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osqzss / gps-sdr-sim

Software-Defined GPS Signal Simulator
MIT License
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About the baseband I/Q data of gps-sdr-sim #173

Open cdsignal opened 5 years ago

cdsignal commented 5 years ago

Hi, All

As we know GPS L1 is BPSK modulation so I think the baseband Q channel should be always "0" ? But when I checked the Bin file which generated by the gps-sdr-sim (-b 8bit or 16bit) by using the Hex edit soft , I found the Q data is not " 0 ", So any thing I misunderstanding?

Another question is: If I use gps-sdr-sim to generate 8bit or 16bit I/Q data, does the I/Q data is the Bin file arrange as below: -b 8: 8bit I0/Q0/I1/Q1/I2/Q2.........? -b 16: 16bit I0/Q0/I1/Q1/I2/Q2.........?

Thanks a lot!

osqzss commented 5 years ago

The I/Q phase rotation is cased by the Doppler frequency shift in the carrier wave. And yes, you are correct on the I/Q data format.