Spirent GSS4100 USER MANUAL

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GSS4100

USER MANUAL

THE INFORMATION CONTAINED IN THIS DOCUMENT IS THE PROPERTY OF SPIRENT COMMUNICATIONS (SW) LIMITED. EXCEPT AS SPECIFICALLY AUTHORISED IN WRITING BY SPIRENT COMMUNICATIONS (SW) LIMITED, 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. © COPYRIGHT SPIRENT COMMUNICATIONS (SW) LIMITED 2001

PROPRIETARY INFORMATION

Issue 1.02, December 2001

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RECORD OF ISSUE

Issue Date Reason for Change

Draft 1.00 June 2001 First issue for initial customer evaluation.

1.00 August 2001 DCR0075

1.01 September 2001 DCR0078

1.02 December 2001 DCR0082, DCR0086

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CONTENTS

1 INTRODUCTION

1.1 GUI OR REMOTE IEEE OPERATION 6

1.2 Referenced Documents 7

1.3 DELIVERABLES 7

2 SOFTWARE INSTALLATION 8

2.1 Software Installation Procedure 8

3 HARDWARE OVERVIEW AND INSTALLATION 13

3.2 Installation and connection to host PC 14

3.3 Safety Notice 16

4 PRINCIPLES OF OPERATION 17

4.1 Overview 17

4.2 GUI Interface 18

4.3 Navigation Data Templates 35

4.4 Hardware Settings Display 37

4.5 Synchronisation 40

4.6 Updating Software 43

5 GPIB INTERFACE & COMMANDS 46

5.2 Command Availability by Mode 62

5.3 Serial Poll – Status Bits 64

5.4 Example command sequences 64

6 HARDWARE CALIBRATION / CONFIGURATION 69

6.1 Introduction 69

6.2 Removing the GSS4100 case 69

6.3 Frequency calibration 70

6.4 Power Level Calibration 71

6.5 BITE Reporting 72

6.6 Upgrading the firmware using the flash memory loader 72

7CONTACTING SPIRENT 74

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TABLE OF APPENDICES

A GLOSSARY 75

B CONNECTING A GPS RECEIVER 76

C SIGNAL GENERATOR CONNECTIVITY 78

D SIGNAL CAPABILITY 80

E ENVIRONMENTAL 81

F GSS4100 BITE RESPONSE MESSAGE 82

G STANDARD GPS NAVIGATION MESSAGE 85

G.1 Introduction85

G.1.1 Telemetry (TLM) Word – All Subrames 86 G.1.2 Handover Word (HOW) – All Subframes 86 G.1.3 Subframe’s 1 through 3 87 G.1.4 Subframes 4 and 5 94 G.1.5 Page ID’s 1 through 32 95 G.1.6 Page ID 51 98 G.1.7 Page ID’s 52 Through 54 101 G.1.8 Page ID 55 103 G.1.9 Page ID 56 105 G.1.10 Page ID 57 108 G.1.11 Page ID’s 58 Through 62 110 G.1.12 Page ID 63 112

H USER DEFINABLE NAVIGATION DATA 116

H.1 Introduction116

H.2 Format of File 116

H.2.1 General 116 H.2.2 Data Fields 117

I SBAS CORRECTION DATA FILES 120

I.1 Creating and Editing a SBAS Correction Data File 120

I.1.1 Example 121 I.1.2 Default *.WAS File, WAAS_DEF.WAS 121 I.1.3 Possible *.WAS Data Errors 142

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LIST OF FIGURES

Figure 1 Installation Welcome 8

Figure 2 Installation Folder 9

Figure 3 Start Menu Folder 10

Figure 4 Confirmation Installation Complete 11

Figure 5 Confirm Uninstall 12

Figure 6 Uninstall Complete 12

Figure 7 SimCHAN Display 18

Figure 8 Control Bar 20

Figure 9 Setting Pseudo Range Velocity 22

Figure 10 Setting Carrier Doppler Offset 24

Figure 11 Setting RF Power Level 24

Figure 12 Setting Simulation Time 26

Figure 13 Setting the PRN 27

Figure 14 Navigation Message Controls 29

Figure 15 Setting SBAS Data Rate 30

Figure 16 Setting the Initial Pseudo Range 31

Figure 17 Warning & Prompts Log Window 32

Figure 18 Velocity Profile Elements 33

Figure 19 Loading a Navigation Message Template 36

Figure 20 Hardware Settings Display 37

Figure 21 Timing requirements for 1PPS IN and resulting start timing 41

Figure 23 Timing requirements for TRIG IN (Immediate Mode) and resulting start timing 42

Figure 25 Open the Update File 43

Figure 26 Firmware Ready to Load 44

Figure 27 Firmware Update Complete 44

Figure 28 Raw SBAS Correction Data Diagram 120

Figure 29 SBAS Message Structure 120

Figure 30 Bit Sequence Message Type 1 124

IBM PC/AT are registered trademarks of International Business Machines Corporation. MSDOS, Windows 95 and Windows 98 are registered trademarks of Microsoft Corporation. InstallShield is a registered trademark of InstallShield Software Corporation.

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1 INTRODUCTION

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Thank you for purchasing a GSS4100 GPS/SBAS Simulator from SPIRENT, world leaders in the field of Satellite Navigation Systems Simulation.

The Global Positioning System (GPS) is based upon a constellation of earth-orbiting 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 GSS4100 fully supports both standard GPS and SBAS.

The GSS4100 is a standalone single-channel L1 C/A code GPS Simulator. It has been designed as precision test equipment for evaluating GPS/SBAS receivers, in the areas of design verification, production test, comparative evaluation, statistical data-generation through extended and repeated tests, and incoming product test.

1.1 GUI OR REMOTE IEEE OPERATION

The GSS4100 can be controlled in one of two ways

• GUI

A user-friendly PC interface broadly based upon Spirent’s STR4775 and STR4500 products. This software package is called SimCHAN and it communicates with the GS4100 via USB.

• IEEE instruction set.

In this mode simulation control is via Spirent’s proprietary IEEE command set. This command set was developed around the GSS4700 product (STR4775 with IEEE control) and as such will mean existing GSS4700 code can be easily ported to the GSS4100.

It should be noted that both modes of operation offer identical control capability.

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1.2 REFERENCED DOCUMENTS

a) ICD-GPS-200 The 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-DO229Minimum operational performance standards for Global

Positioning System/Wide Area Augmentation System Airborne Equipment

1.3 DELIVERABLES

1. GSS4100 GPS/SBAS Simulator

2. User Manual (This book)

4. GSS4100 SimChan software on CD-ROM

5. USB cable

6. Power cables (Country specific)

7. SPIRENT mouse mat

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2 SOFTWARE INSTALLATION

The SimCHAN software controls the GSS4100 via the USB. The SimCHAN USB interface uses the Microsoft Plug and Play Manager to install a GSS4100 USB driver. In consequence the SimCHAN software must be installed BEFORE the GSS4100 is connected to the PC. The Plug and Play system will then automatically install the driver the first time that the GSS4100 USB cable is plugged in.

2.1 SOFTWARE INSTALLATION PROCEDURE

Leave the GSS4100 switched off.

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.

Figure 1 Installation Welcome

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

Figure 2 Installation Folder

The Installation program will offer to install the SimCHAN software in a subfolder of C:\Program Files. You may select another location or folder name by clicking the Browse button.

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Figure 3 Start Menu Folder

The Installation program creates shortcuts that may be used to start SimCHAN. The start menu shortcut will be called SimCHAN and will be placed in a new Spirent Communications folder. You elect to have the shortcut placed in another existing folder by selecting it from the list.

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Figure 4 Confirmation Installation Complete

Once the folder selections are accepted the Installation proceeds to copy the files. In addition to the SimCHAN program files, two driver files are also copied to system folders. A file GSS4100.INF is added to the Windows\INF or WINNT\INF folder and a file GSS4100.SYS is added to Windows\System32\Drivers or WINNT\System32\Drivers. These two driver files will be recognised by the Plug and Play process and become active when the GSS4100 is connected to the USB port.

It will not be necessary to reboot the PC.

If it becomes necessary to remove the SimCHAN software, re-activate the Installation program by either inserting the Installation CD or via the Add/Remove Programs facility in the PC’s Control Panel folder. The initial installation creates an Uninstall file that enables the installed files to be identified and removed.

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Figure 5 Confirm Uninstall

The Uninstall program will prompt you to confirm that you wish to perform this action. The Uninstall program removes the files created by the Installation process and any folders that are thus left empty. If further files have been added to these folders since installation then they will be left in place and the folders will not be deleted.

Figure 6 Uninstall Complete

The Uninstall process will confirm successful completion.

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3 HARDWARE OVERVIEW AND INSTALLATION

This section gives a brief overview of the indicators and connectors on the GSS4100 and how to connect it to the host PC. Signals are fully characterised in the Technical Specifications, Appendices C, D, and E.

3.1.1 FRONT PANEL

POWER

HEALTH

ACTIVE

Primary RF Out

POWER LED ON when power is connected and internal

power supply is operational.

HEALTH LED ON unless the internal monitoring detects:

a) An error, in which case it flashes at a 1Hz

rate.

b) Whilst acquiring external reference lock,

when it flashes at a 4Hz rate.

