec t F M 55
Carrier Waveform 56
Carrier Frequency 57
Modulating Waveform 58

XII U2761A User's Guide

Modulating Waveform Frequency 59
Frequency Deviation 59
Generate FM Using SCPI Commands 60

Phase Modulation (PM) 61

To S e l ec t P M 61
Carrier Waveform 62
Carrier Frequency 63
Modulating Waveform 64
Modulating Waveform Frequency 64
Phase Deviation 65
Generate PM Using SCPI Commands 65

Frequency-Shift Keying (FSK) Modulation 66

To S e l ec t F S K M od ul at i on 66
Carrier Waveform 67
FSK Carrier Frequency 68
FSK “Hop” Frequency 69
Generate FSK Modulation Using SCPI Commands 70

Contents

Phase-Shift Keying (PSK) Modulation 71

To Select PSK Modulation 71
Carrier Waveform 72
PSK Carrier Frequency 73
PSK Rate 74
PSK Deviation 74
Generate PSK Modulation Using SCPI Commands 75

Amplitude-Shift Keying (ASK) Modulation 76

To Select ASK Modulation 76
Carrier Waveform 77
Carrier Frequency 78
ASK Rate 79
Generate ASK Modulation Using SCPI Commands 79

Frequency Sweep 80

U2761A User's Guide XIII

Contents

To Select Sweep 80
Start Frequency and Stop Frequency 81
Sweep Mode 82
Sweep Time 82
Sweep Trigger Source 83
Set Frequency Sweep Using SCPI Commands 84

Tri gg er in g 85

Trigger Source Choices 85
Internal Triggering 86
Manual Triggering 86
External Triggering 87
Trigger Input Signal 88
Trigger Output Signal 88
Set Triggering Using SCPI Commands 90

Arbitrary Waveforms 91

To Create and Store an Arbitrary Waveform 91

3 Characteristics and Specifications 95

Product Characteristics 96

Product Specifications and Characteristics 97

Index 103

XIV U2761A User's Guide

List of Figures

Figure 1-1 55-pin backplane connector pin configuration 23
Figure 2-1 U2761A soft front panel 28
Figure 2-2 Top panel view of the U2761A 29
Figure 2-3 Panel view of the frequency section 30
Figure 2-4 Panel view of the amplitude section 32
Figure 2-5 Panel view of the DC offset section 34
Figure 2-6 Panel view of the Tools menu 37
Figure 2-7 Square wave duty cycles 38
Figure 2-8 Panel view of the duty cycle section 39
Figure 2-9 Ramp wave duty cycles 40
Figure 2-10 Panel view of the symmetry section 40
Figure 2-11 Panel view of the output section 41
Figure 2-12 Pulse waveform 45
Figure 2-13 Panel view of the pulse width section 46
Figure 2-14 AM waveform 49
Figure 2-15 Panel view of AM 50
Figure 2-16 Panel view of the Arbitrary waveform 51
Figure 2-17 FM waveform 55
Figure 2-18 Panel view of FM 56
Figure 2-19 PM waveform 61
Figure 2-20 Panel view of PM 62
Figure 2-21 FSK modulation waveform 66
Figure 2-22 Panel view of FSK 67
Figure 2-23 PSK modulation waveform 71
Figure 2-24 Panel view of PSK 72
Figure 2-25 ASK modulation waveform 76
Figure 2-26 Panel view of ASK 77
Figure 2-27 Frequency sweep 80
Figure 2-28 Panel view of sweep 81
Figure 2-29 Trigger input pulse 88
Figure 2-30 Trigger output pulse 88
Figure 2-31 Ramp waveform 91

U2761A User’s Guide XV

XVI U2761A User’s Guide

List of Tables

Ta b l e 1 - 1 Synchronous Simultaneous Interface (SSI) connector

pin description 23

Ta b l e 2 - 1 Output functions 26
Ta b l e 2 - 2 Output frequency range 29
Ta b l e 2 - 3 Carrier frequency for AM 51
Ta b l e 2 - 4 Carrier frequency for FM 57
Ta b l e 2 - 5 Carrier frequency for PM 63
Ta b l e 2 - 6 Carrier frequency for FSK 68
Ta b l e 2 - 7 “Hop” frequency 69
Ta b l e 2 - 8 Carrier frequency for PSK 73
Ta b l e 2 - 9 Carrier frequency for ASK 78

U2761A User’s Guide XVII

XVIII U2761A User’s Guide

Agilent U2761A USB Modular Function Generator
User’s Guide

1 Getting Started

Introduction 2
Product at a Glance 3
Product Dimensions 5
Standard Purchase Items 7
Inspection and Maintenance 8
Installation and Configuration 9

This chapter provides the introduction of the U2761A that
helps you get acquainted with the product and the product
outlook. This chapter also includes the installation and
configuration procedures that will help you get started with
the U2761A.

1Agilent Technologies

1Getting Started

Introduction

The U2761A is a 20 MHz USB modular function generator
with Arbitrary waveform and pulse generation capabilities. It
can operate as a standalone or modular unit when used
with the U2781A USB modular instrument chassis.

The U2761A adopts the latest direct digital synthesis (DDS)
technology that digitally creates Arbitrary waveforms and
frequencies from a single, fixed source frequency. DDS offers
the precision of digitally control logic; reducing the
complexity of the generator while increasing the stability.
Thus, creating a stable, accurate output signal for clean, low
distortion sine waves with fast rise and fall time up to
20 MHz and linear Ramp waves up to 200 kHz.

Various features of the U2761A

• 20 MHz Sine and Square waveforms

• Hi-Speed 2.0, USBTMC 488.2 standards

• Sine, Square, Ramp, Triangle, Pulse, and DC waveforms

• 14-bit, 50 MSa/s, 64 K-point Arbitrary waveforms

• AM, FM, PM, ASK, FSK, and PSK modulation types

• 40 mVpp to 5 Vpp amplitude range for 50 Ω load, and

80 mVpp to 10 Vpp amplitude range for open circuit

• Pulse generation

2 U2761A User’s Guide

Product at a Glance

Bumpers

Product Outlook

Getting Started 1

Top V ie w

U2761A User’s Guide 3

1Getting Started

USB indicator

Power indicator

10 MHz reference connector

Trigger in connector

Trigger out connector

Output connector

Fan Ventilation

Power inlet

USB inlet

Fastening hole for USB cable with locking mechanism

55-pin backplane connector

Front View

Rear View

4 U2761A User’s Guide

Product Dimensions

Top V ie w

105.00 mm

175.00 mm

18.00 mm

Front View

25.00 mm

Dimensions Without Bumpers

Getting Started 1

U2761A User’s Guide 5

1Getting Started

Top V ie w

117.00 mm

180.00 mm

15.00 mm

Front View

41.00 mm

Dimensions With Bumpers

6 U2761A User’s Guide

Standard Purchase Items

Verify the following items for the standard purchase of the
U2761A. If there are any missing or mechanically damaged
items, contact the nearest Agilent Sales Office.

✔ 12 V, 2 A AC/DC power adapter

✔ Power cord

✔ USB Standard-A to Mini-B interface cable

✔ L-Mount kit (used with modular instrument chassis)

✔ Agilent Automation Ready-CD (contains the IO Libraries

Suite)

✔ Agilent USB Modular Products Quick Start Guide

✔ Agilent USB Modular Products Reference CD-ROM

✔ Agilent Measurement Manager Quick Reference Card

✔ Certificate of Calibration

Getting Started 1

U2761A User’s Guide 7

1Getting Started

NOTE

Inspection and Maintenance

Initial Inspection

When you receive your U2761A, inspect the unit for any
obvious damage such as broken terminals or cracks, dents,
and scratches on the casing that may occur during shipment.
If any damage is found, notify the nearest Agilent Sales
Office immediately. The front of this manual contains the
warranty information.

Keep the original packaging in case the U2761A has to be
returned to Agilent in the future. If you return the U2761A
for service, attach a tag identifying the owner and model
number. Also include a brief description of the problem.

Electrical Check

The U2761A USB Modular Function/Arbitrary Waveform
Generator Service Guide will provide the complete

verification and calibration procedures. The procedures will
verify to a high level of confidence that the U2761A is
operating in accordance with its specifications.

General Maintenance

Any repair that is not covered in your modular product manuals should
only be performed by qualified personnel.

1 Power off your module and remove the power cord and

I/O cable from your device.

2 Remove your module from the bumper casing.

3 Shake off any dirt that may have accumulated on the

module.

4 Wipe your module with a dry cloth and install the

bumper back in place.

