Spirent GSS6100 User's Guide

DGP000814AAA Issue: 2-01 July 2007

GSS6100 AND SIMCHAN USER MANUAL

THE INFORMATION CONTAINED IN THIS DOCUMENT IS THE PROPERTY OF SPIRENT COMMUNICATIONS PLC. EXCEPT AS SPECIFICALLY AUTHORISED IN WRITING BY SPIRENT SPIRENT COMMUNICATIONS PLC, THE HOLDER OF THIS DOCUMENT SHALL KEEP ALL INFORMATION CONTAINED HEREIN CONFIDENTIAL AND SHALL PROTECT SAME IN WHOLE OR IN PART FROM DISCLOSURE AND DISSEMINATION TO ALL THIRD PARTIES TO THE SAME DEGREE IT PROTECTS ITS OWN CONFIDENTIAL INFORMATION. © SPIRENT COMMUNICATIONS PLC 2005-2007

PROPRIETARY INFORMATION

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About this publication

Purpose

This document provides all information for installing and using SimCHAN software on a Windows XP PC.

This document provides all information for the installation and operation of the GSS6100 signal generator using both SimCHAN software and the remote command set.

Audience

This document is intended for all users of the GSS6100 signal generator and SimCHAN software.

In this document:

References to Spirent refer to Spirent Communications - Performance Analysis & Wireless Positioning (Spirent Communications PA-WP), unless otherwise stated.

GPS is used as a generic term for any of the satellite navigation systems supported by the Spirent range of Satellite Navigation Simulator products.

A specific satellite navigation system is referred to by its name.

GSS6100 and SimCHAN user manual © Spirent Communications Plc 2005 - 2007

About

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CONTENTS

ABOUT THIS PUBLICATION.................................................................................................................I

CHAPTER 1: GENERAL ......................................................................................................................1-1

1.1 RECORD OF ISSUE 1-1

1.2 REFERENCED DOCUMENTS 1-2

1.3 DELIVERABLES 1-2

1.4 COPYRIGHT NOTICES 1-2

1.5 ACRONYMS AND ABBREVIATIONS 1-3

1.5.1 Document conventions ................................................................................... 1-5

CHAPTER 2: INTRODUCTION..........................................................................................................2-1

2.1 SIMCHAN OR REMOTE OPERATION 2-1

CHAPTER 3: HARDWARE OVERVIEW AND INSTALLATION ................................................3-1

3.1 FRONT PANEL 3-1

3.2 REAR PANEL 3-1

3.3 INSTALLATION AND CONNECTION TO HOST PC 3-4

CHAPTER 4: PRINCIPLES OF OPERATION .................................................................................4-1

4.1 OVERVIEW 4-1

4.2 SIMCHAN INTERFACE 4-2

4.2.1 Controlling the GSS6100 ................................................................................4-3

4.2.2 Help................................................................................................................4-3

4.2.3 Status bar .......................................................................................................4-3

CHAPTER 5: GSS6100 OPERATING DETAILS ..............................................................................5-1

5.1 SIMCHAN TOOLBAR 5-2

5.1.1 ARM the GSS6100 .........................................................................................5-2

5.1.2 RUN the GSS6100 .........................................................................................5-3

5.1.3 HALT the GSS6100........................................................................................ 5-3

5.2 SIMCHAN MAIN AREA 5-4

5.2.1 Pseudo Range Velocity ..................................................................................5-5

5.2.2 Velocity profiles ..............................................................................................5-6

5.2.3 RF Power .....................................................................................................5-11

5.2.4 Simulation Time............................................................................................ 5-12

5.2.5 Nav Data Message.......................................................................................5-13

5.2.6 PRN.............................................................................................................. 5-14

5.2.7 SBAS Message Rate.................................................................................... 5-16

5.2.8 Pseudo Range.............................................................................................. 5-16

5.2.9 Time into Run ...............................................................................................5-17

5.2.10 Prompts, Warnings and Errors......................................................................5-17

5.3 NAVIGATION DATA TEMPLATE 5-18

5.4 AUTOGO 5-20

5.4.1 Limitations of AutoGO...................................................................................5-21

5.5 HARDWARE OPTIONS AND SETTINGS 5-22

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5.6 SYNCHRONISATION 5-26

5.6.1 1PPS IN........................................................................................................ 5-27

5.6.2 TRIG IN – Immediate Mode..........................................................................5-27

5.6.3 TRIG IN – Delayed Mode..............................................................................5-28

CHAPTER 6: REMOTE INTERFACE ...............................................................................................6-1

6.1 INTERFACE TYPES 6-1

6.1.1 GPIB...............................................................................................................6-1

6.1.2 RS232.............................................................................................................6-1

6.2 COMMAND SET 6-2

6.2.1 Notes on the syntax definition.........................................................................6-2

6.2.2 *IDN?.............................................................................................................. 6-3

6.2.3 ARMS .............................................................................................................6-3

6.2.4 BITE................................................................................................................6-4

6.2.5 COSW ............................................................................................................6-4

6.2.6 EREF..............................................................................................................6-5

6.2.7 EREF ?...........................................................................................................6-5

6.2.8 GPIB...............................................................................................................6-5

6.2.9 HALT ..............................................................................................................6-6

6.2.10 IDEN...............................................................................................................6-6

6.2.11 IPRG...............................................................................................................6-6

6.2.12 LEVL............................................................................................................... 6-7

6.2.13 LEVL ?............................................................................................................ 6-7

6.2.14 MODE.............................................................................................................6-8

6.2.15 MODE ?..........................................................................................................6-8

6.2.16 NDSW.............................................................................................................6-9

6.2.17 NMOD.............................................................................................................6-9

6.2.18 NSAV............................................................................................................ 6-12

6.2.19 NSAV ?......................................................................................................... 6-13

6.2.20 NSEL ............................................................................................................6-13

6.2.21 PFIL.............................................................................................................. 6-14

6.2.22 PROF............................................................................................................6-14

6.2.23 PROS ...........................................................................................................6-15

6.2.24 PRTY............................................................................................................6-15

6.2.25 RSET............................................................................................................6-16

6.2.26 RUNS ...........................................................................................................6-16

6.2.27 SERR............................................................................................................6-17

6.2.28 G2D ..............................................................................................................6-17

6.2.29 SIGT .............................................................................................................6-18

6.2.30 SNUM ?........................................................................................................6-18

6.2.31 STAT ............................................................................................................6-18

6.2.32 SVID .............................................................................................................6-19

6.2.33 TIOP .............................................................................................................6-19

6.2.34 TIOP ? ..........................................................................................................6-20

6.2.35 TRIG............................................................................................................. 6-20

6.2.36 VCTY............................................................................................................6-21

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6.2.37 WEEK........................................................................................................... 6-21

6.2.38 WRTE........................................................................................................... 6-22

6.2.39 ZCNT............................................................................................................ 6-22

6.3 COMMAND AVAILABILITY BY MODE 6-22

6.4 SERIAL POLL – STATUS BITS 6-24

6.5 EXAMPLE COMMAND SEQUENCES 6-24

6.5.1 Example GPS operations..............................................................................6-24

6.5.2 Example with external trigger........................................................................6-26

6.5.3 Example with external signals.......................................................................6-27

CHAPTER 7: CALIBRATION .............................................................................................................7-1

7.1.1 Reference frequency calibration .....................................................................7-1

7.1.2 Power level calibration.................................................................................... 7-2

APPENDIX A: INSTALLING SIMCHAN .........................................................................................A-1

A.1 INSTALL SIMCHAN A-1 A.2 REMOVING SIMCHAN A-3 A.3 FIRST USE A-4

APPENDIX B: UPDATING FIRMWARE ......................................................................................... B-1

APPENDIX C: CONNECTING A GPS RECEIVER ........................................................................C-1

APPENDIX D: SIGNAL GENERATOR CONNECTIVITY............................................................D-1

APPENDIX E: BITE RESPONSE MESSAGE .................................................................................. E-1

APPENDIX F: STANDARD GPS NAVIGATION MESSAGE........................................................ F-1

F.1 INTRODUCTION F-1

F.1.1 Telemetry (TLM) Word – All Subrames...........................................................F-2

F.1.2 Handover Word (HOW) – All Subframes.........................................................F-2

F.1.3 Subframes 1 through 3 ...................................................................................F-3

F.1.4 Subframes 4 and 5 .......................................................................................F-10

F.1.5 Page ID’s 1 through 32................................................................................. F-11

F.1.6 Page ID 51....................................................................................................F-14

F.1.7 Page ID’s 52 Through 54..............................................................................F-18

F.1.8 Page ID 55....................................................................................................F-20

F.1.9 Page ID 56....................................................................................................F-22

F.1.10 Page ID 57....................................................................................................F-24

F.1.11 Page ID’s 58 Through 62..............................................................................F-26

F.1.12 Page ID 63....................................................................................................F-28

APPENDIX G: USER DEFINABLE NAVIGATION DATA ...........................................................G-1

G.1 INTRODUCTION G-1 G.2 FILE FORMAT G-1

G.2.1 General.......................................................................................................... G-1

G.2.2 Data Fields .................................................................................................... G-2

APPENDIX H: SBAS CORRECTION DATA FILES .......................................................................H-1

H.1 CREATING AND EDITING A SBAS CORRECTION DATA FILE H-1

H.1.1 Example ........................................................................................................ H-2

H.1.2 Default *.WAS file, WAAS_DEF.WAS............................................................ H-2

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H.1.3 Possible *.WAS data errors.......................................................................... H-23

APPENDIX I: PRODUCT SAFETY AND COMPLIANCE ..............................................................I-1

I.1 SAFETY NOTICE I-1 I.2 EMC AND SAFETY COMPLIANCE I-2

APPENDIX J: SPECIAL NAV DATA TEMPLATE..........................................................................J-1

APPENDIX K: CONTACTING SPIRENT CUSTOMER SUPPORT ................................................ I

INDEX

LIST OF FIGURES

LIST OF TABLES

VII

VIII

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Chapter 1: General

1.1 Record of issue

Issue Date Description

1-00 Oct 2005 First issue

2-00

2-01

Nov 2006

July 2007

Updated style to match Spirent documentation Changed screenshots for SimCHAN v1.05 and included new text as appropriate. Changes to improve readability. Added Special Nav Data template to Appendix.

Bugz

2163: Clarified calibration procedure

2325: New folder locations

2868: Changes to velocity profile sections and added info on USER profile

Changed company name Changed contact details Usability Placed Fig 3-2 on Landscape page to allow resize for improved readability

Bugz:

3122: Added pin-out table for 1PPS IN / OUT. 3238: Added NMOD command and details on special NAV templates 3586: Updated contact details.

GSS6100 and SimCHAN user manual © Spirent Communications Plc 2005 - 2007

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1.2 Referenced documents

a) ICD-GPS-200 - Document defining the GPS system space and

user segments.

b) STANAG 4294 The NATO equivalent of the above document.

c) NMEA 0183 - Document defining a standard set of navigational

messages supported by many GPS receivers.

d) RTCM-SC104 - Document defining a set of differential

correction messages accepted by many GPS receivers.

e) RTCA-DO229 and 229A - Minimum operational performance

standards for Global Positioning System/Wide Area Augmentation System Airborne Equipment

f) ICD-GPS-204 - Standard Receiver Performance Tests,

g) MS3037 - GSS6100 Product Specification

1.3 Deliverables

a) GSS6100 GPS/SBAS Signal Generator

b) User Manual

c) SimCHAN software on CD-ROM

d) USB cable

e) Power cables (Country specific)

f) Spirent mouse mat

1.4 Copyright notices

IBM PC/AT are registered trademarks of International Business Machines Corporation.

