Adjusting Si5338 phase on the fly

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staticfloat
Posts: 5
Joined: Sun Dec 20, 2015 2:26 pm

Adjusting Si5338 phase on the fly

Post by staticfloat » Sun Dec 20, 2015 2:56 pm

Hello there, I would like to experiment with strobe-sampled radar with the BladeRF; essentially, by transmitting the same pulse, and then sampling the return pulses at slightly different phase offsets, I aim to reconstruct a signal with an effective sampling rate much higher than the actual sampling rate of the ADC. My plan is to transmit radar pulses with a stable Tx clock from the Si5338 (e.g. leave LMS_TX_CLK constant), and then increment the phase offset of LMS_RX_CLK for each pulse I transmit. (This is, of course, assuming that the targets in my radar scene stay relatively motionless as I change the phase of the clock).

I have never modified the hardware or software of the bladeRF before; is this modification something that would be relatively simple to do? I imagine I could hack together some FPGA nonsense to get this working, but I wanted to ask ya'll your opinion on how reasonable this is (from the implementation side of things; I'm pretty confident on the underlying theory), and whether this kind of operation is already partially implemented somewhere else.

bpadalino
Posts: 303
Joined: Mon Mar 04, 2013 4:53 pm

Re: Adjusting Si5338 phase on the fly

Post by bpadalino » Mon Dec 21, 2015 7:13 am

Take a look at the Si5338 Reference Manual, specifically at section 7 regarding the initial phase offset and the phase step size, and then about the registers which control stepping the phase increment.

All of these can be talked to using the bladerf_si5338_read() and bladerf_si5338_write() functions in the low-level part of the API.

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