Iâ€™m attempting and failing to use a USRP2 w/RFX1800 to transmit a known
good L1 GPS signal sample to a COTS receiver for some repeatable
testing work. The code transmits without error messages however the
receiver doesn’t â€œtrackâ€ any satellites from a cold start with a sample
sufficient length and Iâ€™m not sure exactly what Iâ€™m doing incorrectly so
Iâ€™ll document what Iâ€™ve done so far in hopes that someone will point out
something obvious to persons with more DSP background than myself.
Input Sample (simple amplitude IF @ 5Msamples/sec and a IF frequency of
I convert this to a complex sample file using some C code setting Q to 0
all samples and scaling I from a signed char (-127:128) to a float
I then build a basic flow in python from the sample file to a USRP2 sink
setting the center frequency CF to 1.57542G, and a interpolation of 20
convert the 5Msamp/sec to 100Msamp/sec. The waveform transmits for the
expected 60 sec.
Do I need to offset the CF to compensate for the IF being @ 1.25Mhz
than baseband? Any other areas of gotchas, filters etc that a DSP noob
Thank you in advance.