Microsoft and Windows are either trademarks or registered trademarks of Microsoft Corporation.

InstallShield is a registered trademark of InstallShield Software Corporation.

All other company/product names referenced herein are trademarks and/or service marks or registered trademarks and/or service marks of their respective holders.

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1.5 Acronyms and abbreviations

1CPS One Character Per Second

1PPS One Pulse Per Second

<CR><LF> Carriage Return and Line Feed characters

AGP Advanced Graphics Port – a type of graphics card

socket found in a PC

ASCII Standard character set used for serial

communications

CD-ROM Term for a Compact Disk when used as a PC

storage medium

DLL Dynamically Linked Library – Microsoft promoted

mechanism for sharing common code between applications.

EOI End or Identify

GPIB General Purpose Interface Board – term for the

National Instruments IEEE-488 bus interface cards.

GUI Graphical User Interface

IEEE Institute of Electrical and Electronic Engineers –

standards body for many widely used interfaces

I/O Input Output

IP Internet Protocol – generically the set of standards

that define the Internet

IRQ Interrupt Request Level – a resource option for PC

interface devices, normally set automatically by devices that meet ‘Plug and Play’ standards

PCI A standard type of interface board socket found in

PCs

PCMCIA A standard interface commonly supplied for

portable computers. Also known as PC Card it is Hot Pluggable enabling devices to be added/removed as needed.

PPM Parts Per Million

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PRN Pseudo Random Number

TCP/IP Transmission Control Protocol – the main interface

standard used for reliable connection mode communications via the Internet

Toa Time of Application

UDP/IP User Datagram Protocol – interface standard for

connection less communications via the Internet

USB Universal Serial Bus – Hot pluggable interface for

PC peripheral devices

VMS Acronym for the Operating System used with DEC

Alpha Workstations.

XML eXtensible Markup Language – a standard syntax

and semantics for passing information between computers as a text based vendor independent file.

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1.5.1 Document conventions

1.5.1.1 Software

The user interface, shown in Figure 1-1, uses standard Windows XP commands (including keystroke alternatives to using a mouse) and controls.

Figure 1-1 SimCHAN interface

This document refers to:

a) Buttons, such as Clear, with Bold text.

b) Filenames, such as GSS6100.ini, with Bold italic text.

c) Text boxes, such as Velocity (m/sec) with Bold text.

You enter data values by typing the value in the text box, which is referred to by its name, for example Pseudo Range Velocity – Velocity (m/sec). Where necessary, this document refers to the area name (Pseudo Range Velocity) to avoid ambiguity. Alternatively, some text boxes have Up/Down arrows. Click on these arrows, as required, to select a value from the presented values.

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Other multiple choice selections use drop-down lists, such as Nav Data Message – Message Type. Click on the Down arrow to the right of the text

to display the drop-down list. Select the item you want.

Some parameters, such as PRN-PRN Code On have two states (for example, on or off). Click in the box to select (turn on) PRN-PRN Code

On. A tick mark appears in the box. De-select (turn off) PRN-PRN Code On, by clicking in the box again. The tick mark disappears.

Some parameters, such as Velocity Profile ON, are disabled and use grey, rather than black, text and a grey rather than white background to the box.

1.5.1.2 Hardware

This document refers to:

a) The GSS6100 as a signal generator.

b) “Operating” the GSS6100 to produce an RF signal.

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Chapter 2: Introduction

Thank you for purchasing a GSS6100 GPS/SBAS signal generator from Spirent, world leaders in the field of Satellite Navigation Systems Simulation.

The GSS6100 is a precision, stand-alone, single-channel, L1 C/A code GPS signal generator that uses the SimCHAN control software. Typically the GSS6100 is used to evaluate GPS/SBAS receivers and applications for the GSS6100 include design verification, production test, comparative evaluation, statistical data-generation through extended and repeated tests, and incoming product test.

The Global Positioning System (GPS) is based upon a constellation of earthorbiting satellites supporting world-wide precise positioning, navigation and timing for both terrestrial and earth orbiting vehicles.

Satellite Based Augmentation Systems (SBAS) provide enhanced accuracy, availability and integrity for GPS users in the civil community via one or more geosynchronous satellites. The Wide Area Augmentation System (WAAS) is a system planned for the continental United States. Similar compatible systems are also planned for Europe (EGNOS) and the Far East (MSAS).

The GSS6100 fully supports both standard GPS and SBAS.

2.1 SimCHAN or remote operation

You can control the GSS6100 in one of two ways:

SimCHAN - a user-friendly software package that communicates with the GSS6100 using the USB bus.

Remote Control - in this mode, you use Spirent’s proprietary remote command set to the signal generator. You can apply the remote command set using the IEEE or RS232 interfaces.

Because the remote command set is closely aligned with Spirent’s previous single channel products (the GSS4100 and GSS4700), porting any existing remote control applications to the GSS6100 is a straightforward exercise.

Note: Both modes of operation offer identical control capability.

GSS6100 and SimCHAN user manual © Spirent Communications Plc 2005 - 2007

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Chapter 3: Hardware overview and installation

This section gives an overview of the indicators and connectors present on a GSS6100; and how to connect it to the host PC.

Spirent Specification, reference

g), gives full details of the connectivity and

signals produced by the GSS6100, together with environmental information.

3.1 Front panel

Figure 3-1 shows the GSS6100 front panel. Table 3-1describes the front panel indicators and connector.

Figure 3-1 GSS6100 front panel

POW ER HEAL T H

GSS6 1 00 GPS/ SBA S Si gn al G en er a t o r

OUTPUT

ACTIVE

Table 3-1 Front panel indicators and connector

Indicator Type Description

POWER LED ON when ac power connected and internal power

supply operational.

HEALTH LED Normally ON.

Flashes at 1 Hz when an error detected. Flashes at 4Hz while acquiring external reference lock.

spi re nt com .co m

ACTIVE LED ON when the signal generator is operating.

Flashes when awaiting an external trigger signal on rear panel TRIG IN

Connector Type Description

Primary RF Output

GSS6100 and SimCHAN user manual © Spirent Communications Plc 2005 - 2007

Co-axial type N

Provides a composite GPS/SBAS signal

Hardware overview and installation

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3.2 REAR PANEL

Figure 3-2 GSS6100 rear panel

Made in U.K.

MODEL: GSS6100

S/N: XXXX

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Table 3-2 Rear panel connectors

Connector Type Description

MON/CAL Output SMA female Provides a high-level version of the front panel RF output.

AUX OUTPUT 25-way D type See Table 3-3

TRIG IN BNC Allows an external trigger signal to start a simulation.

TTL level compatible:

-0.5 V < Low < +0.8 V +2.0 V < High < +5.5 V 50  input impedance Section

5.6 shows timing details.

EXT REF IN BNC Locks the GSS6100 to an external frequency reference.

10 MHz OUT BNC Internal OCXO reference output.

HOST (USB) USB downstream connector Control and data connection to the host PC.

RS232 9-way D type Control and data connection to a remote terminal.

HOST (IEEE-488) IEEE-488 Control and data connection to a remote terminal.

Power in/switch/fuse IEC AC power in, see reference g)

Reference g) gives further details of the rear panel connectors.

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Table 3-3 1 PPS IN / OUT 25 way connector pin-out

Pin Function

11PPSIN1* 2 1PPS OUT2* 3 Reserved 4 Reserved 5 Reserved 6 Reserved 7 Reserved 8 C/A CLOCK*

9 CODE 1PPS* 10 C/A EPOCH* 11

AV DATA* 12 C/A CODE* 13

ot connecte 14 Ground for 1PPS IN 15 Ground for 1PPS OUT 16

ot connecte 17 Ground 18 Ground 19 20

ot connecte

ot connecte 21 Ground for C/A CLOCK 22 Ground for CODE 1PPS 23 Ground for C/A EPOCH 24 Ground for NAV DATA 25 Ground for C/A CODE

Note:

i) Input signals marked * are 50 ohm terminated.

ii) Output signals marked * are 50 ohm drive capable.

1 In combination with the External Reference input, 1PPS IN can be used to synchronise the simulator to an external system, see

Section 5.6, TTL level compatible.

2 TTL level compatible, nominal pulse width 100ms

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3.3 Installation and connection to host PC

Note: Before connecting the GSS6100 to the PC, you must install the SimCHAN software.

Note: Before running SimCHAN the Power and Health LEDs on the front panel of the GSS6100 must be continuously illuminated.

Using your chosen interface, connect the GSS6100 to the controlling host PC. The interfaces available are either USB for SimCHAN Software operation or RS232 / IEEE.488 cable for remote control.

Note: Spirent recommends that users new to the GSS6100 use SimCHAN before moving onto remote operation. Using SimCHAN for set-up, control and adjustment of the signal generator is more instructive.

Apply ac power to the GSS6100 and switch it on.

Note: The power input to the GSS6100 is auto sensing for 100-120V or 220240V operation.

After a brief power-up sequence, the POWER and HEALTH LEDs on the GSS6100front panel illuminate continuously to show correct operation.

The GSS6100 is now ready for remote control operation.

Alternatively, you can start SimCHAN by double-clicking the SimCHAN icon on the desktop or by using the shortcut in the Windows Start menu.

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Chapter 4: Principles of operation

4.1 Overview

The GSS6100 requires instructions to configure and commence operating the signal generator. The SimCHAN software provides these instructions using the USB bus; or by command sequences transmitted to the GSS6100 using the IEEE-488 bus or an RS232 port.

Regardless of which method of control you have selected, the GSS6100 has three software states, Halt, Arm and Run.

In the Halt state, you configure the next signal generator operation run by selecting parameters such as the satellite PRN number, navigation message parameters (TOW, Week Number), initial power/velocity and any hardware conditions such as external reference lock or external trigger control.

Once you have set these attributes, the GSS6100 must be set into the Arm state.

The Arm state is an interim step prior to setting the GSS6100 into the Run state. The Arm state configures the GSS6100 and allows you to make any final adjustments to certain parameter types.

Once in the Run state, the GSS6100 is operational and all requested characteristics are present on the RF output connector.

While in the Run state, you can adjust and control many parameters to suit the operation profile you need. At the end of the run, the GSS6100 is set into the Halt state and the process repeated, as required.

Chapter 5: describes each of the available operating and hardware control parameters. For clarity, these descriptions use the SimCHAN graphical interface and include a cross-reference to all applicable remote control commands.

Chapter 6: gives a full listing of the remote control commands.

GSS6100 and SimCHAN user manual © Spirent Communications Plc 2005 - 2007

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4.2 SimCHAN interface

SimCHAN lets you set and adjust in real time, the operating parameters of the GSS6100. It also displays messages.

SimCHAN has three main areas, see

a) The menu and tool bar.

b) The main area.

c) The status bar.

Figure 4-1 SimCHAN interface

Figure 4-1:

4-2 Principles of operation

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4.2.1 Controlling the GSS6100

You can set the Arm, Run and Halt actions using:

a) The Run menu.

b) The SimCHAN Toolbar buttons.

c) The Hot keys: Ctrl+A (Arm), Ctrl+R (Run) and

Ctrl+H (Halt).

Note: Selection using keystrokes to open Menu items and Hot keys are only effective when SimCHAN is active, that is, the title bar of SimCHAN is highlighted. Alt+F6 toggles SimCHAN to the active state.

4.2.2 Help

The Help menu lets you select HTML format versions of the GSS4100 user manual and the GSS6100 user manual. You can also press F1 to open the Help menu.