8 U2761A User’s Guide

Installation and Configuration

NOTE

A. Check Your System

B. Install the IO Libraries Suite

C. Install the Module Driver

D. Install the Agilent Measurement Manager

E. Connect the Module to Your PC

F. Verify Your Module Connection

G. Launch Your Agilent Measurement Manager

Installation

Follow the step-by-step instructions shown in the following
flowchart to get started with the preparations and
installations of your U2761A.

Getting Started 1

You need to install the IVI-COM driver if you are going to use the U2761A
with Agilent VEE Pro, LabVIEW, or Microsoft

®

Visual Studio®.

U2761A User’s Guide 9

1Getting Started

A. Check Your System

Prior to any installation or configuration, please ensure that
your PC meets the following minimum system requirements.

Processor 1.6 GHz Pentium® IV or higher

Operating system Windows® XP Professional or Home Edition

(Service Pack 1 or later), or Windows® 2000 Professional
(Service Pack 4 or later)

Browser Microsoft® Internet Explorer 5.01 or higher

Available RAM 512 MB or higher recommended

Hard-disk space 1 GB

Video Super VGA 800×600 (1024×768 recommended)

Prerequisites Agilent IO Libraries Suite 14.2 or higher

(version 15.0
version 2.1

2

patch

, Microsoft® .NET Framework version 1.1 and 2.0

1 Available on Agilent Automation-Ready CD.

1

recommended), Agilent T&M Toolkit Runtime

2

, Agilent T&M Toolkit Redistributable Package 2.1

2

2 Bundled with Agilent Measurement Manager application software installer.

10 U2761A User’s Guide

B. Install the IO Libraries Suite

NOTE

NOTE

The IO Libraries Suite 14.2 or higher is available on the
Agilent Automation-Ready CD that comes with the standard
purchase of the U2761A.

• If you do not have the Agilent Automation-Ready CD, obtain the IO
Libraries Suite 14.2 or higher at http://www.agilent.com/find/iolib.

• Disconnect any USB instruments or connectivity interface from your
PC.

1 Close all other applications on your PC, insert the Agilent

Automation-Ready CD into your CD-ROM drive, and follow

the instructions on your screen.

2 If the IO Libraries Suite installation does not start

automatically, go to Start > Run (on the Windows Start
menu) and type <drive>:\autorun\auto.exe where

<drive>

3 If you obtain the IO Libraries Suite from the web, save

the self-extracting zip file (*.exe) to any location on your
hard disk.

4 Double-click the installation file to launch the installation.

5 Follow the instructions on your screen to proceed with

the installation.

6 After the installation has completed, you will see the IO

Control icon on the Windows taskbar notification area as
shown below.

is your CD-ROM drive location.

Getting Started 1

For detailed installation instructions, refer to the Agilent IO Libraries Suite
Getting Started Guide at http://www.agilent.com/find/iolib.

U2761A User’s Guide 11

1Getting Started

NOTE

C. Install the Module Driver

Please ensure that there are no instruments connected to the PC when
installing the driver.

1 Verify that your PC meets the minimum system

requirements as stated in “A. Check Your System” on
page 10.

2 Insert the Product Reference CD-ROM into your CD-ROM

drive.

3 The installer will automatically launch the Agilent Modular

Products Installation Menu. Click Hardware Driver to begin the

installation.

4 If the menu does not launch automatically, go to Start >

Run (on the Windows Start menu) and type <drive>:\

Driver\Hardware\setup_Hw.exe where <drive>
your CD-ROM drive location. Click OK to begin the
installation.

5 Follow the instructions on the screen and click Next to

proceed.

12 U2761A User’s Guide

is

6 Click Install to begin the installation. Follow the

instructions on the screen to proceed with the
installation.

7 Click Finish when the installation has completed.

D. Install the Agilent Measurement Manager

1 If you have done “C. Install the Module Driver” on

page 12, proceed to Step 2. If not, close all other
applications on your PC and insert the Product Reference
CD-ROM into your CD-ROM drive.

2 Click Measurement Manager on the U2761A Installation Menu to

begin the installation.

Getting Started 1

3 If the installation menu does not appear after a few

seconds, go to Start > Run and type <drive>:\
Application\Modular Instruments Measurement
Manager\setup.exe where <drive> is your CD-ROM

drive location.

4 Click OK to begin the installation.

5 If you do not have any of the prerequisites installed, the

InstallShield Wizard software prerequisite will appear.

U2761A User’s Guide 13

1Getting Started

NOTE

6 Click OK to begin the installation of the listed missing

prerequisites.

7 Once the above installation has completed, installation of

the Measurement Manager software will proceed as
normal.

8 The Measurement Manager InstallShield Wizard dialog will

appear. Click Next to begin.

9 Read the License Agreement and select I accept the terms in

the License Agreement to proceed. You may click Print to

print a hardcopy of the Agilent License Terms for
reference. Click Next to proceed.

10 Fill in the Customer Information Form accordingly and

click Next.

11 Click Next to install to the specified folder or click Change

to install to a different folder.

12 Click Install to begin the installation of the Measurement

Manager.

13 Click Finish when the installation has completed.

14 A shortcut to this software will be created on your

desktop.

USING THE LICENSED MATERIALS INDICATES YOUR ACCEPTANCE OF
THE LICENSE TERMS. IF YOU DO NOT AGREE TO ALL OF THESE TERMS,

using

YOU MAY RETURN ANY UNOPENED LICENSED MATERIAL FOR A FULL
REFUND. IF THE LICENSED MATERIALS ARE BUNDLED OR PRELOADED
WITH ANOTHER PRODUCT, YOU MAY RETURN THE ENTIRE UNUSED
PRODUCT FOR A FULL REFUND.

14 U2761A User’s Guide

E. Connect the Module to Your PC

NOTE

Ensure that the Agilent Measurement Manager is installed before
proceeding.

1 After the installations have completed, connect the power

cord to the AC/DC power adapter. The AC/DC power
adapter requirements are 100 to 240 VAC, 50/60 Hz, with
an output voltage of +12 VDC.

2 Insert the DC output plug from the AC/DC power adapter

to the power jack on the rear panel of the U2761A.

3 Connect the U2761A to any USB port on your PC with

the bundled USB cable.

4 Your PC will automatically detect the connected unit and

the Found New Hardware Wizard window will appear. Select

Yes, this time only and click Next to proceed.

Getting Started 1

U2761A User’s Guide 15

1Getting Started

5 Select Install the software automatically (Recommended) and

click Next.

6 A warning message will appear on the Hardware Installation

window. Click Continue Anyway to proceed with the
installation of the U2761A.

16 U2761A User’s Guide

Getting Started 1

NOTE

If you do not wish to receive similar warning messages in the future,
follow the instructions below.

• Go to Start > Control Panel and double-click System.

• Select the Hardware tab and click Driver Signing on the Drivers panel.
The Driver Signing Options dialog box will appear.

• Select Ignore to disable the warning message.

7 Click Finish to complete the installation.

U2761A User’s Guide 17

1Getting Started

8 The Assign USB device alias window will appear. Each time

the U2761A is plugged in, this dialog box will appear. To
disable this dialog, select the Never show this dialog option
in the Show this dialog panel and click

OK.

9 For modules other than the U2300A Series, U2500A

Series, U2600A Series, and U2781A, the system will
perform a firmware version check on your connected
module.

a If the module firmware version is the same as the

installed version on the PC, it will not perform any
firmware download and the U2761A is now ready for
use.

b If the module firmware version differs from the

installed version on the PC, the following message box
will appear. Firmware versions (V1.00 and V1.01) in the
figure are for illustration purpose only, it might vary
depending on the device and PC firmware version.

18 U2761A User’s Guide

Getting Started 1

NOTE

c Click Ye s to begin the firmware download. The

following message box will appear indicating the
download in progress.

Ensure that you do not remove the USB and power connection until the
firmware download has completed.

d Your U2761A is ready for use once the firmware

download has completed.

F. Verify Your Module Connection

The Agilent Connection Expert is one of the utilities in the
IO Libraries. The Connection Expert configures the
connected instruments and enables communication. It is able
to automatically detect the U2761A devices plugged into the
PC.

1 Go to Start > All Programs > Agilent IO Libraries Suite > Agilent

Connection Expert to launch the Connection Expert.

2 The detected U2761A will be visible on the Instrument I/O

on this PC explorer pane. Right-click on the U2761A

instrument on the explorer pane.

U2761A User’s Guide 19

1Getting Started

3 A context menu will appear as shown below and select

Send Commands To This Instrument.

4 The Agilent Interactive IO dialog box will appear. Click Send &

Read to send the *IDN? default command. The
instrument’s response should appear in the Instrument
Session History panel.

5 If the Connection Expert can successfully communicate

with the U2761A, this indicates that the instrument is
installed correctly.

20 U2761A User’s Guide

G. Launch Your Agilent Measurement Manager

NOTE

• The IO Control will launch automatically when you start your PC.

