Keysight E8357D/67D & E8663D PSG User’s Guide 243
GPS Modulation (Option 409)
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
1
— 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
Real Time GPS Introduction
Signal Generation Block Diagram
shows how the GPS signal is generated within the PSG. Notice that
the C/A code modulates the L-band signal using the I axis of the I/Q
modulator, and the P code modulates the L-band signal using the Q axis.
Select the data provided by the data generator using the
Data
softkey or by
choosing the TLM data mode.
1. P code signals are spectrally correct but do not contain valid data.