ACTIVE LED ON when a simulation is in progress. Flashes

when awaiting an external trigger signal on rear panel TRIG IN

Primary RF Output

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‘N’ Type connector

Provides a composite GPS/SBAS signal

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3.1.2 REAR PANEL

HOST (USB)

MON CAL

AUX

OUTPUTS

TRIG IN 10MHz OUTEXT REF IN

HOST (IEEE-488)

Made in U.K.

Connector Type Description

MON/CAL Output SMA female

connector

AUX OUTPUT 25 way Dtype See Appendix C.

TRIG IN BNC Allows an external trigger signal to

EXT REF IN BNC Allows unit to be locked to an

10 MHz OUT BNC Internal OCXO reference output.

HOST (USB) USB

downstream connector

Provides a high level version of the front panel RF output.

start a simulation.

external frequency reference.

Control and data connection to the host PC.

HOST (IEEE488) IEEE488 Control and data connection to the

host PC.

Power

IEC Power in, refer to Appendix C

in/switch/fuse

Further details of these connectors are given in Appendix C.

3.2 INSTALLATION AND CONNECTION TO HOST PC

When the software Installation is complete you may proceed to power on the GSS4100 and connect, via, your chosen interface to the controlling host

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PC, either USB for SimChan Software operation or an IEEE.488 cable for remote control

The power input to the GSS4100 is auto sensing for 100-120V or 220-240V operation. Connect the power cord to the GSS4100.

Turn on the GSS4100.

After a brief power-up sequence the POWER and HEALTH LEDs on the GSS4100 front panel illuminate continuously to show that everything is operating correctly.

If you have opted for IEEE.488 control, the unit is now ready for operation.

If you have opted for SimChan software control the Plug and Play process will recognise that a new device is connected to the USB bus and search for the device’s driver. A message box with the legend ‘Found New Device’ is displayed, this will change to indicate device ‘GSS4100 L1 Simulator’ found and the message box will then close. If you are running Windows 2000 an icon will appear in the system tray on the Taskbar. If you position the cursor over this icon a list of the connected USB devices will appear.

Start the SimCHAN software by double clicking the SimCHAN Icon on the desktop or via the shortcut in the Start Menu.

It should be noted that new users to the GSS4100 may benefit from using SimChan before moving onto IEEE operation as they may find simulation set-up, control and adjustment via the GUI initially more instructive.

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3.3 SAFETY NOTICE

PRODUCT TITLE : GPS/SBAS SIMULATOR

PRODUCT CODE : GSS4100

DATA SHEET No : N/A

PRODUCT SAFETY INFORMATION SHEET

This safety Information Sheet should be read in conjunction with the Product Data Sheet (where applicable).

Failure to observe the ratings and the information on this sheet may result in a safety hazard.

This PSIS applies to the signal generator unit of the simulator only. For information on the computer workstation (where applicable) see safety section of the manufacturer’s handbook.

1.MATERIAL CONTENT This unit contains Printed Circuit Board semi-conductor assemblies. Materials contained within the unit include PTFE, ABS and epoxy/glass laminate.

2.PHYSICAL FORM The equipment is housed in a vented aluminium enclosure. Enclosure dimensions are 99mm(h) x 345mm(d) x 254mm(w) (approx). Total weight of the Simulator Unit is 5kg (approx).

3.INTRINSIC PROPERTIES

(a) Non-operating Safe, when isolated from primary power source.

(b) Operating Removing fixed panels during operation presents an electric shock hazard. Fixed panels may only be removed by suitably qualified personnel. High voltage hazard warning labels are affixed to the outside of the Unit.

WARNING: This equipment must be earthed.

4.FIRE CHARACTERISTICS

Primary Overload conditions could present a fire hazard. The limiting oxygen index value of the glass/epoxy laminate is 25-32. Protection circuits incorporated minimise the overload and/or component failure hazards. The case is vented to minimise heat and gas concentration.

(b) Secondary Under overload conditions the external finishing paint will burn. Excessive overload/heating of materials will cause emission of toxic gases.

5.HANDLING The unit is sensibly robust but dropping or excessive vibration may lead to immediate damage or later component failure with consequent damage. The portable unit weighs 5kg (approx). The unit is supplied in an approved design package to minimise damage in transit.

6.STORAGE Care should be observed when storing to ensure units cannot be subjected to environmental conditions in excess of those given in the relevant data. Units should not be stored in conditions exceeding the temperature range of -20°C to +60°C.

7.DISPOSAL Disposal of the unit should be accordance with the toxic waste disposal procedure, current at the time of disposal. Units must not be incinerated due to the presence of PTFE which would emit toxic fumes.

8.UNSAFE USE Electric shock hazard is present if panels are removed during operation. Fire hazard could occur during overload conditions. Replacement fuses should be of the correct rating and type to minimise overload conditions. Toxic fume hazard possible if unit is overheated from internal or external source. Mechanical hazard can occur if the unit is mishandled or incorrectly secured. Under damage conditions do not use.

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4 PRINCIPLES OF OPERATION

4.1 OVERVIEW

The GSS4100 Simulator requires instructions to configure and commence a simulation, from either the SimCHAN software via the USB or by command sequences transmitted to the IEEE.488 (GPIB) port.

Regardless of which method of control is selected the simulator has three software states, Halt, Arm and Run.

Essentially, whilst in the Halted State the user configures the next simulation run, i.e. selects 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 all those attributes have been set, the simulator is ARMed. The ARM mode is an interim step prior to RUNing to configure the hardware and to allow the user an opportunity to make any final adjustments to certain parameter types. Finally, once in the RUN state the Simulator is actually operational, i.e. the all requested simulation characteristics will be present on the RF output port. Whilst in the RUN mode many parameters can be re-adjusted and controlled to suit whatever simulation profile is required. At the end of the run the simulator is again Halted and the process repeated as required.

Now that the basic fundamentals have been considered the following subsections work through each of the available simulation and hardware control parameters. For clarity these descriptions revolve around the GUI software, but for ease of use a cross-reference to all applicable IEEE control commands is also included.

A full alphabetical listing of all the IEEE control commands can be found in section 5.

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4.2 GUI INTERFACE

Figure 7 SimCHAN Display

The SimCHAN software allows the operating parameters of the GSS4100 to be set and adjusted in real time and any responses to be displayed.

The display has three main elements:

• The Outer Frame with Drop Down Menus and Toolbar,

• The main Control Display,

• Status Bar

4.2.1 ENTERING PARAMETERS

The interface uses a combination of the standard Windows Edit fields, toggled button controls, and drop-down list selection controls.

Data values may be entered directly to the Edit fields by selecting the field, typing the value and then pressing the Enter key. Alternatively most fields are equipped with Spin button controls (Up/Down arrow buttons) that can

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be selected to scan through the range of allowed values. The Spin buttons may be operated by the mouse or by the keyboard cursor keys. The Velocity and RF Power fields each have an associated Increment field that adjust the step size of changes to the main Velocity and RF Power ranges. This allows the Velocity & RF power fields to be varied by both fine and coarse increments. The RF Power may also be set by the horizontal slider control.

Some parameters have just two states and these are operated by selecting the Check marks on or off to enable or disable the function.

Other multiple choice selections are made from drop-down lists. Here the user opens the list and then picks one of the options to become the active selection.

4.2.2 CONTROLLING SIMULATIONS

The Arm, Run and Halt control actions may be invoked in each of three ways to suit user preference:

By selecting with the mouse or keyboard from the Run Menu.

By clicking the buttons of the application Toolbar.

By the Hot keys: Ctrl+A, Ctrl+R and Ctrl+H.

In common with most Windows applications you may find that the mouse is the most useful method of control.

N.B. Due to a limitation of the Windows interface the Hot keys and keyboard menu actions are only effective when the application frame is active, i.e. the Title bar is highlighted. The standard Windows Hot key Alt+F6 toggles the frame to the active state.

4.2.3 CONTEXT SENSITIVE HELP

The standard Windows Help key F1 will activate the Windows Help facility and locate the topic appropriate to the Application element in use.

In addition the Status bar will show a prompt appropriate to the screen element under the mouse cursor.

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4.2.4 STATUS BAR

In addition to the Quick Help prompts the Status Bar has fields that show:

• The Application/ Simulation state,

• Internal/External Frequency Reference signal,

• Presence of a working USB connection.

4.2.5 MAKING AND USING STANDARD SIMULATIONS

The Control application follows the document paradigm. As the user applies parameter settings these are recorded in an internal document. This document may be saved to disk using the File menu options, and is given the extension .GSS by default. Documents saved in this manner may be loaded while the application is not running a simulation thereby setting the simulation parameters to a known state with the minimum of effort.

Following this document analogy the New document options reset the application parameters to the basic default states.

4.2.6 SELECTING GPS OR SBAS SIMULATION MODE

[IEEE Command: SIGT, see section 5.1.28]

Under the Nav Data Message settings for Message Type, select either GPS or SBAS from the drop-down list.

On the GPS setting the RF signal from a GPS type satellite will be simulated and the control options appropriate to GPS are activated.

On the SBAS setting the RF signal from an SBAS type satellite will be simulated and the control options appropriate to SBAS are activated.

4.2.7 SIMULATION CONTROL

The primary method of control is via the application Toolbar.

Figure 8 Control Bar

The toolbar offers a quick method to execute the basic control functions of ARM, RUN and HALT.

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It also gives access to the document functions of:

New Close any open parameters document and Reset Simulation

Parameters.

Open Offers the standard Windows document location Window to

select a file.

Save Records the current parameters to an open file or prompts for a

new name.