• Launching the Measurement Manager without the IO Control running

will cause failure of the Measurement Manager to detect or establish
any connection with the U2761A connected to your PC.

• To run the IO Control, go to Start > All Programs > Agilent IO
Libraries Suite > Utilities > IO Control.

1 Double-click the Measurement Manager software icon on

your desktop or go to Start > All Programs > Agilent > Modular
Products > Agilent Measurement Manager to launch the

software.

2 The Measurement Manager welcome screen will appear.

Getting Started 1

U2761A User’s Guide 21

1Getting Started

NOTE

3 The Select USB Device dialog box will appear displaying the

connected U2761A devices. To start the application, select
a U2761A device and click OK to establish the connection.

For more information on how to use the Measurement Manager, refer to
the Agilent Measurement Manager help file.

22 U2761A User’s Guide

55-Pin Backplane Connector Pin Configuration

GND

NC

GND

TRIG4

nBPUB

NC

11

GND

NC

TRIG3

GND

CLK10M

NC

10

GND

NC

GND

TRIG5

GND

NC

9

GND

NC

STAR_TRIG

NC

8

TRIG2

GND

GND

NC

GND

TRIG6

GA2

NC

7

GND

NC

TRIG1

GND

GA1

NC

6

GND

NC

GND

TRIG7

GA0

NC

5

GND

NC

TRIG0

GND

NC

NC

4

GND

VBUS

GND

+12 V

+12 V

+12 V

3

GND

GND

GND

+12 V

+12 V

+12 V

2

GND

USB_D

–

USB_D+

GND

+12 V

+12 V

1

F

E

D

C

B

A

The 55-pin backplane connector is used when the U2761A
module is inserted into the U2781A USB modular instrument
chassis. For more details, refer to the Agilent U2781A USB
Modular Instrument Chassis User's Guide.

Getting Started 1

Figure 1-1 55-pin backplane connector pin configuration

Ta b l e 1 - 1 Synchronous Simultaneous Interface (SSI) connector pin

description

SSI timing signal Functionality

GND Ground

NC Not connected

VBUS USB bus power sensing input

USB_D+, USB_D– USB differential pair

TRIG0~TRIG7 Trigger bus

+12 V +12 V power with 4 A current

nBPUB USB backplane input detect

CLK10M 10 MHz clock source

STAR_TRIG Star trigger

GA0,GA1,GA2 Geographical address pin

U2761A User’s Guide 23

1Getting Started

Chassis Installation

The L-mount kit is to be installed to your U2761A module.
The following instructions describe the simple procedure of
installing the L-mount kit and your module in the U2781A
chassis.

1 Unpack the L-mount kit from its packaging.

2 Remove your U2761A module from the bumper casing.

3 Using a Phillips screwdriver, fasten the L-Mount kit to

your U2761A mo du le.

4 Insert your U2761A module into the U2781A chassis with

the 55-pin backplane connector positioned at the bottom
of the module.

5 Once you have slotted the module into the chassis, tighten

the screws of the L-mount kit to secure the connection.

24 U2761A User’s Guide

Agilent U2761A USB Modular Function Generator
User’s Guide

2 Features and Functions

Output Configuration 26
Pulse Waveform 45
Amplitude Modulation (AM) 49
Frequency Modulation (FM) 55
Phase Modulation (PM) 61
Frequency-Shift Keying (FSK) Modulation 66
Phase-Shift Keying (PSK) Modulation 71
Amplitude-Shift Keying (ASK) Modulation 76
Frequency Sweep 80
Tr ig g er i ng 85
Arbitrary Waveforms 91

In this chapter, you will learn about the functions and
features of fered by the U2761A.

25Agilent Technologies

2Features and Functions

Output Configuration

Introduction

Output Function

This section contains the information to help you configure
the U2761A for outputting waveforms. You may not need to
change some of the parameters discussed here, but they are
provided so that you will have accessibility when needed.

The U2761A can output five standard waveforms (Sine,
Square, Ramp, Triangle, and Pulse), and DC. You can select
one of the three built-in Arbitrary waveforms or creat e your
own custom waveforms. In addition, you can internally
modulate Sine, Square, Ramp, Triangle, and Arbitrary
waveforms using AM, FM, PM, FSK, PSK, or ASK. The linear
or logarithmic frequency sweeping is available for Sine,
Square, Ramp, Triangle, and Arbitrary waveforms.

The table below shows which output functions are allowed
with modulation and sweep. Each “V” indicates a valid
combination. If you change to a function that is not
applicable for modulation, or sweep; then the modulation or
mode will be disabled.

Ta b l e 2 - 1 Output functions

Sine Square Ramp Triangle Pulse DC Arbitrary

AM, FM, PM, FSK, PSK, ASK Carrier VVVV V

AM, FM, PM Internal Modulation VVVV V

FSK, PSK, ASK Internal Modulation V

Sweep Mode VVVV V

26 U2761A User’s Guide

Features and Functions 2

Function Limitation

If you change to a function where the maximum frequency is
less than the current function, the frequency will be
adjusted to the maximum value for the new function.

For example, if you are currently outputting a 20 MHz sine
wave and then change to the Ramp function, the U2761A
will automatically adjusts the output frequency to 200 kHz
(the upper limit for Ramp).

Amplitude Limitation

If you change to a function where the maximum amplitude
is less than the current function, the amplitude will
automatically be adjusted to the maximum value for the new
function. This may occur when the output units are Vrms or
dBm due to the differences in crest factor for the various
output functions.

For example, if you output a 2.5 Vrms Square wave (into
50 Ω) and then change to the Sine wave function, the
U2761A will automatically be adjusted the output amplitude
to 1.768 Vrms (the upper limit for Sine wave in Vrms).

U2761A User’s Guide 27

2Features and Functions

Waveform pattern selection

Waveform parameters

Soft Front Panel Operation

The following figure shows the soft front panel of the
U2761A.

28 U2761A User’s Guide

Figure 2-1 U2761A soft front panel

To select a function, click any of the functions on the top
panel as shown below. When a function is selected, the
button will be illuminated.

Figure 2-2 Top panel view of the U2761A

Click Arb to output Arbitrary waveform. Select other
Arbitrary waveform choices from the drop down list

Remote Interface Operation

FUNCtion {SINusoid|SQUare|RAMP|PULSe|DC|USER}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

Output Frequency

Features and Functions 2

.

As shown below, the output frequency range depends on the
function currently selected. The default frequency is 1 kHz for
all functions.

Ta b l e 2 - 2 Output frequency range

Function Minimum frequency Maximum frequency

Sine 1 μHz 20 MHz

Square 1 μHz 20 MHz

Ramp, Triangle 1 μHz 200 kHz

Pulse 500 μHz 5 MHz

DC Not applicable Not applicable

Arbitrary 1 μHz 200 kHz

U2761A User’s Guide 29

2Features and Functions

Function Limitations

If you change to a function where the maximum frequency is
less than the current function, the frequency will be
adjusted to the maximum value for the new function.

For example, if you are currently outputting a 20 MHz sine
wave and then change to the Ramp function, the U2761A
will automatically adjusts the output frequency to 200 kHz
(the upper limit for Ramp).

Duty Cycle Limitations

For Square waveforms, the U2761A may not be able to use
the full range of duty cycle values at higher frequencies as
shown below.

• 20% to 80% (frequency

• 40% to 60% (frequency

If you change to a frequency that cannot produce the
current duty cycle, the duty cycle is automatically adjusted
to the maximum value for the new frequency.

≤ 10 MHz)

> 10 MHz)

For example, if you currently have the duty cycle set to 70%
and then change the frequency to 12 MHz, the U2761A will
automatically adjusts the duty cycle to 60% (the upper limit
for t his frequency).

Soft Front Panel Operation

On the Frequency panel as shown in Figure 2- 3, input the
desired frequency value and select the unit from the drop
down list. To set the waveform period instead, select Period

.

Figure 2-3 Panel view of the frequency section

30 U2761A User’s Guide

Remote Interface Operation

Vpp2 V

maxVoffset

–()×≤

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

Output Amplitude

The default amplitude is 1 Vpp (into 50 Ω) for all functions.

Offset Voltage Limitations

The relation between the output amplitude and offset voltage
is shown below. Vmax is the maximum peak voltage for the
selected output termination (5 V for a 50 Ω load or 10 V for
a high-impedance load).

Features and Functions 2

FREQuency {<frequency>}

Limits Due to Output Termination

If you change the output termination setting, the value of
the output amplitude will be adjusted (and no error will be
generated).

For example, if you set the amplitude to 5 Vpp and then
change the output termination from 50 Ω to “high
impedance”, the amplitude value will double to 10 Vpp. If
you change from “high impedance” to 50 Ω, the displayed
amplitude value will drop to half. For more information, see

“Output Termination” on page 36.