Click on About to see details on the GSS6100 signal generator connected to the PC and the version of SimCHAN.

4.2.3 Status bar

The Status Bar has fields that show:

a) The state of SimCHAN

b) The state of operation of the signal generator,

c) Internal/External Frequency Reference signal,

d) Presence of a working USB connection.

GSS6100 and SimCHAN user manual © Spirent Communications Plc 2005 - 2007

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Chapter 5: GSS6100 operating details

All parameter settings you apply to the GSS6100 are written to a file. You can save this parameter file using the File menu. The default parameter file extension is .gss.

A parameter file can be loaded before SimCHAN runs. Using a parameter file lets you easily and quickly run the GSS6100 in a known state.

The New menu resets all SimCHAN parameters to their default states.

You control the GSS6100 using the tool bar.

Table 5-1 details the section numbers for each parameter on the SimCHAN main dialog box.

Table 5-1 Parameter section references

Parameter Section

Pseudo Range Velocity 5.2.1

Velocity profile 5.2.2

RF Power 5.2.3

Simulation Time 5.2.4

Nav Data Message 5.2.5

PRN 5.2.6

SBAS Message Rate 5.2.7

Pseudo Range 5.2.8

Time into Run 5.2.9

GSS6100 and SimCHAN user manual © Spirent Communications Plc 2005 - 2007

GSS6100 operating details

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5.1 SimCHAN toolbar

The toolbar, see

Figure 5-1, is the primary method of controlling the

GSS6100.

Figure 5-1 Toolbar

The toolbar also gives access to the file functions:

New Close any open parameters file

Open The Windows Open file dialog box.

Save Saves the current parameters to a file or

Resets the parameters.

prompts for a new file name.

The toolbar also gives the basic control functions of ARM, RUN and HALT.

5.1.1 ARM the GSS6100

[Remote Command: ARMS see section 6.2.3]

Figure 5-2 ARM button

Click ARM to load the selected parameters to the GSS6100 and to prepare for a run.

The Status bar shows ‘Ready to Run’ when the arming sequence is complete.

5-2 GSS6100 operating details

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5.1.2 RUN the GSS6100

[Remote Command: RUNS see section 6.2.26]

Figure 5-3 START button

Clicking START releases the GSS6100 to begin the prepared operation. Independent of mode (see section

5.5.1.1), you must use this button to start

the GSS6100.

The front panel ‘Active’ LED illuminates

after clicking START.

To return to the idle state without running the GSS6100, click HALT.

5.1.3 HALT the GSS6100

[Remote Command: HALT see section 6.2.9]

Figure 5-4 HALT button

Click HALT to abort the operation in progress or terminate the Ready to Run state.

After you click HALT, SimCHAN and the GSS6100 return to the Idle state.

You can HALT the operation to change parameters.

The time at which the RUN command is actioned in the hardware is dependent upon the selected Ext Trigger mode. The simulation start time will coincide with the next rising edge of 1PPS OUT, if Ext Trigger is ‘disabled’ or in ‘delayed’ mode, or immediately if Trigger mode ‘immediate’ has been selected.

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5.2 SimCHAN main area

Use the main area of the SimCHAN interface, see operating parameters.

Figure 5-5 SimCHAN interface

Figure 5-5, to enter the

5-4 GSS6100 operating details

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5.2.1 Pseudo Range Velocity

[Remote Command: see VCTY section 6.2.36]

This is the rate of change of the Satellite’s simulated Pseudo Range in metres per second. The allowed values range from -15000.00 to +15000.00 at a resolution of 0.01 meters per second.

Use the Up and Down arrows to the right of the Velocity text box to step the velocity from –15000.00 through to +15000.00 m/s. You can set the step size by typing a suitable value in the Increment text box.

Figure 5-6 Pseudo-range velocity area

Note: Each time you click on the Up or Down arrow to the right of the Velocity Increment text box, the value shown in the Velocity Increment text box will be added, or subtracted, to the Pseudo Range Velocity

5.2.1.1 Velocity increm ent

The Up and Down buttons to the right of the Velocity text box increment and decrement the Pseudo Range Velocity by a value defined in the Velocity Increment text box.

The allowed values of Velocity Increment range from 0.01 to 5000.00 metres per second.

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5.2.2 Velocity profiles

[Remote Command: PROF see section 6.2.22]

Select Velocity Profile ON to use a velocity profile. After selecting Velocity Profile ON you must also select a Profile Data File, see section

5.2.2.2.

This option is only available when the GSS6100 is running. The velocity profile superimposes a cyclic sequence of changes to the selected Pseudo Range Velocity.

The velocity profile remains applied until you de-select Velocity Profile ON.

You can use Velocity Profiles with the remote command: section

5.2.2.1 More on velocity profiles

6.2.23.

PROS, see

Table 5-2 describes the elements used in velocity profiles. Figure 5-7 shows these elements.

A velocity profile takes the form of a series of step jerk periods of equal amplitude and period. These jerk periods then translate into acceleration, velocity and finally range profiles.

The velocities generated by the profile are in addition to any fixed velocity specified. The maximum achievable velocity is +/-15000 m/s. Velocities exceeding these limits will be clipped to the appropriate maximum velocity.

Table 5-2 Elements used in velocity profiles

Parameter

Reference in

Figure 5-7

Unit

Maximum Jerk A m/s3

Jerk Period B s

Constant acceleration period

C s

Constant velocity period D s

Maximum acceleration E m/s2

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Figure 5-7 Velocity Profile Elements

Note: The velocity profile shown in

Figure 5-7 shows either constant or linearly changing velocity. During the jerk period (which is a period of linearly increasing/decreasing acceleration) the velocity changes nonlinearly. The GSS6100 fully models these effects.

Reference

f) documents the profile. It comprises the following sequence:

Constant Initial Velocity Period (D)

Positive Jerk Period (B = Max Acceleration/ Maximum Jerk (A))

Constant Acceleration Period (C)

Negative Jerk Period (as ii)

Constant Positive Velocity Period (D)

Negative Jerk Period (as ii)

Constant Deceleration period (C)

Positive Jerk Period (as ii)

The profile then repeats but with the Jerk sign reversed, producing negative velocities.

Finally, the entire profile repeats from the start.

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5.2.2.2 Profile Data File

[Remote Command: PFIL see section 6.2.21]

Figure 5-8 Profile Data File

Figure 5-8 shows the Profile Data Files available. The GSS6100 firmware incorporates eight standard profiles PROF1 through PROF8, corresponding to the profiles defined in reference

f). Table 5-3 details these profiles.

Table 5-3 Stored values for PROF1 to PROF8

Profile

Jerk

amplitude,

m/s

Maximum

acceleration,

m/s

Period of

constant

acceleration, s

Period of

constant

velocity, s

1 20.0 6.0 1.1 1.1

2 20.0 10.0 2.0 2.0

3 100.0 10.0 4.9 4.9

4 10.0 10.0 0.5 0.5

5 20.0 6.0 3.8 3.8

6 40.0 20.0 7.0 7.0

7 100.0 90.0 22.9 22.9

8 17.5 7.0 4.6 4.6

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You can create a User Velocity Profile by first selecting Profile Data File – USER. This enables the text boxes in the User Velocity Profile area.

Table 5-4 gives the ranges for the User Velocity Profile parameters.

Table 5-4 Parameters for User Velocity Profile

User Velocity Profile Parameter Range

Jerk Amplitude

Max Acceleration

-100 to 100 m/s

Note: Zero Jerk is not allowed.

-100 to 100 m/s

Period of Const Accel

Period of Const Velocity

0 to 540 s

Note: Jerk application period = (max acceleration / 0.01 s)

The jerk application period must be divisible by the interrupt step size, which is 10ms.

To ensure this is always true, you must manually inspect and modify the entered jerk.

Note: SimCHAN does not carry out this computation. You must complete this computation and enter the appropriate data.

For example:

a) You require a jerk value of 20 m/s

15.5 m/s

. This produces a jerk period of 0.775 seconds.

and use an acceleration of

b) This jerk period is not divisible by 0.01 s (10 ms).

c) First, round the jerk period down to 0.770 seconds.

d) With your acceleration of 15.5 m/s

results in a jerk of 20.1298 m/s

, a jerk period of 0.770 s

e) Now round the jerk period up to 0.780 seconds

f) With your acceleration of 15.5 m/s

results in a jerk of 19.8718 m/s

g) Choose the jerk value nearest your required 20 m/s

19.8718 m/s

, a jerk period of 0.780 s

, that is,

h) Use this jerk in the User Velocity Profile you create.

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To save the USER profile for re-use select “Save as” from the SimCHAN File menu and save to a file of your choice. To recall the settings select “Open…” from the File menu and recall the saved file. (Note that this actually saves ALL the current application settings.)

5.2.2.3 Carrier Doppler Offset

[Remote Command: VCTY section 6.2.36]

Figure 5-9 Setting Carrier Doppler Offset

Carrier Doppler Offset can be used to simulate Ionospheric delay type

effects by applying a fixed Doppler velocity offset to the current carrier Doppler velocity. The code Doppler velocity remains unchanged.

The Carrier Doppler Offset value has a range from –1000.00 through +1000.00 to a resolution of 0.01 m/s.

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5.2.3 RF Power

[Remote Command: LEVL see section 6.2.12]

Figure 5-10 Setting RF Power Level Offset

The RF Power Level Offset may be varied to + or – 20.0 dB of the base level to a resolution of 0.1 dB.

Note: A value outside the allowed range truncates to the limit value.

5.2.3.1 RF Power Level Offset

The Up and Down buttons to the right of the RF Power Level Offset text box increment and decrement the RF Power Level Offset by a value defined by the Level Increment.

You can also click on the slider and drag it to change the RF Power Level Offset. The slider forces the RF Power Level Offset to a multiple of the value selected in Level Increment.

To avoid discontinuities at the range limits when using a user-defined Level Increment, the nearest pre-defined Level Increment value is used, rather than the user’s value.

5.2.3.2 RF Power - Level Increment

You can set any value, including values greater than the RF Power Level range of 40.0 dB.

Alternatively a value may be selected from the range of pre-defined values by selecting the Up/Down arrow buttons next to the control.

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5.2.4 Simulation Time

Here, simulation refers to operation of the GSS6100.

5.2.4.1 GPS week number

[Remote Command: WEEK see section 6.2.37]

Figure 5-11 Setting Simulation Time

GPS Week Number is closely linked with the start of week since it defines the GPS week for the simulation. GPS week zero is defined as starting at 00:00 hours, Sunday 6

January 1980.

For example, the default value of 800 corresponds to the week starting Sunday, 7

May 1995. GPS week numbers greater than 1023 will be

truncated internally modulo 1024, i.e. Week 1025 is treated as week 1.

The week number may be entered as a value between 0 through 9999.

5.2.4.2 Time of Week

[Remote Command: ZCNT see section 6.2.39]

This value is the time into the week expressed in GPS Epochs that will be applied at the start of the operation. When the GSS6100 is running, this value increments to show the current Time of Week.

The allowed values range from 0 through 403196 in steps of 4 GPS Epochs.

1 GPS Epoch = 1.5 Seconds

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5.2.5 Nav Data Message

[Remote Command: NDSW see section 6.2.16]

You can prevent generation of the Nav Data Message by de-selecting

Navigation Message On.

Figure 5-12 Nav Data Message dialog box

5.2.5.1 Message Type

[Remote Command:, SIGT see section 6.2.29]

Select either GPS or SBAS in Nav Data Message – Message Type.