4.2.7.1 ARM the Simulation

[IEEE Command: ARMS see section 5.1.5]

Select the ARM button to load the selected simulation parameters to the GSS4100 and to prepare for a simulation run. Completion of the Arming sequence is indicated by the Status ‘Ready to Run’.

4.2.7.2 Start the Simulation Running

[IEEE Command: RUNS see section 5.1.25]

This button releases the GSS4100 to begin the prepared simulation.

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Independent of mode (see section 4.4.1.2) the user must use this button to start the simulation. It should also be noted that the front panel ‘Active’ LED will become illuminated

. To return to the idle state without running the

simulation, select the Halt button.

4.2.7.3 Halt the Simulation

[IEEE Command: HALT see section 5.1.11]

The Halt button aborts the simulation in progress or terminates the Ready to Run state and returns the Application to the Idle state, allowing parameters to be altered if desired.

4.2.8 PSEUDO RANGE (DOPPLER) VELOCITY

[IEEE Command: VCTY see section 5.1.355.1.33]

This value 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.

Figure 9 Setting Pseudo Range Velocity

The velocity may be set by typing the desired value and pressing the Enter key or by clicking the Up or Down arrow buttons next to the value. On clicking these buttons the value shown in the Pseudo Range Increment field will be added or subtracted to the Pseudo Range Velocity.

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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4.2.8.1 Stepping Rate for the Pseudo Range Velocity

This value is added or subtracted from the Pseudo Range Velocity when an Up or Down arrow next to the Pseudo Range value is clicked.

The value may be set to any value in range by typing a new value and pressing Enter or by clicking on the Up or Down arrow buttons next to the value.

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

4.2.8.2 Stepping through the Range of Pseudo Range Velocity

The Up and Down arrow controls next to the Velocity display may be used to step the velocity from –15000.00 through to +15000.00 m/s. The step size may be adjusted by setting the Increment value in the control below.

When the Pseudo Range Velocity edit box is the active control (i.e. its value is highlighted) the Up and Down arrow controls will respond to the keyboard up and down cursor keys in addition to mouse clicks when the screen cursor is placed over the up or down control.

4.2.9 ENABLE OR DISABLE A VELOCITY PROFILE

[IEEE Command: PROF see section 5.1.21]

This option only becomes available when the simulation is running.

On selecting this option the Profile with the identifier shown is activated and used to superimpose a cyclic sequence of changes to the Pseudo Range Velocity in force.

The sequence will continue to be applied until the user cancels this option.

4.2.9.1 Selecting the Required Velocity Profile

[IEEE Command: PFIL see section 5.1.20]

Click on the arrow button to show a drop down list of the Profile Identifiers available.

Eight standard profiles (PROF1 through PROF8) are incorporated in the GSS4100 firmware.

These correspond to the Standard Receiver Performance Test profiles defined in ICD-GPS-204.

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4.2.10 CARRIER DOPPLER OFFSET

[IEEE Command: VCTY see section 5.1.35]

Figure 10 Setting Carrier Doppler Offset

The Carrier Doppler Velocity 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 value has a range from –1000.00 through +1000.00 to a resolution of

0.01 m/s.

It may be set by entering a value and pressing the Enter key or by selecting the Up and Down arrow buttons next to the control. The buttons also respond to the keyboard up/down cursor keys.

4.2.11 RF POWER LEVEL

[IEEE Command: LEVL see section 5.1.14]

Figure 11 Setting RF Power Level

The RF Output power level may be varied to + or – 20.0 dB of the base level to a resolution of 0.1 dB.

The level may be set by entering a value and pressing the Enter key on the keyboard, by clicking and holding the Up/Down arrow buttons next to the control or by dragging the associated slider control. The buttons also

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respond to the keyboard up/down cursor keys when this is the active control. If a value is entered that is outside the allowed range, it will be truncated to the limit value.

The Up and Down buttons increment and decrement the level by a value defined by the step size control below the level control. The Up or Down buttons just add or subtract the increment value, the slider also forces the level to a multiple of the selected increment value.

4.2.11.1 Stepping Rate for the RF Power Level controls

A stepping rate or increment value may be set by entering a value and pressing the keyboard Enter key. Any value may be set 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.

4.2.11.2 RF Power Control

The RF Power Slider Control allows the level to be set quickly and easily by either dragging the slider with the mouse cursor or by pressing the left/right keyboard cursor keys. The slider control adjusts the level to values that are multiples of the Stepping Rate defined for the RF Power Level.

If a user defined Stepping Rate is in force, to avoid discontinuities at the range limits the value used is the nearest pre-defined Stepping Rate value rather than the user’s value.

To adjust the power level by fine amounts ensure that a small stepping rate is selected.

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4.2.12 GPS WEEK NUMBER

[IEEE Command: WEEK see section 5.1.36]

Figure 12 Setting Simulation Time

This parameter 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, by typing the number and pressing the Keyboard Enter key or by clicking the Up and Down arrow buttons next to the control. The arrow buttons also respond to the Up and Down cursor keys on the Keyboard.

The Up/Down buttons apply acceleration i.e. the rate at which the week value increments or decrements increases if a button is held for a period, being initially in units, then tens, then hundreds and later in thousands.

4.2.13 TIME OF WEEK

[IEEE Command: ZCNT see section 5.1.38]

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

The time may be entered by typing the desired value and pressing the Enter key or by clicking the Up or Down arrow buttons next to the value. The allowed values range from 0 through 403196 in steps of 4 GPS Epochs.

1 GPS Epoch = 1.5 Seconds

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4.2.14 PRN NUMBER

[IEEE Command: SVID see section 5.1.31 & SG2D see section 5.1.27]

Figure 13 Setting the PRN

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

The PRN value is constrained to the range 1 to 37 for GPS type satellites and 120 to 140 for SBAS satellites.

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

The value may be selected by typing a value and pressing the Enter key on the keyboard or by clicking the Up and Down arrow buttons next to the control. The Up/Down buttons will also respond to the keyboard up/down cursor keys.

4.2.14.1 PRN Code Selection

The GSS4100 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 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. By convention several of the 1023 codes (mainly codes with good orthogonal properties i.e. Low cross correlation) have had assigned to them PRN numbers. The table overpage details the PRN assignments to date.

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PRN No. Assignment

1-37 GPS

38-61 GLONASS

62-119 Future GLONASS

120-140 GEO/SBAS

141-210 Future GNSS/GEO/SBAS/Pseudolites

The SimCHAN software constrains the PRN assignment to the values allocated for GPS or SBAS satellites.

4.2.14.2 Enable or Disable PRN code

[IEEE Command: COSW see section 5.1.7]

PRN code generation may be suppressed by clearing the check mark against the ‘PRN Code On’ button.

This may be achieved by clicking with the mouse or by pressing the Tab key until the ‘PRN Code On’ legend is surrounded by a dashed rectangle, indicating that it is the active control, and then pressing the space bar or by pressing the ‘Hot Key’ Alt+N.

4.2.15 NAVIGATION AND CORRECTION DATA MESSAGES

[IEEE Command: 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

NDSW see section 5.1.15]

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Figure 14 Navigation Message Controls

Generation of the Navigation Message may be suppressed by clearing the check mark against the ‘Message On’ button.

This may be achieved by clicking with the mouse or by pressing the Tab key until the ‘Message On’ legend is surrounded by a dashed rectangle, indicating that it is the active control, and then pressing the space bar or by pressing the ‘Hot Key’ Alt+O.

4.2.15.1 Selecting Parity Normal/inverted for the Navigation Message

[IEEE Command: PRTY see section 5.1.23]

Parity errors may be simulated on the Navigation Message by clearing the check mark against the ‘Message Parity’ button. This inverts each parity bit, thus invalidating it.

This may be achieved by clicking with the mouse or by pressing the Tab key until the ‘Message Parity’ legend is surrounded by a dashed rectangle, indicating that it is the active control, and then pressing the space bar or by pressing the ‘Hot Key’ Alt+P.

Note: The data message is buffered in hardware. When the parity status is changed whilst the simulation is running a delay will elapse before the change is reflected in the RF output. It is recommended that this feature be only set up while the application is idle without a simulation in progress.

4.2.15.2 Selecting a Message Definition file

[IEEE Command: NSEL see section 5.1.19]

The GSS4100 has provision to store up to 8 Message Definition Templates in its Flash memory storage. These memory slots may be filled with four GPS Navigation Message Templates and four SBAS Correction Data

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message Templates. When the GPS constellation is selected then Templates for GPS Navigation Messages are selected; otherwise SBAS Correction Message Templates are selected.

An ID number in the range 0 to 3 identifies the Templates. The Template ID shown will be the active selection during a simulation and used to generate the Navigation/Correction message component of the RF signal.

To select a file using a mouse: click the down arrow button to open the list of file then click on an ID number to make it the active selection.

To select a file using the keyboard: tab through the various controls until the Message Definition file control is highlighted. Then use the up/down cursor keys on the keyboard to move the highlight to the desired ID Number, and then press the Enter key on the keyboard or the tab to mark that ID as the active selection.

4.2.16 SBAS MESSAGE TRANSMISSION RATE

[IEEE Command: WRTE see section 5.1.37]

Figure 15 Setting SBAS Data Rate

The rate may be varied for SBAS type simulations only. The value shown as the active value will control the rate at which the Correction message is transmitted during an SBAS type simulation.