U2761A User’s Guide 31

2Features and Functions

Limits Due to Units Selection

In some cases, the amplitude limits are determined by the
output units selected. This may occur when the units are
Vrms or dBm due to the differences in crest factor for the
various output functions.

For example, if you output a 2.5 Vrms Square wave (into
50 Ω) and then change to the Sine wave function, the
U2761A will automatically adjusts the output amplitude to

1.768 Vrms (the upper limit for Sine wave in Vrms).

You can set the output amplitude in Vpp, Vrms, or dBm. For
more information, see “Output Units” on page 35.

You cannot specify the output amplitude in dBm if the
output termination is set to “high impedance”.

Soft Front Panel Operation

On the Amplitude panel as shown in Figure 2- 4, input the
desired amplitude value and select the unit from the drop
down list.

Figure 2-4 Panel view of the amplitude section

32 U2761A User’s Guide

Remote Interface Operation

V

offsetVmax

V

pp

2

---------–≤

Or, you can set the amplitude by specifying a high level and
low level using the following commands.

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

DC Offset Voltage

The default offset is 0 V for all functions.

Limits Due to Amplitude

The relation between the offset voltage and output amplitude
is shown below. Vmax is the maximum peak voltage for the
selected output termination (5 V for a 50 Ω load or 10 V for
a high-impedance load).

Features and Functions 2

VOLTage {<amplitude>}

VOLTage:HIGH {<voltage>}

VOLTage:LOW {<voltage>}

If the specified offset voltage is not valid, the U2761A will
automatically adjusts it to the maximum DC voltage allowed
with the specified amplitude.

U2761A User’s Guide 33

2Features and Functions

Soft Front Panel Operation

On the Offset panel as shown in Figure 2-5, input the
desired offset value and select the unit from the drop down
list.

Figure 2-5 Panel view of the DC offset section

Remote Interface Operation

VOLTage:OFFSet {<offset>}

Or, you can set the offset by specifying a high level and low
level using the following commands.

VOLTage:HIGH {<voltage>}

VOLTage:LOW {<voltage>}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

34 U2761A User’s Guide

Output Units

Features and Functions 2

This configuration applies to output amplitude only. At
power-on, the units for output amplitude are volts
peak-to-peak.

• The output units consist of Vpp, Vrms, or dBm. The
default unit is Vpp.

• The unit setting is stored in volatile memory. The units
are set to “Vpp” upon power-off or after a remote
interface reset.

• The output units for amplitude cannot be set to dBm if
the output termination is currently set to
“high impedance”. The units are automatically converted
to Vpp.

Soft Front Panel Operation

On the Amplitude panel as shown in Figure 2- 4, input the
desired amplitude value and select the unit from the drop
down list.

Remote Interface Operation

VOLTage:UNIT {VPP|VRMS|DBM}

U2761A User’s Guide 35

2Features and Functions

Output Termination

This configuration applies to output amplitude and offset
voltage only. The U2761A has a fixed series output
impedance of 50 Ω to the device output connector. If the
actual load impedance is different from the specified value,
the amplitude and offset levels will be incorrect.

• The range of the output termination is 1 Ω to 10 kΩ, or
Infinite. The default value is 50

• The output termination setting is stored in volatile
memory and upon power-off or after a remote interface
reset, the setting will return to a default value.

• If you specify a 50 Ω termination but are actually
terminating into an open circuit, the actual output will be
twice the value specified.
For example, if you set the offset to 100 mVDC (and
specify a 50 Ω load) but are terminating the output into
an open circuit, the actual offset will be 200 mVDC.

• If you change the output termination setting, the output
amplitude and offset levels are automatically adjusted (no
error will be generated).
For example, if you set the amplitude to 5 Vpp and then
change the output termination from 50 Ω to “high
impedance”, the amplitude value will double to 10 Vpp. If
you change from “high impedance” to 50 Ω, the displayed
amplitude value will drop to half.

• You cannot specify the output amplitude in dBm if the
output termination is currently set to “high impedance”.
The units are automatically converted to Vpp.

Ω

.

36 U2761A User’s Guide

Features and Functions 2

Soft Front Panel Operation

Click Tools and select Waveform Gen as shown in the following.

Figure 2-6 Panel view of the Tools menu

Then, select the Output Setup tab, input the desired load
impedance value on the Impedance Load panel and select
the unit from the drop down list, or select High Z for
high impedance load.

Remote Interface Operation

OUTPut:LOAD {<ohms>|INFinity|}

U2761A User’s Guide 37

2Features and Functions

20% Duty Cycle 80% Duty Cycle

Duty Cycle (Square Waves)

The duty cycle of a Square wave represents the amount of
time per cycle that the Square wave is at a high level
(assuming that the waveform is not inverted).

Figure 2-7 Square wave duty cycles

Refer to “Pulse Waveform” on page 45 for the information on
the duty cycle for Pulse waveforms.

Duty Cycle

• 20% to 80% (frequency ≤ 10 MHz)

• 40% to 60% (frequency > 10 MHz)

The duty cycle is stored in volatile memory where the duty
cycle is set to default 50% upon power-off or after a remote
interface reset.

The duty cycle setting is stored when you change from
Square wave to another function. Thus, when you return to
the Square function, the previous duty cycle is used.

Limits Due to Frequency

If the Square wave function is selected and you change to a
frequency that cannot produce the current duty cycle, the
duty cycle is automatically adjusted to the maximum value
for the new frequency.

For example, if you currently have the duty cycle set to 70%
and then change the frequency to 12 MHz, the U2761A will
automatically adjusts the duty cycle to 60% (the upper limit
for t his frequency).

38 U2761A User’s Guide

Features and Functions 2

The duty cycle setting does not apply to a Square waveform
used as the modulating waveform for AM, FM, or PM. A 50%
duty cycle is always used for a modulating Square waveform.
The duty cycle setting applies only to a Square waveform
carrier.

Soft Front Panel Operation

After selecting Square at the top panel as shown in

Figure 2- 2, on the Duty Cycle panel below, input the desired

duty cycle value.

Figure 2-8 Panel view of the duty cycle section

Remote Interface Operation

FUNCtion:SQUare:DCYCle{<percent>}

The APPLy command automatically sets the duty cycle to
50%.

U2761A User’s Guide 39

2Features and Functions

0% Symmetry 100% Symmetry

Symmetry (Ramp Wave)

This configuration applies to Ramp wave only. Symmetry
represents the amount of time per cycle that the Ramp wave
is rising (assuming that the waveform is not inverted).

Figure 2-9 Ramp wave duty cycles

• The symmetry percentage is stored in volatile memory
where the symmetry is set to default 100% upon power-off
or after a remote interface reset.

• The symmetry setting is stored when you change from
Ramp wave to another function. Thus, when you return to
the Ramp function, the previous symmetry is used.

• If you select a Ramp waveform as the modulating
waveform for AM, FM, or PM, the symm etry setting does
not apply.

Soft Front Panel Operation

After selecting Ramp at the top panel as shown in

Figure 2- 2, on the Symmetry panel below, input the desired

symmetry value.

Figure 2-10 Panel view of the symmetry section

40 U2761A User’s Guide

Output Control

Features and Functions 2

Remote Interface Operation

FUNCtion:RAMP:SYMMetry{<percent>}

The APPLy command automatically sets the symmetry to
100%.

You can disable or enable the soft front panel output
control. By default, the output is disabled at power-on. When
enabled, the Output button is illuminated.

If an excessive external voltage is applied to the device
output connector, the output will be disabled. To re-enable
the output, remove the overload from the output connector
and click Output to enable the output.

Soft Front Panel Operation

Click Output to enable or disable the output as shown
in Figure 2- 11.

Figure 2-11 Panel view of the output section

U2761A User’s Guide 41

2Features and Functions

Set Output Using SCPI Commands

Remote Interface Operation

OUTPut {OFF|ON}

The APPLy command overrides the current setting and
automatically enables the output control.

The following SCPI commands show a sample procedure of
generating output.

Example 1, To output a DC voltage

-> *CLS; *RST //To reset the U2761A to default

power-on state, this command
can be ignored if this operation
is not required.

-> FUNC DC //Sets the output to DC.

-> VOLT:OFFS 1 //Sets the output DC offset voltage

to 1 VDC.

-> OUTP:LOAD INF //Changes the output termination

to infinity.

-> OUTP ON //Turns on output.

42 U2761A User’s Guide

Features and Functions 2

Example 2, To output a Sine wave

-> *CLS; *RST //To reset the U2761A to default

power-on state, this command can
be ignored if this operation is not
required.

-> FUNC SIN //Sets the output to Sine wave.

