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Spirent KB Article
Doc ID: FAQ11365
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GNSS Positioning Simulator: What is the 1PPS to RF Delay?
GSS4100 / 4200 / 5060 / 6100 / 6300 / 6560 / 6700
STR4730 / 4750 / 4760 / 4780 / 4790
GSS7700 / 7730 / 7735 / 7790 / 7800 / 7900
The specified range is specific to each type of simulator, as follows:-
GSS4100 / 4200 / 6100 / 6300 / 6560 / 6700 & STR4500 models = 0ns ± 5ns
STR4730 / 4750 / 4760 / 4780 / 4790 = not measured and not compensated for. Raw delay expected to be ~100ns
GSS7700 variant A = measured but not compensated for. Label attached to chassis side panel
GSS7700 / 7730 / 7735 / 7790 variant B = 0ns ± 2ns
GSS7800 / 7900 = 0ns ± 2ns
GSS8000 = 0ns ± 2ns
ADDITIONAL COMMENTS / NOTES:
You will see on some GNSS product datasheets a reference to the "Inter-carrier Bias" rather than "1PPS-to-RF Delay".
- Inter-carrier bias is directly controlled by the technique of aligning all RF carrier frequencies to the 1PPS signal and thus the same range applies.
1PPS-to-RF Delay is the timing uncertainty between a rising edge on the 1PPS output port (TIMER port) of the simulator and the corresponding event on the RF signal.
At the time of manufacture Spirent measures the
1PPS-to-RF delay for each unit and programmes this value back into the simulator such that under normal operation the actual 1PPS-to-RF delay is effectively cancelled out, i.e. is 0ns +/-
The exceptions to the technique described in point 3 above are simulator models = STR47xx and GSS77xx variant A (chassis'
'ETH' rear panel ports)
- STR47xx : 1PPS-to-RF Delay was never measured at manufacture. The delay is therefore unknown and uncompensated for. Typically, the
delay is expected to be ~100ns.
- GSS77xx variant A : 1PPS-to-RF Delay was measured at manufacture and recorded on a label on the side of the unit. The delay was not programmed to the simulator. The user must manually account for the delay.
Product : Calibration,STR4500,GSS4100,GSS4200,GSS6100,GSS6300,GSS6560,GSS6700,STR4790,STR4780