With the GPS setting, the RF signal from a GPS type satellite is produced and the control options appropriate to GPS are activated.

With the SBAS setting, the RF signal from an SBAS type satellite is produced and the control options appropriate to SBAS are activated.

Note: You must select SBAS to enable SBAS Message Rate.

5.2.5.2 Message Parity

[Remote Command: PRTY see section 6.2.24]

Parity errors may be produced on the Nav Data Message by de-selecting Message Parity. This inverts each parity bit, thus invalidating it.

Note: The data message is buffered in hardware. Changing the parity status while the GSS6100is running results in a delay before the change is reflected in the RF output. Spirent recommend you set-up this feature while SimCHAN is idle and the GSS6100 is not operating.

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5.2.5.3 Message File Template

[Remote Command: NSEL see section 6.2.20]

The GSS6100 can store up to 8 Message File Templates in its Flash memory. You can fill these eight memory “slots” with four GPS Navigation Message Templates and four SBAS Correction Data message Templates. Selecting a GPS constellation selects Templates for GPS Navigation Messages; otherwise SBAS Correction Message Templates are selected.

For either GPS or SBAS, a Message File Template number in the range 0 to 3 identifies the appropriate Template. The Message File Template number shown will be the active selection for the GSS6100, it is used to generate the Navigation/Correction message component of the RF signal.

5.2.6 PRN

The PRN (Pseudo Random Noise) Number defines the C/A code for the satellite being produced and equates to the SV ID (Satellite Vehicle Identity).

5.2.6.1 PRN Number

[Remote Command: SVID see section 6.2.32 & G2D see section

6.2.28]

Figure 5-13 PRN dialog box

The PRN value is constrained to the range 1 to 37 for GPS type satellites and 120 to 138 for SBAS satellites.

SimCHAN offers a default value of 1 for the GPS constellation and 120 for an SBAS constellation.

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5.2.6.2 PRN Code On

[Remote Command: COSW see section 6.2.5]

Disable PRN code generation by de-selecting PRN Code On.

The GSS6100 is capable of generating any one of the 1023 possible random sequences associated with the GPS C/A encoder. Each sequence or code is determined by the start conditions of the G1 and G2 encoders.

The G1 encoder is hardwired to start in the “all ones” state, the G2 encoder, can start in any state except all zeros.

The G2 start conditions can be described by a ‘G2 delay’, which can take values between 0 and 1022.

Conventionally, several of the 1023 codes (mainly codes with good orthogonal properties, such as low cross correlation) have been assigned PRN numbers, see

Table 5-5.

Note: SimCHAN constrains the PRN assignment to the values allocated for GPS or SBAS satellites.

Table 5-5 PRN assignments

PRN No. Assignment

1 - 37 GPS

38 - 61 GLONASS

62 - 119 Future GLONASS

120 - 140 GEO/SBAS

141 - 210 Future GNSS/GEO/SBAS/Pseudolites

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5.2.7 SBAS Message Rate

[Remote Command: WRTE see section 6.2.38]

Figure 5-14 SBAS dialog box

You must select Nav Data Message – Message Type - SBAS to enable the SBAS Message Rate.

The Message Rate controls the rate at which the Correction message is transmitted during an SBAS type operation.

You can choose one of four rates from the drop-down list: 50, 100, 125 and 250 data bits per second. 250 bps is the default setting, which is equivalent to 500 symbols per second when forward error corrected.

Note: The Message Transmission rate for GPS satellites is fixed at 50 bps.

5.2.8 Pseudo Range

[Remote Command: IPRG see section 6.2.11]

Note: Pseudo Range may only be set while the GSS6100 is idle.

Pseudo Range simulates the distance between the receiver and the satellite at the start of the run. This ranging effect is produced by delaying the start of the PRN and data message signals to simulate the desired pseudo range. The time delay is relative to rising edge of the 1PPS OUT signal (Ext Trigger mode ‘disabled’ or ‘delayed’ or relative to the External Trigger pulse itself if Trigger mode ‘immediate’ has been selected, see section

5.5.1.1).

Figure 5-15 Pseudo Range dialog box

Pseudo Range can take any value between 0 and 99999999 metres

(equivalent to 333 ms time delay) and has a resolution of 1 metre.

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5.2.9 Time into Run

This shows the elapsed time of the operation, in seconds.

5.2.10 Prompts, Warnings and Errors

[Remote Command: BITE see section 6.2.4]

Figure 5-16 Warning and prompts log window

SimCHAN will display single line text messages describing events that occur during execution of the program in the text box towards the bottom of the SimCHAN window.

The messages are stored in time sequence with the latest message displayed. You can view the record of events by clicking the down arrow on the righthand side of the text box to open the list and then scrolling to view the messages.

You can clear all messages by clicking Clear.

Note: SimCHAN automatically removes old messages and it is not normally necessary to clear old messages.

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5.3 Navigation Data Template

The GPS Navigation message and the Correction Data message in SBAS mode are generated from templates pre-loaded in the GSS6100 flash memory. The templates provided for each of these modes should be sufficient for most test purposes. Spirent also provides these templates as ASCII files.

The GPS Navigation Message carries date and time information that increments at the 6 second GPS Epoch rate. This is automatically inserted by the GSS6100 to match the operation time. The parity field is computed dynamically by the GSS6100, but data other than Epoch time remains fixed.

To allow you to meet specific testing requirements, you can load a further 3 templates of each type, using either the NSAV command or using the SimCHAN graphical interface and the USB bus.

Templates are plain text files and may be examined and altered by any text editor such as Windows Notepad.

Save modified templates to the SimCHAN program folder, typically

C:\Documents and Settings\All Users\Application Data\Spirent Communications\SimCHAN.

Note: GPS Navigation message templates must use the NAV extension and

an SBAS Correction data message must use the WAS extension.

To load a specific template, use the Options-Load Navigation Message Template dialog box, see

Figure 5-17.

Figure 5-17 Load Navigation Template

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a) Select the template type, either GPS or SBAS.

b) Select a template from the Template File Available drop-down

list.

c) Use Template Slot ID to select the ID number of the GSS6100

flash memory location that will hold the template. There are four locations numbered 0 to 3.

Note: ID number 1 is the default to prevent overwriting the GSS supplied template pre-loaded in template number 0.

d) Click Load to load and use the selected template.

For a full description of default message parameters and how to define user *.NAV and *.WAS files see

Appendix F: and Appendix G:.

Appendix J: gives details of a Nav Data template that produces a programmable Nav Data message. You can only use this template with firmware version 1.11 on.

Note: You must save all user-defined Nav Data files to the following folder:

C:\Documents and Setting\All Users\Application Data\Spirent Communications\SimCHAN\

Note: You must enter the full path and filename in the Load Navigation

Message Template screen, for example:

C:\Documents and Setting\All Users\Application Data\Spirent Communications\SimCHAN\filename.nav

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5.4 AutoGO

The GSS6100 has an alternative operating mode that causes it to commence running a stored scenario immediately it is powered on. No external command is required.

To enable AutoGO:

a) Start SimCHAN

b) Ensure the GSS6100 is connected,

c) Apply the desired initial settings,

d) Select Options - Set AutoGO

e) The settings are applied to the GSS6100.

f) Options - Set AutoGO will now show Disable AutoGO

indicating the GSS6100 is set to run in the AutoGo mode.

g) When the GSS6100 is powered on, it will immediately

commence running using the stored settings.

If SimCHAN is started while the GSS6100 is operating in AutoGo mode, SimCHAN will display the initial settings stored in the GSS6100’s flash memory. The GSS6100 will continue to run with SimCHAN active but SimCHAN will not display the running state or update the scenario time displays to reflect the progress of the scenario.

To stop AutoGO and use SimCHAN:

a) Click the ARM button followed by the STOP button.

b) The GSS6100 will HALT.

Now you can use SimCHAN normally.

Note: When next powered on, the GSS6100 will start in AutoGO mode, unless you disable AutoGO.

To disable AutoGO:

a) Start SimCHAN

b) Ensure the GSS6100 is connected.

c) Select Options - Disable AutoGO.

d) The settings are deleted from the GSS6100 flash memory and

normal operating mode is enabled.

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5.4.1 Limitations of AutoGO

1. External Trigger cannot be utilised.

2. If an external reference frequency signal is applied, there will be

a period (after the GSS6100 starts running) when the RF signal is disturbed and out of specification. This state will continue until the GSS6100 locks to the reference signal. The HEALTH LED on the front panel will flash until the GSS6100 locks to the reference signal.

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5.5 Hardware options and settings

View the Hardware Options and Settings dialog box by clicking Options – Hardware Settings.

Figure 5-18 Hardware Options and Settings

The Hardware Options and Settings dialog box, see

Figure 5-18, displays the Serial Number of the connected GSS6100 unit and the Versions/Release numbers of the various Firmware elements loaded into the unit. The following sections describe the hardware related parameters that can be controlled and selected.

[Remote Command to check firmware version: *IDN? See 5.1.4]

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5.5.1.1 External T rigger

[Remote Command: TRIG see section 6.2.35]

If you want to start the GSS6100 from an external event, you must set the External Trigger mode.

Regardless of Trigger mode, you must click RUN to start operating the GSS6100

The External Trigger options are:

1) Disabled No external trigger is required to start the run. The run will start

when the next internal 1PPS event occurs (‘RUN’ 1PPS event). Operatting start time is coincident with the rising edge of the 1PPS OUT signal

2) Immediate In this mode the internal 1PPS signal is stopped and restarted

immediately on the rising edge of a signal applied to the External Trigger connector. The operation will start and 1PPS OUT will transition high approximately 600-700nsecs after the applied External Trigger signal.

3) Delayed In this mode the GSS6100 waits for the External Trigger signal

to be applied but will hold off commencing the operation until the next internal 1PPS event occurs (‘RUN’ 1PPS event). Operation start time is coincident with the rising edge of the 1PPS OUT signal

It should be noted that this is different to the STR4775 product where the External Trigger is applied whilst the Signal generator is in the ARMED state. With the GSS6100 the signal generator must be in the RUN state before for the Ext Trigger signal will be actioned.

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5.5.1.2 1PPS Out

[Remote Command: TIOP see section 6.2.33 & TIOP ? section

6.2.34]

1PPS Out is used to select the signal on the 1PPS rear panel connector. You can select from:

1PPS

Continuously outputs 1Hz pulses with the rising edge of each pulse coincident with the GPS 1-second epoch produced by the GSS6100

Gated

As 1PPS, but the signal is disabled before a run, the first rising edge coincides with operation time 0, start of run.

Rising

High

Low

5.5.1.3 IEEE Primary Address

A single rising edge occurs at operation time 0, start of run

Sets signal permanently high

Sets signal permanently low

[Remote Command: GPIB see section 6.2.8]

The GSS6100 is controlled using the IEEE-488 bus, using the IEEE primary address number (PAD) you select in the IEEE Primary Address text box.

The IEEE Primary Address can take values in the range 1 through 30.

5.5.1.4 Info Mask.

This is a debug facility and is disabled in normal use.

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5.5.1.5 Reference Fre quency

[Remote Command: EREF see section 6.2.6 & EREF ? see section

6.2.7]

The GSS6100 can detect the presence of an external frequency reference signal but cannot automatically determine the frequency. The GSS6100 will automatically lock to the external signal, but only achieves a fully stable lock when the External Frequency is correctly declared.

Select the frequency of the external frequency reference using the Reference Frequency – External Frequency drop-down nd click on the reference frequency you want to use. The supported external frequencies are 1, 5 and 10MHz.

The GSS6100 will automatically seek phase lock with the supplied signal.