There are four rates available: 50, 100, 125 and 250 data bits per second with 250 bps being set by default, equivalent to 500 symbols per second when forward error corrected.

To select a rate using a mouse: click the down arrow button to open the list of rates then click on a value to make it the active selection.

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To select a rate using the keyboard: tab through the various controls until the Message Transmission Rate control is highlighted. Then use the up/down cursor keys on the keyboard to move the highlight to the desired value, and then press the Enter key on the keyboard or the tab to mark that value as the active selection.

N.B. The Message Transmission rate for GPS satellites is fixed at 50 bps.

4.2.17 TIME INTO RUN IN SECONDS

This shows the elapsed time into the simulation in seconds.

4.2.18 INITIAL PSEUDO RANGE

[IEEE Command: IPRG see section 5.1.13]

Figure 16 Setting the Initial Pseudo Range

This value may be set while the simulation is idle only. It 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 4.4.1.2).

The pseudo range can take any value between 0 and 99999999 metres (equivalent to 333 ms time delay) and has a resolution of 1 metre.

To set the value: select the control with the mouse or by tabbing through the various controls until it is highlighted. Type the required value and press the Enter key on the Keyboard.

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4.2.19 LOG OF PROMPTS, WARNINGS AND ERRORS

[IEEE Command: BITE see section 5.1.6]

Figure 17 Warning & Prompts Log Window

The application will display single line texts describing events that occur during execution of the program. The texts are stored in time sequence with the latest on display. The record of events may be viewed by selecting the down arrow button to open the list and then operating the scrollbar to scan the recorded events.

The record of events may be cleared by clicking the Clear button.

4.2.19.1 Removing the stored Warning and Error Message Texts

Clicking the Clear button will remove all the event texts recorded in the Log Window.

It is not normally necessary to do this as the application will automatically remove the oldest records but may be useful to confirm that no new events are occurring.

4.2.20 VELOCITY PROFILES

[IEEE Command: PROS see section 5.1.22]

The velocity profiles are described in terms of maximum jerk (A), maximum acceleration (E), constant acceleration period (C) and constant velocity period (D). The 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.

Maximum Jerk, A, units: m/s

Jerk Period, B, units: s Constant acceleration period, C, units: s Constant velocity period, D, units: s Maximum acceleration, E, units: m/s

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Figure 18 Velocity Profile Elements

Note: The velocity profile has been drawn showing either constant or linearly changing velocity. It should be noted however, that during the jerk period (period of linearly increasing/decreasing acceleration) the velocity will actually be changing non-linearly. These effects are fully modelled by the GSS4100.

The profile is documented in The Standard Receiver Performance Tests, ICD-GPS-204, and 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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The four input parameters are:

Jerk amplitude (range –100 to +100m/s

Maximum acceleration (range –100 to +100m/s

), Zero Jerk is not allowed.

)

Period of constant acceleration (0 to 540 seconds)

Period of constant velocity (0 to 540 seconds)

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

The eight receiver velocity profile tests documented in The Standard Receiver Performance Tests, ICD-GPS-204 are included on the distribution diskette as read only files PROF1.DAT through to PROF8.DAT.

Note: Jerk period = (max acceleration / 10msecs)

The jerk application period must be divisible by the interrupt step size, i.e. 10ms. To ensure this case is always true the entered jerk is modified accordingly. For example a jerk value of 20 m/s

m/s

produces a jerk period of 0.775 seconds. This value is not divisible by 10ms and so the jerk period will be rounded down to 0.770 seconds and the jerk will be modified to 19.4805m/s

and acceleration of 15.5

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4.3 NAVIGATION DATA TEMPLATES

The GPS Navigation message and the Correction Data message in SBAS mode are generated from templates stored in the GSS4100 flash memory. A template is provided for each of these modes that should suffice for most test purposes. These are pre-loaded to the GSS4100 before delivery and are also provided as ASCII test files.

The GPS Navigation Message carries date and time information that increments at the 6 second GPS Epoch rate. This is inserted automatically by the GSS4100 to match the simulation time. The parity field is also computed dynamically by the GSS4100 but data other than the Epoch time remains fixed.

To allow users to adjust data fields to meet specific testing requirements there is provision for users to load a further 3 templates of each type. This may be achieved by either the IEEE.488 NSAV command or via the GUI Interface and USB.

The Templates are plain text files and may be examined and altered by any basic editor program such as Windows Notepad. Save the modified Template to the SimCHAN program folder (Typically C:\Program Files\Spirent Communications\SimCHAN). A GPS Navigation message Template must be of type *.NAV and an SBAS Correction data message of type *.WAS.

To load a Template open the Load Navigation Message Template screen from the Options Menu.

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Figure 19 Loading a Navigation Message Template

Select the type of template to be loaded, either GPS or SBAS. SimCHAN will display the Templates available in the SimCHAN folder.

Select the ID number of the GSS4100 flash memory location that will hold the Template. There are four locations numbered 0 to 3. ID number 1 is offered as the first choice to discourage you from overwriting the GSS supplied Template pre-loaded in Template number 0.

Select Load to transfer the file.

For a full description of default message parameters and how to define user *.NAV and *.WAS files see Appendices G, H and I.

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4.4 HARDWARE SETTINGS DISPLAY

Figure 20 Hardware Settings Display

This displays the Serial Number of the connected GSS4100 unit and the Versions/Release numbers of the various Firmware elements loaded into the unit. Together with this information, several hardware related parameters can be controlled and selected.

[IEEE command to check firmware version: *IDN? See 5.1.4]

4.4.1.1 Selecting the Frequency of the External Reference Signal

[IEEE Command: EREF see section 5.1.8 & EREF ? see section 5.1.9]

The GSS4100 can detect the presence of an external frequency reference signal but cannot automatically determine the frequency. The GSS4100 will automatically lock to the supplied signal but a fully stable lock is only achieved when the External Frequency is correctly declared.

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Using the mouse, click on the arrow key to bring down the list of supported external frequencies: 1, 5 and 10MHz are valid.

Click on the desired frequency to select. The GSS4100 will automatically seek phase lock with the supplied signal.

The Locked/Unlocked markers with indicate when a stable phase lock has been achieved and generally phase lock takes between 10 and 20 seconds to complete.

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

Note1: You cannot run a simulation while the reference frequency is Unlocked or attempt to phase lock during a simulation. Further to this an error will be flagged if the reference frequency becomes unlocked during a simulation.

Note2: Wait at least 15minutes after switch on before attempting external reference phase lock to allow GSS4100 10MHz OCXO to stabilise.

4.4.1.2 Enabling or Disabling the External Trigger

[IEEE Command: TRIG see section 5.1.34]

External Trigger: If the system is to be started from an external event set the required mode.

Regardless of Trigger mode the RUN button must be pressed to invoke a simulation

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). Simulation 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 Simulator is in the ARMED state. With the GSS4100 the simulator must be in the RUN state before for the Ext Trigger signal will be actioned.

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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 simulation will start and 1PPS OUT will transition high approximately 600-700nsecs after the applied External Trigger signal.

3) Delayed In this mode the GSS4100 waits for the External Trigger signal to be applied but will hold off commencing the simulation until the next internal 1PPS event occurs (‘RUN’ 1PPS event). Simulation start time is coincident with the rising edge of the 1PPS OUT signal

4.4.1.3 1PPS Output Options

[IEEE Command: TIOP see section 5.1.32 & TIOP ? see section 5.1.33]

The 1PPS Out field is used to select the signal on the rear panel connector of the same name. Options available are:

1PPS Continuously outputs 1Hz pulses with the rising edge of each

pulse coincident with the simulated GPS 1-second epoch

Gated As above but the signal is disabled before a run, so that the first

rising edge coincides with simulation time 0, start of run. Rising A single rising edge occurs at simulation time 0, start of run High Sets signal permanently high Low Sets signal permanently low

4.4.1.4 IEEE Primary Address

[IEEE Command: GPIB see section 5.1.10]

The GSS4100 will use the displayed primary address number (PAD) when operating under control of the IEEE.488 bus port at the rear of the unit.

The address may be changed by selecting the desired value, in the range 1 through 30, from the drop-down list.

4.4.1.5 Info Mask.

This is a debug facility and users should leave this on the default setting of zero.

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4.5 SYNCHRONISATION

The GSS4100 simulator incorporates a number of input and output signal ports which can be used in various ways to synchronise time between the simulator and the remainder of a user’s system. This note describes how to use the 1PPS IN and/or TRIG IN inputs to achieve synchronisation.

The GSS4100 simulator maintains time internally by means of a time counter clocked by an internal 10MHz clock. Simulations always start on a one-second rollover of this timer. The timer may be synchronised to an external system before starting a simulation by applying a rising edge to the 1PPS IN rear panel

input

. Once this has been done, simulations 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 simulation to start on the next one-second rollover of the timer. Alternatively, the user 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, whereupon the simulation starts running after a short delay. Note that the use of TRIG IN (immediate mode) together with 1PPS IN is inappropriate, as both would be attempting to control the timer, however TRIG IN (delayed mode) can be used with 1PPS IN.

If coarse synchronisation to the user’s system is sufficient, the above methods may be used with no additional considerations, however certain fixed delays, and uncertainties of the order of 100ns will exist. In order to attain precise synchronisation it is necessary to supply the unit with an external 10MHz frequency reference, and to observe certain timing requirements between the 1PPS IN and/or TRIG IN signals and the EXT REF IN signal. These requirements are detailed below.