-> VOLT 5 VPP //Sets the output amplitude to 5 Vpp.

-> FREQ 1000 //Sets the output frequency to 1 kHz.

-> VOLT:OFFS 0 //Sets the output offset to 0.

-> OUTP ON //Turns on output.

Example 3, To output a Square wave

-> *CLS; *RST //To reset the U2761A to

default power-on state,
this command can be
ignored if this operation
is not required.

-> APPL:SQU 2000,5 VPP,0 //Sets the output to Square

wave, frequency 2 kHz,
amplitude
5 Vpp, offset 0.

-> FUNC:SQU:DCYC 30 //Changes the duty cycle to

30%.

-> OUTP ON //Turns on output.

U2761A User’s Guide 43

2Features and Functions

Example 4, To output a Ramp wave

-> *CLS; *RST //To reset the U2761A to default

power-on state, this command
can be ignored if this operation
is not required.

-> FUNC RAMP // Sets the output to Ramp wave.

-> VOLT 5 VPP //Sets the output amplitude to

5 Vpp.

-> FREQ 10000 //Sets the output frequency to

10 kHz.

-> VOLT:OFFS 0 //Sets the output offset to 0.

-> FUNC:RAMP:SYMM 50 //Changes the symmetry to 50%.

-> OUTP ON //Turns on output.

44 U2761A User’s Guide

Pulse Waveform

Pulse width

Period

90% 90%

50% 50%

10%

10%

Rise time Fall time

Features and Functions 2

As shown below, a Pulse waveform consists of a period, a
pulse width, a rising edge, and a falling edge.

Figure 2-12 Pulse waveform

Pulse Period

The range of the pulse period is from 200 ns to 2000 s. The
default value is 1 ms. The U2761A will adjusts the pulse

width as necessary to accommodate the specified period.

Soft Front Panel Operation

After selecting Pulse at the top panel as shown in

Figure 2- 2, on the Frequency panel as shown in Figure 2- 3,

select Period , input the desired pulse period value,
and then select the unit from the drop down list.

U2761A User’s Guide 45

Remote Interface Operation

PULSe:PERiod{<seconds>}

2Features and Functions

Pulse Width

The pulse width represents the time from the 50% threshold
of the pulse’s rising edge to the 50% threshold of the next
falling edge.

• The range of the pulse width is 40 ns to <2000 s (see
restrictions below). The default pulse width is 500

• The minimum pulse width (Wmin) is affected by the
period.

Wmin = 40 ns for period ≤ 10 s

Wmin = 200 ns for period > 10 s, but ≤ 100 s

Wmin = 2 μs for period > 100 s, but ≤ 1000 s

Wmin = 20 μs for period > 1000 s

• The specified pulse width must also be less than the
difference between the period and the minimum pulse
width as shown in the equation below. The U2761A will
adjusts the pulse width as necessary to accommodate the
specified period.

Pulse Width

≤

Period – Wmin

μ

s.

Soft Front Panel Operation

After selecting Pulse at the top panel as shown in

Figure 2- 2, on the Width panel below, input the desired

pulse width value and select the unit from the drop down
list.

Figure 2-13 Panel view of the pulse width section

Remote Interface Operation

FUNCtion:PULSe:WIDTh{<seconds>}

46 U2761A User’s Guide

Pulse Duty Cycle

The pulse duty cycle is defined as:

Duty Cycle = 100

where the pulse width represents the time from the 50%
threshold of the rising edge of the pulse to the 50%
threshold of the next falling edge.

• Pulse duty cycle: >0% to <100% (see restrictions below).
The default is 50%.

• The specified pulse duty cycle must conform to the
following restrictions determined by the minimum pulse
width (Wmin). The U2761A will adjust the pulse duty
cycle as needed to accommodate the specified period.

and

where:

Features and Functions 2

×

Pulse Width / Period

Duty Cycle

Duty Cycle

Wmin = 40 ns for period ≤ 10 s.

Wmin = 200 ns for period > 10 s, but ≤ 100 s.

Wmin = 2 μs for period > 100 s, but ≤ 1000 s.

Wmin = 20 μs for period > 1000 s.

≥

100 × Wmin / Period

≤

100 × (1 – Wmin / Period)

Soft Front Panel Operation

After selecting Pulse at the top panel as shown in

Figure 2- 2, select Duty Cycle as shown in
Figure 2- 13 and input the desired pulse duty cycle value on

the Duty Cycle panel.

Remote Interface Operation

FUNCtion:PULSe:DCYCle{<percent>}

U2761A User’s Guide 47

2Features and Functions

Generate Pulse Waveform Using SCPI Commands

Example 1

-> *CLS; *RST //To reset the U2761A to default

power-on state, this command
can be ignored if this operation
is not required.

-> FUNC PULS // Sets the output to Pulse wave.

-> VOLT 5 VPP //Sets the output amplitude to

5 Vpp.

-> VOLT:OFFS 0 //Sets the output offset to 0.

-> PULS:PER 1 //Sets the pulse period to 1 s.

-> FUNC:PULS:DCYC 50 //Set the pulse duty cycle to 50%.

-> OUTP ON //Turns on output.

48 U2761A User’s Guide

Amplitude Modulation (AM)

Modulating frequency

AM depth

A modulated waveform consists of a carrier waveform and a
modulating waveform. An example of the AM waveform is
shown in Figure 2- 14. In AM, the amplitude of the carrier is
varied by the instantaneous voltage of the modulating
waveform. The amount of amplitude modulation is called the
modulation depth which refers to the portion of the
amplitude range that will be used by the modulation.

Features and Functions 2

Figure 2-14 AM waveform

To Select AM

The U2761A allows only one modulation mode at a time. The
U2761A does not allow modulation when sweep is enabled.

U2761A User’s Guide 49

2Features and Functions

Soft Front Panel Operation

Click Mod and then select AM as shown in

Figure 2- 15. To output the AM waveform, configure the

settings for the carrier frequency, modulating frequency,
depth, output amplitude, offset voltage, and the desired
waveform.

Figure 2-15 Panel view of AM

Remote Interface Operation

AM:STATe {OFF|ON}

Carrier Waveform

The AM carrier waveform consists of Sine, Square, Ramp,
Triangle, or Arbitrary waveform. The default waveform is
Sine wave. You cannot use Pulse or DC as the carrier
waveform.

Soft Front Panel Operation

For Arbitrary waveform, select Arb at the top panel
as shown in Figure 2-2 and then select the desired
waveform from the drop down list as shown in

Figure 2- 16.

50 U2761A User’s Guide

Features and Functions 2

Figure 2-16 Panel view of the Arbitrary waveform

Remote Interface Operation

FUNCtion {SINusoid|SQUare|RAMP|USER}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

Carrier Frequency

The maximum carrier frequency depends on the selected
function as shown below. The default frequency is 1 kHz for

all functions.

Ta b l e 2 - 3 Carrier frequency for AM

Function Minimum frequency Maximum frequency

Sine 1 μHz 20 MHz

Square 1 μHz 20 MHz

Ramp, Triangle 1 μHz 200 kHz

Arbitrary 1 μHz 200 kHz

U2761A User’s Guide 51

2Features and Functions

Modulating Waveform

Soft Front Panel Operation

On the Frequency panel as shown in Figure 2- 3, input the
desired frequency value and select the unit from the drop
down list.

Remote Interface Operation

FREQuency {<frequency>}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

The modulating waveform consists of Sine, Square, Ramp,
Negative Ramp (Nramp), Triangle, or Arbitrary waveform.
The default modulating waveform is Sine wave.

• Square has 50% duty cycle

• Ramp has 100% symmetry

• Triangle has 50% symmetry

• Negative Ramp has 0% symmetry

Soft Front Panel Operation

Select the desired modulating waveform from the drop down
list as shown in Figure 2- 15.

Remote Interface Operation

AM:INTernal:FUNCtion

{SINusoid|SQUare|RAMP|NRAMp|TRIangle|USER}

52 U2761A User’s Guide

Modulating Waveform Frequency

NOTE

The range of the modulating waveform frequency is 2 mHz
to 20 kHz. The default modulating waveform frequency is
100 Hz.

Soft Front Panel Operation

On the Mod Frequency panel as shown in Figure 2- 15, input
the desired modulating frequency value and select the unit
from the drop down list.

Remote Interface Operation

AM:INTernal:FREQuency {<frequency>}

Modulation Depth

The modulation depth is expressed in percentage and
represents the extent of the amplitude variation. At 0%
depth, the output amplitude is half of the selected value. At
100% depth, the output amplitude equals the selected value.

Features and Functions 2

The range of the modulation depth is 0% to 100%. The
default modulation depth is 100%.