The Locked / Unlocked symbols indicate when a stable phase lock occurs. Generally, it takes between 10 and 20 seconds to achieve phase lock.

The External Reference Phase lock is replicated on the Status Bar of the Main Display. This is grey when no Reference signal is being detected, Red when out of lock and Green when locked

Note: You cannot operate the GSS6100 while the reference frequency is unlocked. You cannot attempt to phase lock wile the GSS6100 is operating. If the reference frequency becomes unlocked during operation, an error will occur.

Note: Before attempting to phase lock to an external reference frequency, wait at least 15minutes after switch on to allow the GSS6100 10MHz OCXO to stabilise.

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5.6 Synchronisation

The GSS6100 signal generator incorporates input and output signal ports which can be used in various ways to synchronise time between the GSS6100 signal generator and the remainder of the system. This section describes how to use the 1PPS IN and/or TRIG IN inputs to achieve synchronisation.

The GSS6100 signal generator maintains time internally by means of a time counter, clocked by an internal 10MHz clock. Operations always start on a one-second rollover of this timer.

The timer may be synchronised to an external system before starting an operation by applying a rising edge to the 1PPS IN rear panel input

. Then operations may be started either by appropriate timing of the software run command (Trigger Mode: Disabled); or by selecting Delayed Trigger Mode and applying a rising edge to the TRIG IN input. Both cause the operation to start on the next one-second rollover of the timer.

Alternatively, you can select Immediate Trigger Mode, which forces the timer to a point just before the one second rollover and freezes it until a rising edge is detected on the TRIG IN input, the operation starts running after a short delay.

Note: the use of TRIG IN (Immediate Trigger Mode) together with 1PPS IN is inappropriate, as both would be attempting to control the timer. However, TRIG IN (Delayed Trigger Mode) can be used with 1PPS IN.

If coarse synchronisation to your system is sufficient, the methods described above may be used with no additional considerations. However certain fixed delays, and uncertainties of the order of 100ns will exist.

To get precise synchronisation you must supply the GSS6100 with an external 10MHz frequency reference and observe certain timing requirements between the 1PPS IN and/or TRIG IN signals and the EXT REF IN signal. The following sections detail these requirements.

Note this is a 50Ω input and the pulse width of incoming signals should be ≥120nsecs.

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5.6.1 1PPS IN

The required timing of the rising edge of 1PPS IN with respect to EXT REF IN, and the resulting timing of the start of operation is shown in

Figure 5-19. Provided these timing requirements are adhered to, the RF signal timing will be fixed and repeatable with respect to REF IN every time an operation is run.

The EXT REF IN signal may be a square wave as shown, (for example a TTL/CMOS signal) or a sinusoid. Whatever the REF IN input waveform, the timing reference point is the ac zero crossing of the signal. Note that alignment of 1PPS OUT as shown in the diagram does not occur immediately, but one second after 1PPS IN is detected. Note also that the 1PPS IN input is disabled whilst an operation is running, i.e. synchronisation can only take place whilst in the HALTED state.

Figure 5-19 Timing requirements for 1PPS IN and resulting start

timing

Timing requirements for 1PPS IN:

EXT_REF_IN_(10MHz

thold (20 ns min)

tsetup (10ns min)

1PPS_IN

(Internal_10MHz_clock)

One second later 1PPS OUT will be aligned as follows:

1PPS_OUT

Start of simulation:

Simulation_state

RF_State

RMED

RMED RUNNING

5.6.2 TRIG IN – Immediate Mode

When using the Immediate Trigger mode, the timing requirements for the rising edge of TRIG IN with respect to EXT REF IN are the same as for the 1PPS IN input (i.e. 10ns setup, 20ns hold). However there is a delay of six

The delay between the 1PPS OUT rising edge and its resulting phase transition at RF, seen

at the RF Output Port, is nominally 0secs ±5 nsecs (1σ) RSS

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10MHz clock cycles after the trigger is recognised before the operation starts. This is shown in

Figure 5-20.

Figure 5-20 Timing requirements for TRIG IN (Immediate Mode) and resultant start timing

XT_REF_IN_(10MHz)

thold (20 ns min)

TRIG_IN

Internal_10MHz_clock

1PPS_OUT

tsetup (10ns min)

Simulation_state

RF_State

RMED

RMED RUNNING

5.6.3 TRIG IN – Delayed Mode

In delayed trigger mode, to start on a defined 1PPS event, the rising edge of TRIG IN must occur at least 1.1 milliseconds before the 1PPS OUT rising edge.

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Chapter 6: Remote interface

The GSS6100 can be remotely controlled using the IEEE-488 bus or RS232 serial port

; an identical set of control commands are used for each interface

type.

6.1 Interface Types

6.1.1 GPIB

The IEEE Std 488.1 Interface Functions subsets implemented are: SH1, AH1, T6, TE0, L4, LE0, RL0, PP0, DT0, and C0.

Limited Query/response message handshakes are implemented for the initial release. Status indication is provided by bit settings of the standard IEEE488 serial poll register to enable the remote controller to monitor basic operation only.

6.1.1.1 Default IEEE-488 address

The GSS6100 is delivered with the IEEE-488 Primary Address set to 02. This may be inspected and changed if desired with either the SimCHAN software over the USB or directly by the GPIB command on the IEEE.488 interface.

To set the address with SimCHAN, start the SimCHAN software and connect the GSS6100 via the USB. Select ‘Hardware Settings’ on the Options menu. The current address is displayed and an alternate address may be selected from a dropdown list. Select OK or Apply to effect the change.

6.1.2 RS232

The serial port is configured to 38400 BAUD, with 8 data-bits, no parity and 1 stop bit. No handshaking is implemented.

Either of the communication interfaces may be used one after the other as long as ONLY one

interface is used at a time.

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6.2 Command set

All messages are initiated by an ASCII character identifier, such as IDEN, of at least 4 bytes in length. This may be followed by a variable number of ASCII encoded parameters depending on the message type, each separated by one or more space characters.

Several messages may be sent in a single transfer but they must be separated by one or more space characters, and the complete transfer must end with EOI asserted for IEEE or <CR><LF> for RS232. The maximum length of a message transfer must not exceed 256 bytes; if it does the entire transfer will be discarded.

The maximum length of each ASCII encoded parameter is 9 bytes (digits) for integer parameters and 64 bytes for floating point parameters (up to 9 decimal places).

Floating point parameters may be supplied in integer or floating point form. Values will be limited to the ranges and precision stated. Units will be as stated, qualifying unit codes are not permitted or recognised.

The query response remains valid until one of the following occur; the response is read, another command query message is received; the RSET command is received; a DCL or SDC (IEEE only) command is received.

IEEE query responses have EOI asserted on the last byte of the response and RS232 responses are terminated with a <LF> character.

6.2.1 Notes on the syntax definition

The following syntax elements are used to define the command set options and constraints.

The short form of terms is indicated in capitals. Otherwise the names are not case sensitive.

Parameter values are separated from the sub command string by white space.

[] Items in brackets are optional.

| Indicates a choice of items, one of which must be supplied

<> These items are to be replaced by numeric values etc.

{} Groups Items to form a single syntax item

… Ellipsis indicates an inclusive range of values

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6.2.2 *IDN?

Query IEEE-488 Device ID String

This query is sent by some IEEE-488 Controller applications, e.g. National Instruments Test and Measurement Explorer, to identify devices on the IEEE-488 bus. The device responds with a user-friendly name in ASCII.

The message format is:

*IDN?

Response:

Where

<Manufacturer> is Spirent Communications

<Model> is GSS6100

<serial number> is the serial number or zero if not known

<firmware> is the firmware or software revision level, or zero if not known

Example Response:

Spirent Communications, GSS6100,1234,1-01

6.2.3 ARMS

Prepare to Run

This command informs the signal generator that all the initial conditions for the operation are complete, and that the signal generator should prepare for a run command (RUNS).

The message format is:

ARMS

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6.2.4 BITE

Query the Bite Status

Commands the device to return the state of the various BITE (i.e. error) flags encoded in an ASCII string. The BITE flags indicate various status and error conditions.

The response format varies according to the device type.

The message format is:

BITE ?

Response:

Refer to

Appendix E:.

On the GSS6100 BITE conditions cause the front panel HEALTH LED to flash and the appropriate flag in the BITE response becomes set. In general, both the LED flashing condition and the flag in the BITE response are reset by querying the BITE. Certain fatal conditions are not cleared by querying BITE. To query and clear Command Syntax errors use the SERR command,

6.2.27. An exception to the above is the external reference out of lock

see indication, where the LED will stop flashing and the flag in the BITE flag is cleared when lock is achieved without the need to query BITE, provided the unit is in the Halted state. If an out of lock condition occurs in the Armed or Running state the flashing LED and BITE flag are latched until queried.

6.2.5 COSW

PRN Code Enable/Disable

Commands the device to transmit or suppress the PRN code modulation. The code signal sequence progresses whilst modulation is suppressed. Note that Nav Data modulation is controlled separately (see NDSW)

The message format is:

COSW <code>

Where <code>

0 PRN code turned off

1 PRN code turned on. This is the default state.

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6.2.6 EREF

Set External Reference Frequency

Sets the expected External Reference Frequency to the specified value. The value is stored in non-volatile memory for use on power-up. The unit automatically switches to external reference and seeks Phase Lock whenever a signal is present on the rear panel connector.

The message format is:

EREF 1MHz | 5MHz | 10MHz

Note the parameter is an ASCII string and must be exactly as shown.

6.2.7 EREF ?

Query External Reference Frequency

Commands the unit to return an ASCII string describing the current External Reference Frequency setting and the lock status.

The message format is:

EREF ?

Example Response:

EREF 10MHz INT or

EREF 10MHz EXT UNLOCKED or

EREF 10MHz EXT LOCKED

6.2.8 GPIB

Set the GPIB Primary Address

Set the IEEE-488 bus Primary Address of the device. The Primary Address is saved in non-volatile memory. The unit is supplied with the IEEE-488 address set to 2. The change takes immediate effect and remains in force indefinitely.

The message format is:

GPIB <gpib address>

Where

<gpib address> An integer in the range 1 to 30.

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6.2.9 HALT

Stop the GSS6100

Commands the device to terminate the current run and return to the Idle State. The Z count and Week Number return to the values used to start the run and the trigger mode is reset to 0 (disabled). All other settings remain unchanged.

The message format is:

HALT

6.2.10 IDEN

Query the Unit Configuration Details

Commands the device to return an ASCII string describing the Unit’s identification, and the firmware release numbers.

The message format is:

IDEN

Example Response:

Type GSS6100

Serial Number 0001

Firmware Issue 1.00

Motherboard Revision 1

6.2.11 IPRG

Set Initial Pseudorange

Sets the initial pseudorange. This is manifest as a time delay relative to the 1PPS OUT signal.

The message format is:

IPRG <initial pseudo range>

Where

<initial pseudo range> an integer in the range 0 to 99999999 meters

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6.2.12 LEVL

Set the RF Output Power Level

Sets the power level for the RF signal at the front panel RF output. The setting is relative to a base level of –130dBm. The command accepts any value but clips this to the maximum level, if applicable, and rounds to the stated resolution.

The message format is:

LEVL <rf power>

Where

<rf power> A floating point number specifying the level in dB.

Range +20.0 to –20.0 to a resolution of 0.1 dB.

6.2.13 LEVL ?

Query the front panel RF signal power level.

Commands the unit to return an ASCII string detailing the current RF signal power.

The message format is:

LEVL ?

