Chapter 11 351
GPS Modulation
Real Time GPS
Real Time GPS
This real-time personality simulates GPS satellite transmissions for single channel receiver testing. Basic
GPS signal building capabilities include:
• P code generation at 10.23 Mcps with the standard GPS 10.23 Mcps reference
• C/A code generation at 1.023 Mcps with the standard GPS 10.23 Mcps reference
• navigation data output at 50 bps using PN9, PN15, a fixed 4-bit pattern, a user-defined file, or default
data (TLM mode) for encoding with the C/A code or the C/A + P code
• three selectable ranging codes: C/A, P, or C/A+P
• satellite ID range of 1 to 32 with an additional range of 33 to 37 for other uses
• selectable data modes: Raw, Encoded, and TLM
• simulated doppler shift with a 250 kHz range
• selectable internal or external chip clock reference source
The signal generator’s pre-defined GPS signal setup includes a C/A ranging code, a satellite ID of 1, zero
doppler shift, a 10.23 Mcps reference clock, and the Raw data mode enabled, using PN9 data.
The satellite ID numbers match the pseudorandom numbers used to generate the C/A and P codes and
dictate the amount of chip delay in compliance with the GPS standards..
The following advanced features are also available:
• P code power adjustment (−40 to 0 dB)
• adjustable chip clock reference (1 kcps to 12.5 Mcps)
• selectable I/Q phase
• selectable filters and the ability to create user-defined filters
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