At 100% depth, the maximum output of the U2761A will not exceed ±2.5 V
peak (into a 50 Ω load).

Soft Front Panel Operation

On the Depth panel as shown in Figure 2- 15, select the
desired modulating depth value from the drop down list.

Remote Interface Operation

AM:DEPTh {<depth in percent>}

U2761A User’s Guide 53

2Features and Functions

Generate AM Using SCPI Commands

Example 1

-> *CLS; *RST //To reset the U2761A to default

power-on state, this command
can be ignored if this operation
is not required.

-> AM:STAT ON //Enables AM.

-> FUNC SQU //Sets the carrier waveform to

Square wave.

-> FREQ 2000 // Sets the carrier frequency to

2 kHz.

-> VOLT 5 VPP //Sets the output amplitude to

5 Vpp.

-> VOLT:OFFS 0 //Sets the output offset to 0.

-> AM:INT:FUNC SIN //Changes the modulating

waveform shape to Sine wave.

-> AM:INT:FREQ 500 //Changes the modulating

frequency to 500 Hz.

-> AM:DEPT 50 //Changes the modulation depth

to 50%.

-> OUTP ON //Turns on output.

54 U2761A User’s Guide

Frequency Modulation (FM)

Modulating frequency

FM deviation

A modulated waveform consists of a carrier waveform and a
modulating waveform. Below shows an example of the FM
waveform. In FM, the frequency of the carrier is varied by
the instantaneous voltage of the modulating waveform. The
variation in frequency of the modulated waveform from the
carrier frequency is called the frequency deviation.

Features and Functions 2

Figure 2-17 FM waveform

To Selec t FM

The U2761A allows only one modulation mode to be enabled
at a time. The U2761A does not allow FM to be enabled at
the same time that sweep is enabled.

U2761A User’s Guide 55

2Features and Functions

Soft Front Panel Operation

Click Mod and then select FM as shown in

Figure 2- 18. To output the FM waveform, configure the

settings for the carrier frequency, output amplitude, offset
voltage, modulating frequency, deviation, and the desired
waveform.

Figure 2-18 Panel view of FM

Remote Interface Operation

FM:STATe {OFF|ON}

Carrier Waveform

The FM carrier waveform consists of Sine, Square, Ramp,
Triangle, or Arbitrary waveform. The default waveform is
Sine wave. You cannot use Pulse or DC as the carrier
waveform.

Soft Front Panel Operation

For Arbitrary waveforms, select Arb at the top panel
as shown in Figure 2-2 and select the desired waveform
from the drop down list as shown in

Figure 2- 16.

56 U2761A User’s Guide

Remote Interface Operation

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

Carrier Frequency

The maximum carrier frequency depends on the selected
function as shown below. The default is 1 kHz for all

functions.

Ta b l e 2 - 4 Carrier frequency for FM

Function Minimum frequency Maximum frequency

Sine 1 μHz 20 MHz

Square 1 μHz 20 MHz

Features and Functions 2

FUNCtion {SINusoid|SQUare|RAMP|USER}

Ramp, Triangle 1 μHz 200 kHz

Arbitrary 1 μHz 200 kHz

The carrier frequency must always be greater than or equal
to the frequency deviation plus 1 μHz. If you attempt to set
the deviation to a value plus 1 μHz greater than the carrier
frequency (with FM enabled), the U2761A will automatically
adjusts the deviation to the maximum value allowed with the
present carrier frequency.

The sum of the carrier frequency and deviation must be less
than or equal to the maximum frequency for the selected
function (20 MHz for Sine and Square, and 200 kHz for
Ramp and Arbitrary waveforms). If you attempt to set the
deviation to a value that is not valid, the U2761A will
automatically adjusts it to the maximum value allowed with
the present carrier frequency.

U2761A User’s Guide 57

2Features and Functions

Modulating Waveform

Soft Front Panel Operation

On the Frequency panel as shown in Figure 2- 3, input the
desired frequency value and select the unit from the drop
down list.

Remote Interface Operation

FREQuency {<frequency>}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

The modulating waveform consists of Sine, Square, Ramp,
Negative Ramp (Nramp), Triangle, Noise, or Arbitrary
waveform. The default modulating waveform is Sine wave.

• Square has 50% duty cycle

• Ramp has 100% symmetry

• Triangle has 50% symmetry

• Negative Ramp has 0% symmetry

Soft Front Panel Operation

Select the desired modulating waveform from the drop down
list as shown in Figure 2-18.

Remote Interface Operation

FM:INTernal:FUNCtion

{SINusoid|SQUare|RAMP|NRAMp|TRIangle|USER}

58 U2761A User’s Guide

Modulating Waveform Frequency

The range of the modulating waveform frequency is 2 mHz
to 20 kHz. The default modulating waveform frequency is
100 Hz.

Soft Front Panel Operation

On the Mod Frequency panel as shown in Figure 2- 18, input
the desired modulating frequency value and select the unit
from the drop down list.

Remote Interface Operation

FM:INTernal:FREQuency {<frequency>}

Frequency Deviation

The frequency deviation setting represents the peak variation
in frequency of the modulated waveform from the carrier
frequency.

Features and Functions 2

The range of the frequency deviation is 1 Hz to 500 kHz
(limited to 100 kHz minus 1 μHz for Ramp and Arbitrary
waveforms). The default frequency deviation is 100 Hz.

The carrier frequency must always be greater than or equal
to the frequency deviation plus 1 μHz. If you attempt to set
the deviation to a value plus 1 μHz greater than the carrier
frequency (with FM enabled), the U2761A will automatically
adjusts the deviation to the maximum value allowed with the
present carrier frequency.

The sum of the carrier frequency and deviation must be less
than or equal to the maximum frequency for the selected
function (20 MHz for Sine and Square, and 200 kHz for
Ramp and Arbitrary waveforms). If you attempt to set the
deviation to a value that is not valid, the U2761A will
automatically adjusts it to the maximum value allowed with
the present carrier frequency.

U2761A User’s Guide 59

2Features and Functions

Generate FM Using SCPI Commands

Soft Front Panel Operation

On the Deviation panel as shown in Figure 2- 18, input the
desired frequency deviation value and select the unit from
the drop down list.

Remote Interface Operation

FM:DEViation {<peak deviation in Hz>}

Example 1

-> *CLS; *RST //To reset the U2761A to default

power-on state, this command
can be ignored if this operation
is not required.

-> FM:STAT ON //Enables FM.

-> FUNC SIN //Sets the carrier waveform to

Sine wave.

-> FREQ 1000 // Sets the carrier frequency to

1 kHz.

-> VOLT 5 VPP //Sets the output amplitude to

5 Vpp.

-> VOLT:OFFS 0 //Sets the output offset to 0.

-> FM:INT:FUNC SIN //Changes the modulating

waveform shape to Sine wave.

-> FM:INT:FREQ 500 //Changes the modulating

frequency to 500 Hz.

-> FM:DEV 100 //Changes the frequency

deviation to 100 Hz.

-> OUTP ON //Turns on output.

60 U2761A User’s Guide

Phase Modulation (PM)

Modulating frequency

Phase deviation

A modulated waveform consists of a carrier waveform and a
modulating waveform . The following figure shows an example
of a PM waveform. PM is very similar to FM, but in PM, the
phase of the modulated waveform is varied by the
instantaneous voltage of the modulating waveform. The
variation in phase of the modulated waveform from the
carrier waveform is called the phase deviation.

Features and Functions 2

Figure 2-19 PM waveform

To Selec t P M

The U2761A allows only one modulation mode to be enabled
at a time. The U2761A does not allow PM to be enabled at
the same time that sweep is enabled.

U2761A User’s Guide 61

2Features and Functions

Soft Front Panel Operation

Click Mod and then select PM as shown in

Figure 2- 20. To output the PM waveform, configure the

settings for the carrier frequency, output amplitude, offset
voltage, modulating frequency, phase deviation, and the
desired waveform.

Figure 2-20 Panel view of PM

Remote Interface Operation

PM:STATe {OFF|ON}

Carrier Waveform

The PM carrier waveform consists of Sine, Square, Ramp,
Triangle, or Arbitrary waveform. The default waveform is
Sine wave. You cannot use Pulse or DC as the carrier
waveform.

Soft Front Panel Operation

For Arbitrary waveforms, click Arb at the top panel
as shown in Figure 2-2 and select the desired waveform
from the drop down list as shown in Figure 2- 16.

62 U2761A User’s Guide

Remote Interface Operation

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

Carrier Frequency

The maximum carrier frequency depends on the function
selected as shown below. The default carrier frequency is
1 kHz for all functions.