Example Response:

LEVL –5.6

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6.2.14 MODE

Set the operational mode

Commands the unit into AutoGO mode. A running channel is not halted by sending the MODE command.

The message format is:

MODE <type>

Where

<type> 1 Sets unit into normal operation.

2 “<string>” Sets unit into AutoGO mode. Signal Generator

configuration is controlled by <string>, e.g. SVID 5 LEVL 0.To action a new script the GSS6100 must be powered cycled. No error checking applied. To initiate an automatic run, the entered “string” must complete with ARMS RUNS.

e.g. To achieve PRN 5, power level +15dB, Doppler velocity 100 m/s. Use the following:

SVID 5 LEVL 15 VCTY 100 ARMS RUNS

6.2.15 MODE ?

Query the current operational Mode.

This command will not affect a running channel

The message format is:

MODE ?

Example Response:

MODE 1

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6.2.16 NDSW

Enable/Disable the Navigation Data Message

Commands the device to transmit or suppress the Navigation Data Message. The message bit sequence progresses whilst the message is suppressed during an operation.

The message format is:

NDSW <code>

Where:

<code> 0 Suppress transmission of the message

1 Transmits the message

6.2.17 NMOD

Modify the Navigation Data generated from a Nav data template

To ensure there are no data conflicts, the GSS6100 firmware must receive the NMOD command at least 6 seconds before the end of a NAV frame boundary. A flag in the “NMOD ?” response indicates if the GSS6100 can accept updates.

New NMOD commands received by the GSS6100 are entered into a ‘user’ table. At the end of every 30 s frame, the entries in the user table are copied into a working table used to modify the next frame of data.

The GSS6100 can hold up to 16 entries.

Note: Some NMOD commands, for example IODE and IODC, use two entries.

The message format is:

NMOD { ? | <Se Wf Bg Lh {value | * }> <$field {value | *}> …}

Note: The NMOD command will accept data in two formats, you can mix the two formats in one command string, as detailed below:

The first format is the general format <Se Wf Bg Lh {value | *}>.

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Where:

Se Defines the sub-frame to be altered. ‘e’ is a decimal number in the range 1 to 3

Wf Defines the word to be altered. ‘f’ is a decimal number in the range 1 to 10

Bg Defines the start-bit in the word. ‘g’ is a decimal number in the range 1 to 24

Lh Defines the number of bits to be altered. ‘g’ is a decimal number in the range 1 to 24

value Is a decimal representation of the Lh bits. The value is read as a signed 32-bit integer. The bottom Lh bits of the 32-bit signed number will be used. If a ‘*’ character is used instead of a decimal value, the entry matching the S,W,B and L values will be removed.

Note: This format lets you modify any valid string of bits.

The second format is more specific <$field {value | *}> and you can modify specific sequences of bits.

Where:

field Is the name of the NAV data field to be altered

Table 6-1 shows the supported fields and their bit assignments

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Table 6-1 - NMOD supported fields

Field Sub-frame word Start-bit length

TOC 1 8 9 16

AF2 1 9 1 8

AF1 1 9 9 16

AF0 1 10 1 22

IODE

3 10 1 8

SVH 1 3 17 6

1 3 23 2

IODC

1 8 1 8

Note: IODC and IODE have two entries in the table, because IODE appears in two places in the NAV frame; and the IODC value is split with the 2 MSBs in one word and the 8 LSBs in another word.

You need only send one NMOD command and the firmware will enter/delete all the correct fields.

Example messages:

NMOD $TOC 24 S1 W3 B4 L3 4

In response to an “NMOD ?” command the GSS6100 will return a response with the following format:

NMOD update zcnt entries

Where:

update A decimal value in the range 0 to 1. ‘1’ indicates new entries may be sent ‘0’ indicates new entries may not be sent.

zcnt Represents the Zcount of the next 30s frame of data to be generated.

entries Indicates how many entries are in the NMOD working table.

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6.2.18 NSAV

Save Navigation Template

Commands the device to record and save a Navigation Message template 'file'. A sequence of messages are sent to first select one of the eight template files, then send text for that file, and finally save the text in the template file. The template information is multi-line ASCII text and is sent sequentially line by line using the NSAV #FILE.TEXT# message. The sequence of messages must be terminated by the NSAV #FILE.SAVE# message. Each individual message must not exceed 256 characters in length including the line terminating ‘newline’ character. The complete file must not exceed 32 Kbytes including comments.

The message formats are:

NSAV {GPS | SBAS} <template>

NSAV #FILE.TEXT# <text>

NSAV #FILE.SAVE#

Where:

<template> Integer value as one of 0 | 1 | 2 | 3.

<text> A line of text to be stored in the currently selected template.

The format rules of each line of text are as follows.

All lines must end with a newline character. Any line starting with a ! is deemed to be a comment. All other lines contain data.

Further details are given in

0 and 0, plus the example files supplied.

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6.2.19 NSAV ?

Query Navigation Template

Commands the unit to return the GPS and SBAS template information.

The message format is:

NSAV ?

The GSS6100 will reply to the query with the size (in bytes) and title string for each of the GPS and SBAS templates.

GPS 0 6995 !NAV_DATA.NAV GPS 1 6995 No Record GPS 2 0 Empty GPS 3 0 Empty SBAS 0 25889 !SBAS_CN3.WAS SBAS 1 0 Empty SBAS 2 0 Empty SBAS 3 0 Empty

Templates marked “No Record” were downloaded with earlier firmware versions and no record was stored.

6.2.20 NSEL

Select Navigation Template

Commands the device to generate the Navigation Message from the named template. The unit has the capability to store four templates for each of GPS and SBAS mode. The unit is supplied with the default navigation message stored in <template> = 0.

The message format is:

NSEL {GPS|SBAS} <template>

Where

<template> Integer value as one of 0 | 1 | 2 | 3.

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6.2.21 PFIL

Select pre-defined Velocity Profile

Commands the device to use a named set of parameters for generation of the next velocity profile sequence. In the GSS6100 these sets of parameters are incorporated in the firmware.

The parameter sets each comprise four floating-point values that together define the profile. Section

5.2.2.1 gives a detailed description of the profile

shape and its relation to the four parameters.

The selection remains effective until the next RSET, PROS or PFIL command is processed or the device is powered down.

The message format is:

PFIL <profile name>

Where:

<profile name> PROF1 | PROF2 | … | PROF8

An ASCII string defining the standard profile to be applied.

The PROF1 values will be applied by default.

6.2.22 PROF

Enable/Disable Velocity Profile

Commands the device to either commence or terminate a velocity profile sequence. The sequence will be either the most recent sequence selected/defined by the PROF or PROS commands or the default sequence defined by PROF1.

The message format is:

PROF <code>

Where:

<code> 1 Initiates the velocity profile sequence. 0 Aborts an active sequence.

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6.2.23 PROS

Select Velocity Profile Parameters

Commands the device to generate the next velocity profile sequence from the supplied parameters. The supplied parameters are not stored permanently. It is recommended that this command be sent just prior to each occasion the Velocity Profile is enabled by the PROF command.

The message format is:

PROS <jerk amplitude><max accel><period const accel><period const vel>

Where:

<jerk amplitude> floating point number in the range: -100 to +100 m/s

<max accel> floating point number in the range: -100 to +100m/s

<period const accel> floating point number in the range: 0 to 540 s

<period const vel> floating point number in the range: 0 to 540 s

6.2.24 PRTY

Enable/Disable Set Parity State

Selects the Navigation Message Data Parity as either Normal (as per ICDGPS-200) or Inverted.

The message format is:

PRTY <code>

Where

<code> 1 Set Message Parity to Normal

0 Set Message Parity to Inverted

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6.2.25 RSET

Reset Device

Commands the device to reset its parameters and operating condition to the power up state. In practice, HALT and RSET perform quite similar functions, with the exception that RSET defaults all parameters to a known state.

The message format is:

RSET

6.2.26 RUNS

Begin operating

Commands the device to start running in operation mode.

The message format is:

RUNS

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6.2.27 SERR

Query and Clear Syntax Error

Commands the device to return the state of the Command Error flags, encoded in an ASCII string, together with a string describing the error(s) and the Command String that caused the error.

The message format is:

SERR ?

Example Response:

SERR 00000001 0, Command not recognised WEAK 987

6.2.28 G2D

Select PRN by G2 Delay

Commands the device to use a specific G2 delay for its C/A code generator.

The signal generator is capable of generating any one of the 1023 possible random sequences associated with the GPS C/A encoder. Each sequence or code is determined by the start conditions of the G1 and G2 coders. The G1 encoder is hardwired to start in the all one state, the G2 encoder, can start in any state except all zeros. The G2 start conditions can be described by a ‘G2 delay’. This G2 delay can take on values between 0 and 1022. Some of the 1023 codes (mainly codes with good orthogonal properties i.e. Low cross correlation) have had assigned to them PRN numbers. To select one of these codes it is easier to use the SVID command.

The message format is:

SG2D <g2delay>

Where

<g2delay> Integer in the range 0 to 1023

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6.2.29 SIGT

Signal Type

This command defines the required signal type, SBAS or GPS. This setting determines the form of the Navigation data message transmitted.

The message format is:

SIGT GPS | SBAS

6.2.30 SNUM ?

Query the Device Serial Number

Commands the device to return its serial number.

The message format is:

SNUM ?

Response

An ASCII string of the form 0999.

6.2.31 STAT

Query Status Flags

Commands the device to return the content of the Serial Poll Status Register in an ASCII string as two hexadecimal digits together with the name of the operating state. The status register may also be read by a Serial Poll, see section

0 for the definition of the status bits.

The message format is:

STAT ?

Response:

STAT <hexbyte> <state>

Where:

<hexbyte> is a representation of the 8 bits of the status byte using hexadecimal digits.

<state> An ASCII string which may one of:

HALTED or ARMED or RUNNING

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6.2.32 SVID

Select PRN by SVID

Commands the device to generate the PRN sequence for the specified Satellite ID number as specified in ICD-GPS-200 (GPS) or RTCA-DO229 (SBAS).

The message format is:

SVID <gps prn> | <sbas prn>

Where

<gps prn> Integer in the range: 1 to 37

<sbas prn> Integer in the range: 120 to 138

6.2.33 TIOP

Select 1PPS Output Signal

Selects the format of the signal generated on the rear panel “1 PPS out” connector.

The message format is:

TIOP <code>

Where

<code> HIGH – The output is always high

LOW – The output is always low

1PPS – The output is always 1 PPS

GATED – The output is 1 PPS only whilst the operation is running

RISE – The output is a rising edge as the operation starts, returning low when the operation halts

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6.2.34 TIOP ?

QUERY 1PPS Output Signal

Commands the unit to return an ASCII string describing the current TIOP setting.

The message format is:

TIOP ?

Example Response:

TIOP 1PPS

6.2.35 TRIG

Select External Trigger

Select Trigger mode. The selection determines how the device will commence a operation when the RUNS command is applied.

TRIG 0 is the default mode, the device defaults to this for each run, thus the TRIG command is optional if the external trigger is not used. If an Ext Trigger pulse is not applied, send the HALT command to return to the Halted state. Returning to the Halted state resets the Trig mode to 0 (disabled).

The message format is:

TRIG <code>

Where:

<code> 0 Start on next 1PPS event (rising edge) without external trigger

1 Start immediately on a rising edge on the External Trigger input

2 Start at the next 1PPS event following a rising edge on the External

Trigger input

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6.2.36 VCTY

Set Doppler Velocity

Commands the device to simulate the specified Doppler velocity settings. If the required Doppler is specified by a single unqualified value then this is applied as both code and carrier Doppler Velocity. Different Doppler settings for code and carrier may be specified if required.