4.5.1 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 simulation is shown in Figure 21. Provided these timing requirements are

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

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adhered to, the RF signal timing will be fixed and repeatable with respect to REF IN every time a simulation 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 a simulation is running, i.e. synchronisation can only take place whilst in the HALTED state.

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

ARMEDARMED RUNNING

Figure 21 Timing requirements for 1PPS IN and resulting start timing

4.5.2 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 10MHz clock cycles after the

It should be noted that 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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trigger is recognised before the simulation starts. This is shown in Figure 22.

XT_REF_IN_(10MHz)

thold (20 ns min)

tsetup (10ns min)

TRIG_IN

nternal_10MHz_clock

1PPS_OUT

Simulation_state

RF_State

ARMEDARMED RUNNING

Figure 22 Timing requirements for TRIG IN (Immediate Mode) and

resulting start timing

4.5.3 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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4.6 UPDATING SOFTWARE

GSS4100 Firmware updates are applied via the USB Link. A utility that performs this task is available from the Spirent Communications Support Team. It is not anticipated that users will need to change or replace Firmware elements but if this becomes necessary then the Support Team will provide full instructions and a copy of the utility as part of the update package.

To update the Firmware. Connect the unit using USB and Start the update utility.

Figure 23 Open the Update File

You will be prompted to select the file carrying the updated firmware, in this example a file of type *.bin.

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Figure 24 Firmware Ready to Load

The utility will only proceed it a recognised GSS unit is connected to the USB. The utility also checks the selected update file and displays its embedded identification string and version number.

Check that this is the Firmware you intend to install, then click the Load button. Loading the GSS4100 firmware takes ~15 seconds. The utility displays an approximate indication of progress and indicates completion by a Message.

Figure 25 Firmware Update Complete

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The Firmware will have copied to a holding area in internal memory. This will be copied to the appropriate memory location the next time that the unit is switched on.

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5 GPIB INTERFACE & COMMANDS

5.1.1 GPIB COMPLIANCE

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 GPIB serial poll register to enable the remote controller to monitor basic operation only.

5.1.2 DEFAULT GPIB ADDRESS

The GSS4100 is delivered with the IEEE.488 (GPIB) 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 GSS4100 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.

5.1.3 IEEE-488 COMMAND SET

5.1.3.1 Semantics

All messages are initiated by an ASCII character identifier such as IDEN, 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. 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).

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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 command is received.

Query responses have EOI asserted on the last byte of the response.

5.1.3.1.1 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

5.1.4 *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

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<Model> is GSS4100

<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, GSS4100,1234,1-01

5.1.5 ARMS Prepare to Run

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

The message format is:

ARMS

5.1.6 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 section 6.5.

On the GSS4100 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, see 5.1.26. An exception to the above is the external reference out of lock indication, where the LED will stop flashing and the flag in the

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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.

5.1.7 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.

5.1.8 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.

5.1.9 EREF ?

Query External Reference Frequency

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

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The message format is:

EREF ?

Example Response:

EREF 10MHz INT or

EREF 10MHz EXT UNLOCKED or

EREF 10MHz EXT LOCKED

5.1.10 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 GPIB 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.

5.1.11 HALT

Stop the Simulation

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

5.1.12 IDEN Query the Unit Configuration Details

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

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The message format is:

IDEN

Example Response:

Type GSS4100

Serial Number 0001

Firmware Issue 1.00

Motherboard Revision 1

5.1.13 IPRG

Set Initial Pseudorange

Sets the initial simulated 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

5.1.14 LEVL

Set the RF Output Power Level

Sets the power level for the simulated 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.

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5.1.15 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

5.1.16 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 a simulation run.

The message format is:

NDSW <code>

Where

<code> 0 Suppress transmission of the message

1 Transmit the message

5.1.17 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>

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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 Appendices H and I, plus the example files supplied.

5.1.18 NSAV ?

Query Navigation Template Commands the unit to return the GPS and SBAS template information.

The message format is: NSAV ?

The GSS4100 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.

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5.1.19 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.

5.1.20 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 GSS4100 these sets of parameters are incorporated in the firmware.

The parameter sets each comprise four floating-point values that together define the profile. See section 4.2.20 for 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.

5.1.21 PROF

Enable/Disable Velocity Profile

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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.

5.1.22 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/s/s

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

m/s/s

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

seconds

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

seconds

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5.1.23 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

5.1.24 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

5.1.25 RUNS

Begin Simulation

Commands the device to start running in simulation mode.

The message format is:

RUNS

5.1.26 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:

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SERR 00000001 0, Command not recognised WEAK 987

5.1.27 SG2D

Select PRN by G2 Delay

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

The simulator 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

5.1.28 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

5.1.29 SNUM ?

Query the Device Serial Number

Commands the device to return its serial number.

The message format is:

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SNUM ?

Response

An ASCII string of the form 0999.

5.1.30 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 5.3 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

5.1.31 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

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5.1.32 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 simulation is running

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

5.1.33 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

5.1.34 TRIG

Select External Trigger

Select Trigger mode. The selection determines how the device will commence a simulation 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

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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

5.1.35 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.

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5.1.36 WEEK

Select GPS Week Number

Commands the device to commence the next simulation 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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5.1.37 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

5.1.38 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 simulation 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.

5.2 COMMAND AVAILABILITY BY MODE

Some simulation information must be defined before the simulation is armed and run. Thus some commands are only available in certain modes. This is summarised in Table 1, overpage. The Controller application can determine the device's operating state via a Serial Poll. The device will regard a command received in a wrong state as an error. The Command will not be executed and an error flag will be set that can be interrogated by a Serial Poll.

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IDLE ARMED RUNNING

*IDN?

ARMS

AUXP

BITE

COSW

EREF

EREF ?

GPIB

IDEN

IPRG

LEVL

LEVL ?

NDSW

NSAV

NSAV ?

NSEL

PFIL

PROS

PRTY

RSET

SERR ?

SG2D

SIGT

SNUM ?

STAT ?

SVID

*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

TIOP

TIOP ?

TRIG

VCTY

WEEK

WRTE

ZCNT

Table 1 Commands by Mode

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5.3 SERIAL POLL – STATUS BITS

The device status is signalled by setting bits in the GPIB 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 BITE query is performed to reset the error condition. The BITE query also gives additional information on the command or parameter error, which caused the error condition.

5.4 EXAMPLE COMMAND SEQUENCES

5.4.1 EXAMPLE GPS SIMULATIONS

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 Simulation

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 Simulation

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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5.4.2 EXAMPLE WITH EXTERNAL TRIGGER

Step 1 – Basic Initialisation

RSET ;Reset Simulation

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 Simulation

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 Simulation 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

5.4.3 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 Simulation to Idle mode

RSET ;Reset Simulation

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 Simulation

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 Simulation 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

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6 HARDWARE CALIBRATION / CONFIGURATION

6.1 INTRODUCTION

The GSS4100 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.

It is recommended that these calibrations be performed yearly.

Calibration involves operating the equipment with the casing removed and mains power applied. Appropriate care must be taken. These adjustments should only be performed by a suitably skilled person.

Note: Anti-static handling precautions to be used throughout

6.2 REMOVING THE GSS4100 CASE

a) Ensure that nothing is connected to the front panel RF OUT

connector.

On the rear panel, turn off the power switch and remove the power

cord. Remove USB cable and any other connections.

c) Undo the four screws securing the rear panel bezel. These are

located near the rubber feet. Remove the bezel.

d) Undo the four screws securing the GSS4100 chassis into the case.

These are located at the four corners of the rear panel.

e) Undo the two screws on the underside of the GSS4100 case which

secure the chassis. Place unit correct way up on bench.

f) Remove the chassis horizontally from the rear of the case, avoiding

any upward force.

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The frequency and power adjustment potentiometers are located as shown in the diagram below.

6.3 FREQUENCY 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

-9

, for example an HP5065A Rubidium standard. It is permissible to use a less accurate standard if the user is prepared to accept lower frequency accuracy for the simulator.

If you have not already done so, remove the GSS4100 case as described in section 6.2

This procedure involves operating the equipment with the casing removed and mains power applied. Appropriate care must be taken!

Reconnect the power cord and attach the frequency counter to the

10MHz OUT BNC connector on the rear panel. Turn on the GSS4100.

Allow 30 minutes to 1 hour for the internal oscillator to stabilise.

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Use the frequency adjustment potentiometer to achieve a frequency reading of 10MHz ± 0.1Hz.

6.4 POWER LEVEL CALIBRATION

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

1.57542 GHz and power levels between –50dBm and –60dBm, 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.

This procedure involves operating the equipment with the casing removed and mains power applied. Appropriate care must be taken!

A utility is provided in the GSS4100 software to assist in this calibration.

If you have not already done so, remove the GSS4100 case as described in Section 6.2 and locate the Power adjustment potentiometer. Reconnect the power and the USB connector and restart the GSS4100 software on the PC.

From the Menu Bar select Options->Power Calibration and follow the onscreen prompts. The software will set up a calibration signal on the rear panel MON/CAL output and calculate and display the power level required on the power meter. Adjust the potentiometer to obtain this value ±0.05dB. The calibration is then complete.

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6.5 BITE REPORTING

BITE messages are displayed in the message window, see Appendix F. Message types “info”, “fatal” and “warning” contain information for SPIRENT use only.