Ta b l e 2 - 5 Carrier frequency for PM

Function Minimum frequency Maximum frequency

Sine 1 μHz 20 MHz

Square 1 μHz 20 MHz

Features and Functions 2

FUNCtion {SINusoid|SQUare|RAMP|USER}

Ramp, Triangle 1 μHz 200 kHz

Arbitrary 1 μHz 200 kHz

Soft Front Panel Operation

On the Frequency panel as shown in Figure 2- 3, input the
desired frequency value and select the unit from the drop
down list.

Remote Interface Operation

FREQuency {<frequency>}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

U2761A User’s Guide 63

2Features and Functions

Modulating Waveform

The modulating waveform consists of Sine, Square, Ramp,
Negative Ramp (Nramp), Triangle, or Arbitrary waveform.
The default waveform is Sine wave.

• Square has 50% duty cycle

• Ramp has 100% symmetry

• Triangle has 50% symmetry

• Negative Ramp has 0% symmetry

Soft Front Panel Operation

Select the desired modulating waveform from the drop down
list as shown in Figure 2- 20.

Remote Interface Operation

PM:INTernal:FUNCtion

{SINusoid|SQUare|RAMP|NRAMp|TRIangle|USER}

Modulating Waveform Frequency

The range of the modulating waveform frequency is 2 mHz
to 20 kHz. The default modulating waveform frequency is
10 Hz.

Soft Front Panel Operation

On the Mod Frequency panel as shown in Figure 2- 20, input
the desired modulating frequency value and select the unit
from the drop down list.

Remote Interface Operation

PM:INTernal:FREQuency {<frequency>}

64 U2761A User’s Guide

Phase Deviation

The phase deviation setting represents the peak variation in
phase of the modulated waveform from the carrier
waveform. The phase deviation setting can be set from
0 to 360 °. The default phase deviation setting is 180

Soft Front Panel Operation

On the Phase Deviation panel as shown in Figure 2- 20,
input the desired phase deviation value.

Remote Interface Operation

PM:DEViation {<deviation in degrees>}

Generate PM Using SCPI Commands

Example 1

Features and Functions 2

°

.

-> *CLS; *RST //To reset the U2761A to default

power-on state, this command
can be ignored if this operation
is not required.

-> PM:STAT ON //Enables PM.

-> FUNC SIN //Sets the carrier waveform to

Sine wave.

-> FREQ 1000 // Sets the carrier frequency to

1 kHz.

-> VOLT 5 VPP //Sets the output amplitude to

5 Vpp.

-> VOLT:OFFS 0 //Sets the output offset to 0.

-> PM:INT:FUNC SIN //Changes the modulating

waveform shape to Sine wave.

-> PM:INT:FREQ 500 //Changes the modulating

frequency to 500 Hz.

-> PM:DEV 180 //Changes the phase deviation to

180 °.

-> OUTP ON //Turns on output.

U2761A User’s Guide 65

2Features and Functions

FSK rate

Hop frequency

Frequency-Shift Keying (FSK) Modulation

FSK is similar to FM except that the frequency alternates
between two preset values. You can configure the U2761A to
“shift” its output frequency between two preset values using
FSK modulation. An example of the FSK modulation
waveform is shown below. The rate at which the output
shifts between the two frequencies (called the “carrier
frequency” and the “hop frequency”) is determined by the
internal rate generator.

Figure 2-21 FSK modulation waveform

To Select FSK Modulation

The U2761A allows only one modulation mode to be enabled
at a time. The U2761A does not allow FSK to be enabled at
the same time that sweep is enabled.

66 U2761A User’s Guide

Features and Functions 2

Soft Front Panel Operation

Click Mod and select FSK as shown in

Figure 2- 22. To output the FSK waveform, configure the

settings for the carrier frequency, output amplitude, offset
voltage, “hop frequency”, and FSK rate.

Figure 2-22 Panel view of FSK

Remote Interface Operation

FSKey:STATe {OFF|ON}

Carrier Waveform

The FSK carrier waveform consists of Sine, Square, Ramp,
Triangle, or Arbitrary waveform. The default carrier
waveform is Sine wave. You cannot use Pulse or DC as the
carrier waveform.

Soft Front Panel Operation

For Arbitrary waveforms, click Arb at the top panel
as shown in Figure 2-2 and select the desired waveform
from the drop down list as shown in

Figure 2- 16.

U2761A User’s Guide 67

2Features and Functions

FSK Carrier Frequency

Remote Interface Operation

FUNCtion {SINusoid|SQUare|RAMP|USER}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

The maximum carrier frequency depends on the function
selected as shown below. The default carrier frequency is
1 kHz for all functions.

Ta b l e 2 - 6 Carrier frequency for FSK

Function Minimum frequency Maximum frequency

Sine 1 μHz 20 MHz

Square 1 μHz 20 MHz

Ramp, Triangle 1 μHz 200 kHz

Arbitrary 1 μHz 200 kHz

Soft Front Panel Operation

On the Frequency panel as shown in Figure 2- 3, input the
desired frequency value and select the unit from the drop
down list.

Remote Interface Operation

FREQuency {<frequency>}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

68 U2761A User’s Guide

FSK “Hop” Frequency

The maximum alternate (or “hop”) frequency depends on the
function selected as shown below. The default “hop”
frequency is 100 Hz for all functions.

Ta b l e 2 - 7 “Hop” frequency

Function Minimum frequency Maximum frequency

Sine 1 μHz 20 MHz

Square 1 μHz 20 MHz

Ramp, Triangle 1 μHz 200 kHz

Arbitrary 1 μHz 200 kHz

Only Square wave with a 50% duty cycle is available for the
Internal FSK modulating waveform.

Soft Front Panel Operation

Features and Functions 2

On the Hop Frequency panel as shown in Figure 2- 22, input
the desired hop frequency value and select the unit from the
drop down list.

Remote Interface Operation

FSKey:FREQuency {<frequency>}

U2761A User’s Guide 69

2Features and Functions

FSK Rate

Generate FSK Modulation Using SCPI Commands

The FSK rate is the rate at which the output frequency
“shifts” between the carrier frequency and the hop
frequency.

• The range of the FSK rate is 2 mHz to 100 kHz. The
default FSK rate value is 10 Hz.

Soft Front Panel Operation

On the FSK Rate panel as shown in Figure 2- 22, input the
desired FSK rate value and select the unit from the drop
down list.

Remote Interface Operation

FSKey:INTernal:RATE {<rate in Hz>}

Example 1

-> *CLS; *RST //To reset the U2761A to default

power-on state, this command
can be ignored if this operation
is not required.

-> FSK:STAT ON //Enables FSK modulation.

-> FUNC SIN //Sets the carrier waveform to

Sine wave.

-> FREQ 1000 // Sets the carrier frequency to

1 kHz.

-> VOLT 5 VPP //Sets the output amplitude to

5 Vpp.

-> VOLT:OFFS 0 //Sets the output offset to 0.

-> FSK:FREQ 100 //Sets the "hop" frequency to

100 Hz.

-> FSK:INT:RATE 10 //Sets the FSK rate to 10 Hz.

-> OUTP ON //Turns on output.

70 U2761A User’s Guide

Phase-Shift Keying (PSK) Modulation

PSK rate

PSK deviation

Phase-shift keying (PSK) is a form of digital modulation in
which the phase of the carrier signal is discretely varied.
You can configure the U2761A to “shift” its output phase
between two preset phases using PSK. The rate at which the
output shifts between the two phases is determined by the
internal rate generator on the signal level. The following
figure shows an example of the PSK modulation waveform.

Features and Functions 2

Figure 2-23 PSK modulation waveform

To Select PSK Modulation

The U2761A allows only one modulation mode to be enabled
at a time. The U2761A does not allow PSK to be enabled at
the same time that sweep is enabled.

U2761A User’s Guide 71

2Features and Functions

Soft Front Panel Operation

Click Mod and then select PSK as shown in

Figure 2- 24. To output the PSK waveform, configure the

settings for the carrier frequency, output amplitude, offset
voltage, deviation, and PSK rate.

Figure 2-24 Panel view of PSK

Remote Interface Operation

PSKey:STATe {OFF|ON}

Carrier Waveform

The PSK carrier waveform consists of Sine, Square, Ramp,
Triangle, or Arbitrary waveform. The default waveform is
Sine wave. You cannot use Pulse or DC as the carrier
waveform.

Soft Front Panel Operation

For Arbitrary waveforms, select Arb at the top panel
as shown in Figure 2-2 and select the desired waveform
from the drop down list as shown in

Figure 2- 16.

72 U2761A User’s Guide

Remote Interface Operation

FUNCtion {SINusoid|SQUare|RAMP|USER}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

PSK Carrier Frequency

The maximum carrier frequency depends on the function
selected as shown below. The default is 1 kHz for all functions.