The difference between the CODE and CARR Doppler values will be limited to a maximum of +/- 1000.00 m/s.

The message format is:

VCTY <Doppler> | CODE <Doppler> CARR <Doppler>

Where

<Doppler> Floating point number in the range: -15000.00 to +

15000.00 m/s

A positive Doppler figure yields a decrease in the code/Carrier frequency. Both values may be entered to a maximum resolution of 0.01m/s.

The CARR <Doppler> value is constrained to be the CODE <Doppler> value +/- 1000.00 m/s.

6.2.37 WEEK

Select GPS Week Number

Commands the device to commence the next operation run with the Navigation Message set to simulate signals for the week number specified.

The message format is:

WEEK <GPS week number>

Where

<GPS week number> Integer number in the range 0 to 1023

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6.2.38 WRTE

Select SBAS DATA Rate

This command selects the data rate for the SBAS message. Default 250 symbols per second. (This does not have any affect on the GPS data message rate).

The message format is:

WRTE <sbas rate>

Where:

<sbas rate> Integer from the set: 50 | 100 | 125 | 250

6.2.39 ZCNT

Specify the starting time

The command sets the Z Count value that will be inserted in the first frame of the Navigation Data Message at the start of the next operation run. The value should be supplied as a multiple of four and other values will be truncated to a multiple of four.

The message format is:

ZCNT <GPS time into week>

Where

<GPS time into week> Integer in the range: 0 to 403199

The Z Count unit is a period of 1.5 seconds, so that four Z Count units is a period of six seconds.

6.3 Command availability by mode

Some operation information must be defined before the operation is armed and run. This means some commands are only available in certain modes. This is summarised in

Table 6-2.

The Controller application can determine the device's operating state via a Serial Poll.

Note: The device will regard a command it receives in a wrong state as an error. The command will not be executed and an error flag will be set. You can use a Serial Poll to interrogate the error flag.

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Table 6-2 Commands by Mode

IDLE ARMED RUNNING

*IDN? ARMS AUXP BITE COSW EREF EREF ? GPIB IDEN IPRG LEVL LEVL ?

MODE MODE? NDSW NSAV NSAV ?

NSEL PFIL PROS

*IDN? BITE COSW EREF ? HALT IDEN

LEVL LEVL ? NDSW PFIL PROS PRTY

RSET RUNS

SERR ? SNUM ? STAT ?

TIOP ? VCTY

*IDN? BITE COSW EREF ? HALT IDEN

LEVL LEVL ? NDSW PFIL PROF PROS PRTY RSET

SERR ? SNUM ? STAT ?

TIOP ? VCTY

PRTY RSET

SERR ? SG2D SIGT SNUM ? STAT ? SVID

TIOP TIOP ? TRIG

VCTY WEEK WRTE ZCNT

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6.4 Serial poll – status bits

The device status is signalled by setting bits in the IEEE-488 Serial Poll Status Byte Register. The Controller may read this using a Serial Poll command.

Bits 0 & 1 signal the four operating states of the device:

Bit [1:0]

00 Halted (Idle)

11 Armed (Ready to Run)

10 Running

Bit 2 is a Poll Validity flag. The error flag (bit 7) is undefined whilst the Poll Validity flag is reset.

Bit 7 is a Command Error flag. This is set when an erroneous command is decoded. Once set, the bit state is maintained and the front panel health light flashes until a SERR ? is performed to reset the error condition. Note: the BITE query gives additional information on the command or parameter error, which caused the error condition.

6.5 Example command sequences

6.5.1 Example GPS operations

Step 1 – Basic Initialisation

RSET ;Reset Unit (may be omitted if conditions from previous run to be used)

Serial Poll ;Note - Confirm Validity Bit Set

On Not Error ;Check for Error on each command

;Omitted hereafter for brevity only

Step 2 – Set Initial Conditions

WEEK 987 ;If HALT used, reverts to this at end of run

ZCNT 1236 ;Note – Multiple of 4. Reverts on HALT

SVID 12 ;PRN for GPS Satellite 12. Remains set on HALT

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LEVL 12.5 ;RF Output level. HALT keeps setting at end of

run

VCTY 0.0 ;No Doppler on Code or Carrier. HALT keeps setting at

end of run

Step 3 – ARM

ARMS ;Align RF and set Ready to Run

Serial Poll ;Wait until Ready to Run Flags set

On Ready to Run ;When Bit 0 = 1 and Bit 1 = 1

Step 4 – Start Operation

RUNS ;Starts on next internal 1PPS pulse

Step 5 – Vary Level and Doppler as desired

LEVL –15.0

VCTY CODE 500.3 CARR 501.3

;500.3m/s with 1m/s carrier offset

;simulating changing atmospheric delay

Step 7 – Revert to Idle when finished

HALT

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6.5.2 Example with external trigger

Step 1 – Basic Initialisation

RSET ;Reset Operation

Serial Poll ;Note - Confirm Validity Bit Set

On Not Error ;Check for Error on each command

;Omitted hereafter for brevity only

TRIG 1 ;Start immediately on External Trigger

Step 2 – Set Initial Conditions

;or Use Defaults

Step 3 – ARM / RUN Operation

ARMS ;Prepare to run

Serial Poll ;Wait until Ready to Run Flags set

On Ready to Run ;When Bit 0 = 1 and Bit 1 = 1

RUNS ;Set to RUN mode.

Front Panel ‘Active’ LED will be seen to flash. Trigger may now be applied

Serial Poll ;Check Operation is Running

On Running ;When Bit 0 = 0 and Bit 1 = 1

Step 4 – Vary Level and Doppler as desired

LEVL 20.0

VCTY 10.23

Step 5 – Invoke a Doppler Pulse if desired

VCTY –500.00 ;Set Base Doppler Velocity

PFIL PROF2 ;Select Standard Profile No. 2

PROF 1 ;Start Velocity Profile Sequence

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;The Sequence repeats indefinitely

PROF 0 ;Stop the sequence

Step 7 – Revert to Idle when finished

HALT

6.5.3 Example with external signals

Step 1 – Basic Initialisation

Serial Poll ;Read the Status Bits

On Not Idle ;Either Bit 0 or Bit 1 set

HALT ;Force Operation to Idle mode

RSET ;Reset Operation

SIGT ;Select GPS Mode

Serial Poll ;Note - Confirm Validity Bit Set

On Not Error ;Check for Error on each command

;Omitted hereafter for brevity only

EREF 10MHZ ;Seek Lock to External Reference

EREF ? ;Query after 30 seconds

On Lock ;Response = EREF 10MHz

;Response = EREF INTERNAL if

;lock not achieved

TRIG 1 ;Start on External Trigger

Step 2 – Set Initial Conditions

;or Use Defaults

Step 3 – ARM /RUN Operation

ARMS ;Prepare to run

Serial Poll ;Wait until Ready to Run Flags set

On Ready to Run ;When Bit 0 = 1 and Bit 1 = 1

RUNS ;Set to RUN mode.

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Front Panel ‘Active LED will be seen to flash. Trigger may now be applied

Serial Poll ;Check Operation is Running

On Running ;When Bit 0 = 0 and Bit 1 = 1

Step 4 – Vary Level and Doppler as desired

LEVL 20.0

VCTY 10.23

Step 5 – Revert to Idle when finished

6-28 Remote interface

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Chapter 7: Calibration

The GSS6100 employs a digital architecture to produce accurate and stable signals. As such it requires little calibration.

There are just two user adjustments: Frequency and Power.

These are both simple potentiometer adjustments. Test equipment requirements are a suitable frequency counter with a stable reference and an RF power meter respectively.

Spirent recommends these calibrations be performed annually.

7.1.1 Reference frequency calibration

Use anti-static handling precautions during calibration

This requires a frequency counter capable of measuring 10.00 MHz with at least 10 digits of accuracy, for example an HP53131A. The frequency counter should be locked to a frequency standard accurate to < ± 1 x 10 for example an HP5065A Rubidium standard. It is permissible to use a less accurate standard if you are prepared to accept lower frequency accuracy for the signal generator.

a) Turn on the GSS6100 and allow at least 30 minutes for the

internal oscillator to stabilise.

b) Attach the frequency counter to the 10 MHz OUT BNC

connector on the rear panel.

c) Remove ‘Calibration Void if Broken’ label covering from the

10 MHz Ref Cal adjustment port.

d) Use the frequency adjustment potentiometer to achieve a

frequency reading of 10 MHz ± 0.02 Hz.

e) Re-cover the 10 MHz Ref Cal port with an appropriate

calibration label.

This concludes reference frequency calibration.

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Calibration

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7.1.2 Power level calibration

This requires an RF power meter capable of measuring a frequency of

1.57542 GHz and power levels between –50 dBm and –60 dBm, for example an HP E4418B. Ensure that the power meter is calibrated according to the manufacturer’s instructions, including any adjustments for sensor calibration factor and frequency.

a) Turn on the GSS6100.

b) Remove the 50 ohm termination from the MON / CAL port

connector on the rear panel of the unit. Retain for later replacement.

c) Attach the RF power meter to the MON/CAL port.

d) Allow 15 minutes for the GSS6100 to stabilise.

e) Remove the ‘Calibration Void if Broken’ label covering from

the IF Level Cal adjustment port.

f) Select the menu item Options-Power Calibration.

g) Follow the on-screen prompts.

First, SimCHAN sets up a calibration signal on the rear panel MON/CAL port SimCHAN then calculates and displays the power level you must set at the MON / CAL port.

h) Adjust the IF Level Cal potentiometer to get this power level at

the MON / CAL port.

i) You must set this power level to within ±0.05 dB.

j) Re-cover the IF Level Cal adjustment port with an appropriate

calibration label.

k) Remove the RF power meter from the MON / CAL port.

l) Replace the 50 ohm termination on the MON / CAL port.

This concludes power level calibration.

7-2 Calibration

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Appendix A: Installing SimCHAN

The SimCHAN software controls the GSS6100 over the USB bus. The SimCHAN USB interface uses the Microsoft Plug and Play Manager to install the GSS6100 USB driver; so SimCHAN software must be installed BEFORE the GSS6100 is connected to the PC.

The first time the GSS6100 connects to the host PC, the Found New Hardware Wizard installs the required drivers.

A.1 Install SimCHAN

Do not connect the GSS6100 to the host PC.

To install the operating software on your system hard disk, place the supplied CD into the CD-ROM drive. The SETUP program will normally auto-run, if it does not then simply run the application SETUP.EXE in the root directory on the CD.

This will start an InstallShield script that will guide you through the Installation process, see

Figure 7-1 InstallShield wizard - welcome

Figure 7-1.

The Welcome screen confirms that you are about to install the SimCHAN software. Progress through the installation stages by clicking Next. You may change items you have entered or selected by clicking Back.

A-1

Installing SimCHAN

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Click Cancel to abort the installation.

Figure 7-2 to show typical InstallShield wizard screens.

Figure 7-2 SimCHAN licence agreement

The Installation program installs SimCHAN in a sub-folder of C:\Program Files. Click Browse to select an alternative location, see

Figure 7-3.

Figure 7-3 Select installation folder

The Installation program creates shortcuts you can use to start SimCHAN. The name of the shortcut in the Windows Start menu is SimCHAN.

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Alternatively, you can store the shortcut in an existing folder by selecting the folder name from Existing Folders, see

Figure 7-4.