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

Message type “hardware”, contains BITE information generated by the GSS4100 hardware. All hardware messages except for the following will require the user to contact SPIRENT.

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.

6.6 UPGRADING THE FIRMWARE USING THE FLASH MEMORY LOADER

The GSS4100 internal firmware may be upgraded in the field. SPIRENT may make upgrades available from time to time to customers under Warranty or a Support agreement. Upgrades will be made available via suitable media or from an FTP site.

The GSS4100 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 reprogrammable memory locations.

The boot code will always check for a new image and run it if found. If no new image is found the default image will be run.

The firmware may be upgraded in the field over the USB interface using a utility supplied by SPIRENT.

This utility is accessed from the Windows Start menu:

Start->Programs->GSS->Flash_Loader.

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Note: This utility must not be run at the same time as the main GSS4100 application.

Before running this utility ensure the GSS4100 hardware is connected and powered on.

A file selection window is displayed. Select the upgrade file supplied by SPIRENT and then click Load. A message will be displayed when the upgrade has been downloaded.

Exit the application. Power to the GSS4100 must be now be cycled. When the GSS4100 powers up again, the upgrade is complete.

The current firmware issue may be checked using the

Options->Hardware Settings menu item on the GSS4100 software, see section 4.4.

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7 CONTACTING SPIRENT

From US, Canada, Central and South America, Japan and Southeast Asia:

Global Simulation Systems Inc., 4050 Sandshell Drive, Fort Worth, Texas 76137 USA

General Enquiries. +1 (817) 847 7311 Helpline +1 (817) 847 7098 Or (877) 396 4774 toll free from the US and Canada Fax +1 (817) 847 7235

Email help@gssi-usa.com

From all other countries:

Spirent Communications Limited Aspen Way, Paignton, Devon, TQ4 7QR, England

General Enquiries +44 (0)1803 546300 Helpline +44 (0)1803 546333 Fax +44 (0)1803 546301

Email support@spirentcom.com

Or visit our website: http://www.spirentcom.com/

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A GLOSSARY

ATE Automatic Test Equipment

BPSK Binary Phase Shift Keying

C/A Coarse Acquisition

CAL Calibration

FEC Forward Error Correction

GND Ground / Earth Connection

GPS Global Positioning System

GPIB General Purpose Interface Bus

HOW Handover Word

IODP Issue of Data PRN

ISCN Intentional Satellite Clock Noise

LSB Least Significant Bit

MSB Most Significant Bit

OCXO Oven Controlled Crystal Oscillator

PRN Pseudo Random Number

rads Radians

RAM Random Access Memory

RF Radio Frequency

RMS Root Mean Square

SBAS Satellite Based Augmentation System

SV ID Satellite Vehicle Identity

TLM Telemetry Word

TOW Time of Week

UDREI User Differential Error Indicator

UTC Universal Co-ordinated Time

WAAS Wide Area Augmentation System

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B CONNECTING A GPS RECEIVER

This Appendix has been included to offer the user, new to both GPS Simulators 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.

1. An input socket for a passive antenna.

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

3. 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

ST R 45 0 0

Receiver antenna port DC & RF

If this is not available an alternative is to use the high power 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 panel is artificially high. For this reason the above arrangement may not yield an identical receiver performance.

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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 GSS4100 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 GSS4100 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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C SIGNAL GENERATOR CONNECTIVITY

PORT IN/OUT TYPE CHARACTERISTICS

Primary RF OUT

COAXIAL

Type ‘N’ Female

MON/CAL Output

OUT COAXIAL

Type ‘SMA’ Female

TRIG IN COAXIAL

BNC Socket

External Reference

IN COAXIAL

BNC Socket

10MHz OUT Internal Reference

OUT COAXIAL

BNC

Socket Oscillator IEEE-488 IN/OUT IEEE-488

connector USB IN/OUT USB

connector

Provides the primary RF GPS signal output at specified levels. 50 ohm. VSWR <1.2:1 (in band). DC isolated.

Provides a high level output suitable for calibration with a power meter. 50 ohm. VSWR <1.2:1 @ L1. DC isolated.

External Trigger input, allows external control of simulation start time. Supplied signal to have a pulse width ≥120nsecs. (See section 4.5). TTL compatible levels 50 ohm Allows the GSS4100 to be locked to an external reference. 5 or 10MHz: sine or square wave, -5 to +10 dBm 1MHz square wave, 0 to +10 dBm 50 ohm Required accuracy <0.1 ppm. 10MHz Sine 0 dBm nominal 50 ohm

Host interface. IEEE-488 (GPIB) compatible. Host interface with PC. Universal Serial Bus, bi-directional.

This table is included for reference only, MS2977, GSS4100 Product Specification should be

used as the definitive document.

DC isolation can withstand a maximum DC level of ±100V and reverse RF levels to a

maximum of 1W.

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PORT IN/OUT TYPE CHARACTERISTICS

TRIGGER IN COAXIAL

BNC Socket

Aux Output IN/OUT 25 way

D type

110/240V ac IN Industry

Standard IEC

A trigger input to allow an external signal to start the simulation. TTL level compatible 50 ohm Pin No. Signal Name

11PPS IN 2 1PPS OUT

* 3 Reserved 4 Reserved 5 Reserved 6 Reserved 7 Reserved 8C/A CLOCK* 9 CODE 1PPS* 10 C/A EPOCH* 11 NAV DATA* 12 C/A CODE* 13 NC 14 GND FOR 1PPS IN 15 GND FOR 1PPS OUT 16 NC 17 GND 18 GND 19 NC 20 NC 21 GND FOR C/A CLOCK 22 GND FOR CODE 1PPS 23 GND FOR C/A EPOCH 24 GND FOR NAV DATA 25 GND FOR C/A CODE

Notes:

Input signals marked * are 50 ohm terminated, Output signals marked * are 50 ohm drive capable. Auto-switching. No voltage selection required.

In combination with the External Reference input, can be used to

synchronise the simulator to an external system, (See section 4.5). TTL level compatible

TTL level compatible, nominal pulse width 100ms

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D SIGNAL CAPABILITY

PARAMETER COMMENT VALUE UNITS

Number of GPS

L1 1 channel signal sources In-band spectral purity (1575.42 ± 20)MHz Harmonics of L1 Referred to unmodulated

Referred to unmodulated

carrier level at RF output,

whichever value is greater

< -30

< -160

<-35 dBc

carrier Close to Carrier unmodulated phase

Integrated between 10Hz and

10kHz

< 0.02

RMS max noise (Single Sideband) Nominal signal

level Signal level control Dynamic range relative to

Signal Dynamics Maximum Relative Velocity

Main RF port CAL port (approximate)

nominal level.

Maximum Relative

-130

-70

+20, -20

0.1

±15,000

±450

Acceleration Maximum Relative Jerk Maximum Angular rate (1.5m

±500

2π

lever arm)

Nominal carrier

L1 (GPS/SBAS) 1575.42 MHz frequency Modulation C/A code ranging

(PRNs 0-1023)

GPS Data Bit Rate Channel Hardware

1.023 50

100 Hz Update Rate 1PPS Out to RF Delay

Nominal delay zero

±5

(1σ) RSS

dBc

dBm

Rad

dBm dBm

dB dB

m/s

rad/s

Mcps

Bps

nsecs

This table is included for reference only, MS2977, GSS4100 Product Specification should be

used as the definitive document.

The STR4100 provides both the normal front-panel RF output port (RF OUT) for testing, and a high-level, rear-panel output port (CAL OUT) to allow calibration. Both ports are isolated to dc voltages. Nominal corresponds to the 0dB setting of the SimCHAN Power Slider control.

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E ENVIRONMENTAL

Dimensions, nominal

Weight

Signal Generator

(approx)

Temperature

Operating Temperature Humidity

Storage Temperature Humidity

Electrical

Voltage (a.c.) Power Consumption Frequency

254mm x 345mm x 99mm (W x D x H) (10inch x 13.6inch x 3.9inch)

5kg (11lb)

+10 to + 40

C (50 to 104oF)

40 to 90% RH (non-condensing)

-40 to + 60

C (-90 to 140oF)

20 to 90% RH (non-condensing)

100 to 120V RMS, 220 to 240V RMS <70W

48 to 66 Hz

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F GSS4100 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 Table 2, overpage.

The return format is: BITE 00000010 4 - FPGA_TIMER – Invalid number of ms in second

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Table 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 GSS4100 ran out of velocity profile data. 3 EEPROM - Attempt to write to locked

EEPROM

4 FPGA_TIMER – Invalid number of ms

in second

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

6 USB – No more receive buffer

descriptors available

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

8 USB – No more transmit buffer

descriptors available

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

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.

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

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

DGP00673AAA 1.02

Bit String Description 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 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 changed during run

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

The state of the external reference changed during the

run.

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G STANDARD GPS NAVIGATION MESSAGE

G.1 INTRODUCTION

The following description details the default GPS navigation message supplied with the GSS4100.

The navigation message is constructed from 25 frames of data and has a total duration of 12.5 minutes. Each frame is made up of 5 subframes, which in turn consist of ten, thirty bit words.

For words of 3 through 10 of each subframe, it is possible to generate a representative navigation data model using stored data. The parity bits of these words may also be selected to be valid or invalid.

The format of the telemetry and handover words (words 1 and 2) does not change, and the parity bits for these words are always valid.