Ta b l e 2 - 8 Carrier frequency for PSK

Function Minimum frequency Maximum frequency

Sine 1 μHz 20 MHz

Square 1 μHz 20 MHz

Ramp, Triangle 1 μHz 200 kHz

Features and Functions 2

Arbitrary 1 μHz 200 kHz

Only Square wave with a 50% duty cycle is available for the
Internal PSK modulating waveform.

Soft Front Panel Operation

On the Frequency panel shown in Figure 2- 3, input the
desired frequency value and select the unit from the drop
down list.

Remote Interface Operation

FREQuency {<frequency>}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

U2761A User’s Guide 73

2Features and Functions

PSK Rate

PSK Deviation

The PSK rate is the rate at which the output phase “shifts”
between two preset phases. The range of the PSK rate is 2
mHz to 100 kHz. The default PSK rate value is 10 Hz.

Soft Front Panel Operation

On the PSK Rate panel as shown in Figure 2- 24, input the
desired PSK rate value and select the unit from the drop
down list.

Remote Interface Operation

PSKey:INTernal:RATE {<rate in Hz>}

The deviation setting represents the phase variation of the
shifted waveform from the carrier waveform. The deviation
can be set from 0 to 360 °. The default deviation setting is

180

°

.

Soft Front Panel Operation

On the Deviation panel as shown in Figure 2- 24, input the
desired deviation value.

Remote Interface Operation

PSKey:DEViation {<deviation in degrees>}

74 U2761A User’s Guide

Features and Functions 2

Generate PSK Modulation Using SCPI Commands

Example 1

-> *CLS; *RST //To reset the U2761A to

default power-on state, this
command can be ignored if
this operation is not
required.

-> PSK:STAT ON //Enables PSK modulation.

-> FUNC SIN //Sets the carrier waveform to

Sine wave.

-> FREQ 1000 //Sets the carrier frequency to

1 kHz.

-> VOLT 5 VPP //Sets the output amplitude to

5 Vpp.

-> VOLT:OFFS 0 //Sets the output offset to 0.

-> PSK:INT:RATE 10 //Sets the PSK rate to

10 Hz.

-> PSK:DEV 180 //Sets the PSK deviation to

180 °.

-> OUTP ON //Turns on output.

U2761A User’s Guide 75

2Features and Functions

ASK rate

Amplitude-Shift Keying (ASK) Modulation

ASK is a form of digital modulation in which the modulating
signal apply variations in the amplitude of a carrier signal.
The amplitude of the carrier signal varies simultaneously
with the modulating signal while phase and frequency
remain constant. In other words, the carrier signal can be
assumed as an on and off switch. You can configure the
U2761A to “shift” its output amplitude between two preset
amplitudes using ASK. The rate at which the output shifts
between the two amplitudes is determined by the internal
rate generator. An example of the ASK modulation waveform
is shown in the following.

Figure 2-25 ASK modulation waveform

To Select ASK Modulation

The U2761A allows only one modulation mode to be enabled
at a time. The U2761A does not allow ASK to be enabled at
the same time that sweep is enabled.

76 U2761A User’s Guide

Features and Functions 2

Soft Front Panel Operation

Click Mod and then select ASK as shown in

Figure 2- 26. To output the ASK waveform, configure the

settings for the carrier frequency, output amplitude, offset
voltage, and ASK rate.

Figure 2-26 Panel view of ASK

Remote Interface Operation

ASKey:STATe {OFF|ON}

Carrier Waveform

The ASK carrier waveform consists of Sine, Square, Ramp,
Triangle, or Arbitrary waveform. The default waveform is
Sine wave. You cannot use Pulse or DC as the carrier
waveform.

Soft Front Panel Operation

For Arbitrary waveforms, select Arb at the top panel
as shown in Figure 2-2 and select the desired waveform
from the drop down list as shown in

Figure 2- 16.

U2761A User’s Guide 77

2Features and Functions

Carrier Frequency

Remote Interface Operation

FUNCtion {SINusoid|SQUare|RAMP|USER}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

The maximum carrier frequency depends on the function
selected as shown below. The default is 1 kHz for all functions.

Ta b l e 2 - 9 Carrier frequency for ASK

Function Minimum frequency Maximum frequency

Sine 1 μHz 20 MHz

Square 1 μHz 20 MHz

Ramp, Triangle 1 μHz 200 kHz

Arbitrary 1 μHz 200 kHz

Only Square wave with a 50% duty cycle is available for the
Internal ASK modulating waveform.

Soft Front Panel Operation

On the Frequency panel as shown in Figure 2- 3, input the
desired frequency value and select the unit from the drop
down list.

Remote Interface Operation

FREQuency {<frequency>}

You can also use the APPLy command to select the function,
frequency, amplitude, and offset.

78 U2761A User’s Guide

Features and Functions 2

ASK Rate

The ASK rate is the rate at which the output amplitude
“shifts” between two preset amplitudes. The range of the
ASK rate is 2 mHz to 100 kHz. The default ASK rate value is
10 Hz.

Soft Front Panel Operation

On the ASK Rate panel as shown in Figure 2- 26, input the
desired ASK rate value and select the unit from the drop
down list.

Remote Interface Operation

ASKey:INTernal:RATE {<rate in Hz>}

Generate ASK Modulation Using SCPI Commands

Example 1

-> *CLS; *RST //To reset the U2761A to

default power-on state, this
command can be ignored if
this operation is not
required.

-> ASK:STAT ON //Enables ASK modulation.

-> FUNC SIN //Sets the carrier waveform to

Sine wave.

-> FREQ 1000 //Sets the carrier frequency to

1 kHz.

-> VOLT 5 VPP // Sets the output amplitude to

5 Vpp.

-> VOLT:OFFS 0 //Sets the output offset to 0.

-> ASK:INT:RATE 10 //Sets the ASK rate to

10 Hz.

-> OUTP ON //Turns on output.

U2761A User’s Guide 79

2Features and Functions

Frequency

Linear type

Start frequency

Stop frequency

Frequency Sweep

In the frequency sweep mode, the U2761A “steps” from the
start frequency to the stop frequency at a sweep rate which
you specify. You can sweep up or down in frequency, and
with either linear or logarithmic spacing. You can also
configure the U2761A to output a single sweep (one pass
from start frequency to stop frequency) by applying an
External or Manual (software) trigger. The U2761A can
produce a frequency sweep for Sine, Square, Ramp, Triangle,
or Arbitrary’s waveform (Pulse and DC are not allowed). The
figure below shows an example of the frequency sweep.

Figure 2-27 Frequency sweep

To Select Sweep

The U2761A does not allow the sweep mode to be enabled at
the same time that any modulation mode is enabled.

Soft Front Panel Operation

Click Sweep as shown in Figure 2- 28. To output
sweep, configure the settings for frequencies, output
amplitude, offset, sweep type and time, and trigger setup.

80 U2761A User’s Guide

Figure 2-28 Panel view of sweep

Remote Interface Operation

SWEep:STATe {OFF|ON}

Start Frequency and Stop Frequency

Features and Functions 2

The start frequency and stop frequency set the upper and
lower frequency bounds for the sweep. The U2761A begins at
the start frequency, sweeps to the stop frequency, and then
resets back to the start frequency.

• The range of the start and stop frequencies is 1 μHz to
20 MHz (limited to 200 kHz for Ramp and Arbitrary
waveforms). The sweep is phase-continuous over the full
frequency range. The default start frequency is 100 Hz. The

default stop frequency is 1 kHz.

• To sweep up in frequency, set the start frequency < stop
frequency. To sweep down in frequency, set the start
frequency > stop frequency.

Soft Front Panel Operation

On the Start Frequency and Stop Frequency panels as
shown in Figure 2- 28, input the desired start frequency and
stop frequency values and select the respective units from
the drop down lists.

U2761A User’s Guide 81

2Features and Functions

Sweep Mode

Remote Interface Operation

FREQuency:STARt {<frequency>}

FREQuency:STOP {<frequency>}

You can sweep with either linear or logarithmic spacing. For
a linear sweep, the U2761A varies the output frequency in a
linear fashion during the sweep. For a logarithmic sweep,
the U2761A varies the output frequency in a logarithmic
fashion.

The sweep mode consists of Linear or Logarithmic. The
default sweep mode is Linear.

Soft Front Panel Operation

On the Sweep Type panel as shown in Figure 2- 28, select
the Linear or Log mode.

Remote Interface Operation

SWEep:SPACing {LINear|LOGarithmic}

Sweep Time

The sweep time specifies the number of seconds required to
sweep from the start frequency to the stop frequency. The
number of discrete frequency points in the sweep is
automatically calculated by the U2761A and is based on the
sweep time you have selected. The range of the sweep time
is 1 ms to 500 s. The default sweep time is 1 s.

82 U2761A User’s Guide