Figure 7-4 SimCHAN shortcut folder

Click Next to begin the installation. The installation loads the following USB driver files:

a) GSS6100.ini, installed in Windows\INF or WINNT\INF

b) GSS6100.sys, installed in Windows\System32\Drivers or

WINNT\System32\Drivers.

After the installation is finished, you do not have to re-boot the PC.

A.2 Removing SimCHAN

The initial installation creates an Uninstall file that identifies the installed files for removal.

Begin the process by either inserting the Installation CD or using the Add/Remove Programs facility in the Control Panel.

The Uninstall program will prompt you to confirm that you wish to uninstall the software. The Uninstall program removes files created by the Installation process and removes any folders created during installation that are empty.

Note: Folders containing files added after installation, such as user created parameter files, will not be deleted when SimCHAN is removed.

Installing SimCHAN

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A.3 First use

When you connect the GSS6100 to the PC for the first time, you will see the Windows XP Found New Hardware Wizard, see

Figure 7-5 to Figure 7-9.

Figure 7-5 Found new hardware wizard - 1

Select No, not this time and click Next.

Figure 7-6 Found new hardware wizard - 2

Select Install the software automatically (Recommended) and click Next.

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Figure 7-7 Found new hardware wizard - 3

Click Continue Anyway

Figure 7-8 Found new hardware wizard - 4

The installation starts. When the installation is completed, click Next

A-5

Installing SimCHAN

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Figure 7-9 Found new hardware wizard - 5

The last window advises you the installation is complete. Click Finish.

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Appendix B: Updating firmware

The current firmware issue may be checked using the SimCHAN menu Options-Hardware Settings, see section

You will not normally need to change or replace firmware.

The GSS6100 Flash memory device is capable of holding multiple application images. A default image is loaded during manufacture and never overwritten. Further images may be stored at different re-programmable memory locations. The boot code will always check for a new image and run it if found. If the boot code does not find a new image, it runs the default image.

You can upgrade the GSS6100 firmware in the field. Spirent make upgrades available under Warranty or a Support agreement and these upgrades will be available on suitable media or from an FTP site. The Spirent Support Team will provide full instructions if your GSS6100 needs a firmware upgrade.

You must apply GSS6100 firmware updates using the USB bus.

To update the GSS6100 firmware:

a) Close all instances of SimCHAN on the host PC.

b) Connect the host PC to the GSS6100 using the USB bus.

5.5.

c) Start the update utility by clicking on Start-All Programs-

SimCHAN-Flash Memory Update Tool.

d) In the Open dialog box, navigate to the update file, see

7-10.

e) Select the firmware update file, in this example a file of type

*.bin.

f) Click Open.

g) Check the firmware file you selected is the file you want to

install, see

Figure 7-11.

h) Click Load.

i) Loading the firmware takes around 15 seconds. The utility

displays a progress indicator and a message displays when installation is complete, see

j) Power cycle the GSS6100 to load the new firmware and

complete the upgrade.

Figure

Figure 7-12.

B-1

Updating firmware

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Figure 7-10 Open update file

Figure 7-11 Firmware ready to load

Figure 7-12 Firmware update complete

B-2 Updating firmware

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Appendix C: Connecting a GPS receiver

This Appendix has been included to offer the user, new to both GPS Signal generators and/or Receivers, basic guidance on how to set up and track GPS signals.

The signal input on a GPS receiver typically falls into one of three types.

An input socket for a passive antenna.

An input socket for an active antenna/pre-amplifier combination.

A built in antenna only with no input connector (some handheld receivers).

Determine which category your receiver fits and proceed as follows:

Type 1) Connect the receiver directly to the front panel RF OUTPUT connector

using a suitable cable.

Type 2) Use an AC coupled amplifier with equivalent gain and noise figure to

that used by the active antenna. This amplifier can be powered either from an external power supply or from the receiver supply intended for the active antenna. A bias tee/DC block may be required as shown below.

Bias T ee

STR 4500

Receiver antenna port DC & RF

If this is not available an alternative is to use the high

ower MON CAL port at the rear of the signal generator. As the signal is approximately 60dB larger than the front panel signal, attenuation may need to be added.

As the noise floor for both the front and rear panel outputs is governed by the thermal noise of a coaxial attenuator the S/N ratio for the rear

anel is artificially high. For this reason the above arrangement may not

yield an identical receiver performance.

Connecting a GPS receiver

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It is strongly recommended that a DC block is inserted

between the receiver input and any external attenuation as a safety measure.

Type 3) In this case an option is to make or purchase an antenna, for example a

simple dipole, which is attached to the GSS6100 RF output. The antenna is held in close proximity to the receiver. Due to the unknown coupling of this arrangement it may be necessary to either use an external amplifier on the GSS6100 front panel output, or to use the rear panel MON/CAL high level output to provide sufficient signal level. If you wish to construct a suitable dipole, then for the GPS L1 frequency of 1575.42MHz each arm should be approximately 4.8 cm long. A design for a simple dipole follows:

Note that in this mode you are radiating a GPS signal (although at a low level) which could conceivably interfere with local GPS users. At the same time your receiver is susceptible to signals from real GPS satellites. This set-up should therefore only be used in an RF screened environment!

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Appendix D: Signal generator connectivity

Refer to the latest documentation issued by Spirent for details on:

Signal generator specification Spirent specification

Connectivity

Reference

Capability

Reference

Environmental Reference

Signal generator connectivity

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Appendix E: BITE response message

This message returns the current BITE status. This is a verbose; multi-line null terminated string. The first line starts with the message identifier “BITE”. This identifier is followed by an ASCII encoded hexadecimal value indicating hardware BITE errors. For any bit set a verbose string is displayed giving the bit number and error message shown in

The return format is:

BITE 00000010

4 - FPGA_TIMER – Invalid number of ms in second

Message types “info”, “fatal” and “warning” contain information for Spirent use only.

Note: Fatal messages will produce a pop up warning box and terminate an operation if running.

Message type “hardware”, contains BITE information generated by the GSS6100 hardware. You must contact Spirent for all hardware messages except for those in

Table 7-1.

Table 7-2.

Table 7-1 Hardware BITE messages

Displayed string User action

RF-Reference oscillator out-of-lock

Check the external reference is connected and the “hardware settings” options are correctly set.

USB-Error Check USB connection.

BITE response message

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Table 7-2 Bit Interpretation of Hardware BITE Response

Bit String Description

0 MBRD - Wrong issue An invalid Motherboard issue was detected

1 Not Used

2 VPROF - VPROF buffer underrun The GSS6100 ran out of velocity profile data.

3 EEPROM - Attempt to write to locked

EEPROM

4 FPGA_TIMER – Invalid number of ms in

The EEPROM low-level driver attempted to write to the EEPROM when it was locked.

An invalid number of 1 ms pulses was detected in 1 second.

second

5 USB – Receive buffer overflow To much data was received via the USB to fit into one buffer

descriptor.

6 USB – No more receive buffer descriptors

available

The USB receiver ran out of buffer descriptors to store incoming data.

7 USB – Transmit buffer overflow An attempt was made to write too much data to a USB transmit

buffer descriptor.

8 USB – No more transmit buffer descriptors

available

The USB receiver ran out of buffer descriptors to store outgoing data.

9 USB – Error 1: EP0 has stalled A stall was detected on EP0

BITE response message

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Bit String Description

10 USB – Error 2: Program fault. A fault occurred in the USB algorithm.

11 USB – Error 3: Suspend request(?) A suspend request was detected

12 USB – Error 4: Unexpected interrupt An unexpected USB interrupt was detected.

13 RF – Reference oscillator out-of-lock The reference oscillator is out-of-lock

14 RF - LO1 out-of-lock Local oscillator 1 is out-of-lock

15 RF - LO2 out-of-lock Local oscillator 2 is out-of-lock

16 DSP – NAVD underrun A DSP ran out of NAV data

17 EEPROM - Load error There was an error reading from the EEPROM

18 EEPROM - Save error There was an error writing to the EEPROM

19 EEPROM - Invalid contents The firmware detected invalid EEPROM contents

20 TIMER - Timer FPGA load error The firmware was unable to load the Timer FPGA correctly.

21 DSP – DSP FPGA load error The firmware was unable to load the DSP FPGA correctly.

22 Motherboard – Wrong EPLD version An invalid Motherboard EPLD version was detected.

23 DSP board - Wrong EPLD version An invalid DSP board EPLD version was detected.

24 MOD – DSP PLL out-of-lock The Modulator DSP PLL is out of lock

BITE response message

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Bit String Description

25 MOD – DSP PLL Loss of input clock The Modulator DSP PLL has no clock input.

26 MOD – DSP PLL Loss of clock output The Modulator DSP PLL has no clock output.

27 DSP – Wrong issue An invalid DSP issue was detected

28 DSP – Overtemp The DSP has reported an over-temperature problem and

shutdown.

29 EREF – External reference present state

The state of the external reference changed during the run.

changed during run

30 NAVD – End of SBAS correction data The SBAS correction data has been exhausted.

BITE response message

E-4

Spirent GSS6100 User's Guide

Specifications and Main Features

Frequently Asked Questions

User Manual

Chapter 1: General

1.1 Record of issue

1.2 Referenced documents

1.3 Deliverables

1.4 Copyright notices

1.5 Acronyms and abbreviations

1.5.1 Document conventions

1.5.1.1 Software

1.5.1.2 Hardware

Chapter 2: Introduction

2.1 SimCHAN or remote operation

Chapter 3: Hardware overview and installation

3.1 Front panel

3.2 REAR PANEL

3.3 Installation and connection to host PC

Chapter 4: Principles of operation

4.1 Overview

4.2 SimCHAN interface

4.2.1 Controlling the GSS6100

4.2.2 Help

4.2.3 Status bar

Chapter 5: GSS6100 operating details

5.1 SimCHAN toolbar

5.1.1 ARM the GSS6100

5.1.2 RUN the GSS6100

5.1.3 HALT the GSS6100

5.2 SimCHAN main area

5.2.1 Pseudo Range Velocity

5.2.1.1 Velocity increm ent

5.2.2 Velocity profiles

5.2.2.1 More on velocity profiles

5.2.2.2 Profile Data File

5.2.2.3 Carrier Doppler Offset

5.2.3 RF Power

5.2.3.1 RF Power Level Offset

5.2.3.2 RF Power - Level Increment

5.2.4 Simulation Time

5.2.4.1 GPS week number

5.2.4.2 Time of Week

5.2.5 Nav Data Message

5.2.5.1 Message Type

5.2.5.2 Message Parity

5.2.5.3 Message File Template

5.2.6 PRN

5.2.6.1 PRN Number

5.2.6.2 PRN Code On

5.2.7 SBAS Message Rate

5.2.8 Pseudo Range

5.2.9 Time into Run

5.2.10 Prompts, Warnings and Errors

5.3 Navigation Data Template

5.4 AutoGO

5.4.1 Limitations of AutoGO

5.5 Hardware options and settings

5.5.1.1 External T rigger

5.5.1.2 1PPS Out

5.5.1.3 IEEE Primary Address

5.5.1.4 Info Mask.

5.5.1.5 Reference Fre quency

5.6 Synchronisation

5.6.1 1PPS IN

5.6.2 TRIG IN – Immediate Mode

5.6.3 TRIG IN – Delayed Mode

Chapter 6: Remote interface

6.1 Interface Types

6.1.1 GPIB

6.1.1.1 Default IEEE-488 address

6.1.2 RS232

6.2 Command set

6.2.1 Notes on the syntax definition

6.2.2 *IDN?

6.2.3 ARMS

6.2.4 BITE

6.2.5 COSW

6.2.6 EREF

6.2.7 EREF ?