Parity bits are calculated to NATO STANAG 4294 draft issue 1 - equivalent to ICD_GPS_200. Where shown the parity bits are always the transmitted parity bits. The other data bits (1-24) are source data bits and as such may be inverted before transmission, dependant on the calculated parity bit 30 (transmitted) of the previous word. The source data bits of the words 1 and 3 of every subframe are never inverted before transmission because bit 30 of the previous word is always zero for these words. The data/parity bits marked ‘*’ may vary from frame to frame, and are calculated before transmission.

Time of Week and GPS Week are encoded into the transmitted message whilst the simulation is running. Week number rollovers are supported, but not ephemeris cut-overs.

Satellite health data within the navigation message is automatically calculated to reflect the selected PRN Number.

DGP00673AAA 1.02

G.1.1 TELEMETRY (TLM) WORD – ALL SUBRAMES

This is the first word in every subframe.

Bits 1 – 8 preamble

(1000 1011)

9 – 22 alternating ones and zeros

(1010 1010 1010 10)

23 – 24 reserved bits

(11)

25 – 30 parity

(calculated = 01 1001)

G.1.2 HANDOVER WORD (HOW) – ALL SUBFRAMES

This is the second word in every subframe.

The data/parity bits in this word marked ‘*’ will vary from frame to frame, according to the time of week and subframe ID at the time of transmission.

Bits 1 – 17 17 MSB’s of the TOW count

(calculated = **** **** **** *)

18 momentum/alert flag

(0)

19 synchronisation/anti-spoof flag

(0)

20 – 22 subframe ID

(calculated = 001, 010, 011, 100, or 101)

23 – 24 solved to ensure parity bits 29/30 zero

(calculated =**)

25 – 30parity

(calculated =** **00)

Contents

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G.1.3 SUBFRAME’S 1 THROUGH 3

G.1.3.1 Subframe 1 Word 3

Bits 1 – 10 week number, from main window

(calculated = **** **** *)

11 - 12 Set according to normal code on L2

(01 for P code)

13 - 16 SV accuracy

(0010)

17 – 22 SV health

(0000 00)

23 – 24 issue of data clock IODC (2 MSB’s)

(00)

25 – 30 parity

(calculated =** ****)

G.1.3.2 Subframe 1 Word 4

Bits 1 data for L2 P code flag

(1)

2 – 24 alternating ones and zeros

(010 1010 1010 1010 1010 1010)

13 - 16 SV accuracy

(0010)

25 – 30 parity

(calculated =** ****)

Contents

A.1.1.1 Subframe 1 Word 5

Bits 1 - 24 alternating ones and zeros

(1010 1010 1010 1010 1010 1010)

25 – 30 parity

(calculated =** ****)

G.1.3.3 Subframe 1 Word 6

Contents

DGP00673AAA 1.02

Bits Contents 1 - 24 alternating ones and zeros

(1010 1010 1010 1010 1010 1010)

25 – 30 parity

(calculated =** ****)

G.1.3.4 Subframe 1 Word 7

Bits

Contents

1 – 16 alternating ones and zeros

(1010 1010 1010 1010)

17 – 24 Estimated group delay t

1.863 ns (4x2

-31

(0000 0100)

25 – 30 parity

(calculated =** ****)

G.1.3.5 Subframe 1 Word 8

Bits

Contents 1 – 8 issue of data clock IODC (8 LSB’s) : issue 5

(1010 0101)

9 – 24 reference time clock t

(450x2

:2 hours into week

(0000 0001 1100 0010)

25 – 30 parity

(calculated =** ****)

G.1.3.6 Subframe 1 Word 9

Bits 1–8 clock correction coefficient f2 :166.5x10

Contents

(6x2-55 s/s2)

s/s

(0000 0110)

9–24 clock correction coefficient

(7x2

-43

s/s)

:795.8x10

(0000 0000 0000 0111)

25–30 parity

(calculated =** ****)

-15

s/s

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1.02 DGP00673AAA

G.1.3.7 Subframe 1 Word 10

Bits 1 – 22 clock correction coefficientaf0 :3.726x10-9s

Contents

-31

(8x2

(0000 0000 0000 0000 0010 00)

23 – 24 solved to ensure parity bits 29/30 zero

(calculated = **)

25 – 30 parity

(calculated =** ****)

G.1.3.8 Subframe 2 Word 3

Bits

Contents

1 – 8 issue of data ephemeris IODE : issue 5

(0000 0101)

9 – 24 C

: 281.25x10

-3

m (9x2-5m)

(0000 0000 0000 1001)

25 – 30 parity

(calculated =** ****)

G.1.3.9 Subframe 2 Word 4

Bits 1 – 16 mean motion difference from computed value

Contents

delta-n:1.137x10

-12

semicircles/s(10x2

-43

semicircles/s)

(0000 0000 0000 1010)

17 – 24 mean anomaly at reference time M

semicircles) (8 MSB’s) : 5.1223x10

(10 x 2

-9

-43

semicircles

(0000 0000)

25 – 30 parity

(calculated =** ****)

DGP00673AAA 1.02

G.1.3.10 Subframe 2 Word 5

Bits 1 – 24 mean anomaly at reference time M9(24 LSB’s)

Contents

: 5.1223x10

-9

semicircles(11x2

-31

semicircles)

(0000 0000 0000 0000 0000

1011)

25 – 30 parity

(calculated =** ****)

G.1.3.11 Subframe 2 Word 6

Bits 1 – 16 Cuc : 22.3517x10-9 rads (12x2

(0000 0000 0000 1100)

17 – 24 eccentricity e (8 MSB’s) : 1.5134x10

Contents

)

-29

rads)

-9

(13x2

(0000 0000)

25 –30 parity

(calculated =** ****)

G.1.3.12 Subframe 2 Word 7

Bits 1 – 24 eccentricity e (24 LSB’s) : 1.5134x10-9rads

Contents

-33

(13x2

rads)

(0000 0000 0000 0000 0000

1101)

25 – 30 parity

(calculated = ** ****)

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G.1.3.13 Subframe 2 Word 8

Bits 1 – 16 Cus : 26.077x10-9 rads (14x2

Contents

-29

rads)

(0000 0000 0000 1110)

17 – 24

square root of semimajor axis MSB’s) : 5153.7 m

1/2

(2702023066x2

-19 m1/2

(1010 0001)

25 –30 parity

(calculated =** ****)

G.1.3.14 Subframe 2 Word 9

Bits 1 – 24

Contents

square root of semimajor axis LSB’s) : 5153.7 m

1/2

(2702023066x2

(24

-19 m1/2

(0000 1101 1001 1001 1001

1010)

25 – 30 parity

(calculated =** ****)

G.1.3.15 Subframe 2 Word 10

Bits 1–16 reference time ephermeristoe:2 hours into

Contents

week(450x2

(0000 0001 1100 0010)

17 fit interval flag:6 hours

(1)

18–22 alternating ones and zeros

(010 10)

23–24 solved to ensure parity bits 29/30 zero

(calculated =**)

25–30 parity

(calculated =** ** 00)

)

DGP00673AAA 1.02

G.1.3.16 Subframe 3 Word 3

Bits 1 – 16 Cic : 27.94x10-9 rads

Contents

-19

(15x2

rads)

(0000 0000 0000 1111)

17 – 24

right ascension at reference timeΩ

: 7.4506x10

-9

semicircles (16x2

-31

semicircles)

(0000 0000)

25 – 30 parity

(calculated =** ****)

G.1.3.17 Subframe 3 Word 4

Bits 1 – 24

Contents

right ascension at reference timeΩ

: 7.4506x10

-9

semicircles (16x2

-31

semicircles)

(0000 0000 0001 0000)

25 - 30 parity

(calculated =** ****)

G.1.3.18 Subframe 3 Word 5

Bits 1 – 16 Cis : 31.665x10-9 rads (17x2

Contents

-29

rads)

(0000 0000 0001 0001)

17 – 24 inclination angle at reference time i

: 0.3 semicircles(644245944x2

-31

semicircles)

(0010 0110)

25 – 30 parity

(calculated =** ****)

(8 MSB’s)

(24 LSB’s)

(8 MSB’s)

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G.1.3.19 Subframe 3 Word 6

Bits

Contents

1 – 24 inclination angle at reference time io(24

LSB’s) :0.3 semicircles(644245944x2 semicircles)

(0110 0110 0110 1001 1011

1000)

25 – 30 parity

(calculated =** ****)

G.1.3.20 Subframe 3 Word 7

Bits 1 – 16 Crc : 562.5x10

Contents

-3

m (18x2-5 m)

(0000 0000 0001 0010)

17 – 24

argument of perigee ω (8 MSB’s) :0.5 semicircles (230x2

-31

semicircles)

(0100 0000)

25 – 30 parity

(calculated =** ****)

G.1.3.21 Subframe 3 Word 8

Bits 1 – 24

Contents argument of perigee ω (24 LSB’s) :0.5 semicircles (230x2

-31

semicircles)

(0000 0000 0000 0000 0000

0000)

25 – 30 parity

(calculated =** ****)

-31

G.1.3.22 Subframe 3 Word 9

Bits 1 – 24

Contents rate of right ascension Ω

semicircles/s (19x2

(0000 0000 0000 0000 0001

0011)

25 – 30 parity

(calculated =** ****)

:2.16x10

DOT

-43

semicircles/s)

