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GNSS Positioning Simulator: What is the 1PPS to RF Delay?

Environment/Versions
  • GSS4100 / 4200 / 5060 / 6100 / 6300 / 6560 / 6700
  • STR4500
  • STR4730 / 4750 / 4760 / 4780 / 4790
  • GSS7700 / 7730 / 7735 / 7790 / 7800 / 7900
  • GSS8000
Answer

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:

  1. 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.
     
  2. 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.
     
  3. At the time of manufacture Spirent measures the raw 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 +/- X ns.
     
  4. The exceptions to the technique described in point 3 above are simulator models = STR47xx and GSS77xx variant A (chassis' without 'ETH' rear panel ports)
        - STR47xx : 1PPS-to-RF Delay was never measured at manufacture. The delay is therefore unknown and uncompensated for. Typically, the raw 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