DGP00673AAA 1.02

G.1.3.23 Subframe 3 Word 10

Bits

Contents 1 – 8 issue of data ephemeris IODE : issue 5

(0000 0101)

9 – 22 rate of inclination angle IDOT :2.2737x10

semicircles/s (20x2

-43

semicircles/s)

-12

(0000 0000 0101 00)

23 – 24 solved to ensure parity bits 29/30 zero (calculated =**) 25 - 30 parity

(calculated =** **00)

G.1.4 SUBFRAMES 4 AND 5

Both subframes 4 and 5 are sub-commutated 25 times each; the 25 versions of these subframes are referred to as pages 1 through 25 of each subframe; and each of these pages has a page ID number associated with it. A brief summary of the various data contained in each page of subframes 4 and 5 follows:

G.1.4.1 Subframe 4

1. Pages 1, 6, 11, 16, and 21:reserved. (page ID 57)

2. Pages 2, 3, 4, 5, 7, 8, 9, and 10:Almanac data for satellites 25 through 32,

respectively. (page ID’s 25 through 32 respectively)

3. Pages 12 and 24:reserved. (page ID 62)

4. Pages 19, 20, 22, and 23:reserved. (page ID’s 58 through 61 respectively)

5. Pages 13, 14 and 15:spares. (page ID’s 52, 53, and 54)

6. Page 17: Special messages. (page ID 55)

7. Page 18:Ionospheric and UTC data. (page ID 56)

8. Page 25:A-S flags and satellite configurations for 32 satellites plus satellite

health for satellites 25 through 32 (page ID 63)

G.1.4.2 Subframe 5

1. Pages 1 through 24:almanac data for satellites 1 through 24, respectively.

(page ID’s 1 through 24 respectively)

2. Page 25:satellite health for satellites 1 through 24. (page ID 51) For further details refer to the description given for each of the page ID’s.

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1.02 DGP00673AAA

G.1.5 PAGE ID’S 1 THROUGH 32

These pages contain almanac data and a health word for the 32 satellites. All the almanacs are identical, but the health word is all ok for the simulated satellite and all bad for the other 31 satellites. Page ID’s 1 through 24 are transmitted on pages 1 through 24 of subframe 5; and page ID’s 25 through 32 are transmitted on pages 2 through 5 and 7 through 10 of subframe 4.

G.1.5.1 Page ID’s 1 through 32 – Word 3

Bits

Contents

1 – 2 data ID : data ID two

(01)

3 – 8 Page (SV) ID : 1 to 32

(calculated = 00 0001 to 10

0000)

9 – 24 eccentricity e : 1.5134x10

-9

(rounded to 0x2

(0000 0000 0000 0000)

25 – 30 parity

(calculated =** ****)

G.1.5.2 Page ID’s 1 through 32 – Word 4

Bits 1 – 8 almanac reference time toa :8192 seconds

Contents

(2x2

seconds)

(0000 0010)

9 – 24

relative inclination angle δI : 0

(0000 0000 0000 0000)

25 – 30 parity

(calculated =** ****)

-19

)

DGP00673AAA 1.02

G.1.5.3 Page ID’s 1 through 32 – Word 5

Bits 1 – 16

Contents

rate of right ascension Ω

semicircles/s (1x2

-38

semicircles/s)

: 2.16x10

DOT

-12

(0000 0000 0000 0001)

17 – 19 SV health : all data OK if the page ID is the

same as the simulated SV and all data bad

otherwise.

(000) or (111)

20 – 24 SV health : all signals OK if data OK if the

page ID is the same as the simulated SV ID;

and all data bad otherwise.

(0 0000) or (1 1111)

25 – 30 parity

(calculated =** ****)

G.1.5.4 Page ID’s 1 through 32 – Word 6

Bits 1 – 24

Contents

square root of semimajor axis

(10554778x2

-11 m1/2

)

: 5153.7 m

(1010 0001 0000 1101 1001

1010)

25 – 30 parity

(calculated =** ****)

G.1.5.5 Page ID’s 1 through 32 – Word 7

Bits 1 – 24 right ascension at reference time Ωo :

Contents

7.4506x10

-9

semicircles (0x2

-23

semicircles)

(0000 0000 0000 0000 0000

0000)

25 – 30 parity

(calculated =** ****)

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1.02 DGP00673AAA

G.1.5.6 Page ID’s 1 through 32 – Word 8

Bits 1 – 24 argument of perigee ω :0.5 semicircles (222x2

Contents

semicircles)

(0100 0000 0000 0000 0000

0000)

25 – 30 parity

(calculated =** ****)

G.1.5.7 Page ID’s 1 through 32 – Word 9

Bits 1 – 24 mean anomaly at reference time Mo :

Contents

46.0546x10

-3

semicircles (386334x2

-23

semicircles)

(0000 0101 1110 0101 0001

1110)

25 – 30 parity

(calculated =** ****)

G.1.5.8 Page ID’s 1 through 32 – Word 10

Bits 1 – 8 clock correction coefficient af0 8 MSB’s

(0000 0000)

9 – 19 clock correction coefficient a

Contents

:3.726x10

(rounded to 0x2

-9

s (rounded to 0x2

-38

s –1)

-20

:795.8x10

-15

(0000 0000 00)

20 – 22 clock correction coefficient a

:3.726x10

-9

s (rounded to 0x2

3 LSB’s

-20

(00 0)

23 – 24 solved to ensure parity bits 29/30 zero

(calculated =**)

25 – 30 parity

(calculated =** ****)

–

DGP00673AAA 1.02

G.1.6 PAGE ID 51

This page contains health words for satellites 1 through 24. The health word for the simulated satellite is all ok, and the health words for all of the other satellites is all bad. Page ID 51 is transmitted on page 25 of subframe 5.

G.1.6.1 Page ID 51 – Word 3

Bits

Contents 1 – 2 data ID : data ID two

(01)

3 – 8 Page ID : 51

(11 0011)

9 – 16 almanac reference time t

(2x12

-12

seconds)

:8192 seconds

(0000 0010)

17 – 24 almanac reference week WN

: second week

(0000 0001)

25 – 30 parity

(calculated =** ****)

G.1.6.2 Page ID 51 – Word 4

Bits

Contents 1 – 6 Satellite health for SV 1 :All zeros if SV ID is

1, all ones otherwise

(0000 00 or 1111 11)

7 – 12 Satellite health for SV 2 : All zeros if SV ID is

2, all ones otherwise

(0000 00 or 1111 11)

13 – 18 Satellite health for SV 3 : All zeros if SV ID is

3, all ones otherwise

(0000 00 or 1111 11)

19 – 24 Satellite health for SV 4: All zeros if SV ID is

4, all ones otherwise

(0000 00 or 1111 11)

25 – 30 parity

(calculated =** ****)

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1.02 DGP00673AAA

G.1.6.3 Page ID 51 – Word 5

Bits 1 – 6 Satellite health for SV 5 : All zeros if SV is 5,

(0000 00 or 1111 11)

7 – 12 Satellite health for SV 6 : All zeros if SV ID is

(0000 00 or 1111 11)

13–18 Satellite health for SV 7 : All zeros if SV ID is

(0000 00 or 1111 11)

19–24 Satellite health for SV 8:All zeros if SV ID is

(0000 00 or 1111 11)

25–30 parity

(calculated =** ****)

G.1.6.4 Page ID 51 – Word 6

Bits 1 – 6 Satellite health for SV 9 : All zeros if SV ID is

(0000 00 or 1111 11)

7 – 12 Satellite health for SV 10 : All zeros if SV ID

(0000 00 or 1111 11)

13 – 18 Satellite health for SV 11 : All zeros if SV ID

(0000 00 or 1111 11)

19 – 24 Satellite health for SV 12:All zeros if SV ID is

(0000 00 or 1111 11)

25 – 30 parity

(calculated =** ****)

Contents

all ones otherwise

6, all ones otherwise

7, all ones otherwise

8, all ones otherwise

Contents

9, all ones otherwise

is 10, all ones otherwise

is 11, all ones otherwise

12, all ones otherwise

DGP00673AAA 1.02

G.1.6.5 Page ID 51 – Word 7

Bits 1 – 6 Satellite health for SV 13 :All zeros if SV ID

(0000 00 or 1111 11)

7 – 12 Satellite health for SV 14 :All zeros if SV ID

(0000 00 or 1111 11)

13 – 18 Satellite health for SV 15 : All zeros if SV ID

(0000 00 or 1111 11)

19 – 24 Satellite health for SV 16: All zeros if SV ID

(0000 00 or 1111 11)

25 – 30 parity

(calculated =** ****)

G.1.6.6 Page ID 51 – Word 8

Bits 1 – 6 Satellite health for SV 17:All zeros if SV ID is

(0000 00 or 1111 11)

7 – 12 Satellite health for SV 18 : All zeros if SV ID

(0000 00 or 1111 11)

13 – 18 Satellite health for SV 19 : All zeros if SV ID

(0000 00 or 1111 11)

19 – 24 Satellite health for SV 20: All zeros if SV ID

(0000 00 or 1111 11)

25 – 30 parity

(calculated =** ****)

Contents

is 13, all ones otherwise

is 14, all ones otherwise

is 15, all ones otherwise

is 16, all ones otherwise

Contents

17, all ones otherwise

is 18, all ones otherwise

is 19, all ones otherwise

is 20, all ones otherwise

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Spirent GSS4100 USER MANUAL

Specifications and Main Features

Frequently Asked Questions

User Manual