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CC1310: Fast BPSK transmit-only using the new IQ patch?

sivan_toledo
Expert 1555 points
Part Number: CC1310

Hi,

I have been interested for a while in performing high-symbol-rate BPSK transmissions (I don't need RX for this mode) with CC13XX. Existing threads in this forum suggested that BPSK is possible but only at slow symbol rates.

The new CC13X0 IQ SAmples application report (SWRA571) suggests that IQ samples can be transmitted with the same limits of 500kb/s 2GFSK.

Am I correct in assuming that this implies that I can use this mode to transmit BPSK at 500kb/s or so?

Thanks,  Sivan Toledo

  • 0
    TI__Guru**** 317180 points
    BPSK is a modulation format that is not supported by the hardware in CC1310. It is possible to "fake" BPSK by ramp up and down the PA for each bit to get a constellation that looks like BPSK. Since at least 20 -40 points are required for every bit this limits the max rate for BPSK to ~20 - 30 kbps dependent on the requirements for the shape of the sent bit.
  • 0 in reply to TER
    Expert 1555 points

    Thanks TER. I think I understand but let me make sure I do. What you're saying is that if I generate IQ samples for BPSK at say 500kb/s at keep PA power constant, it will work but with a very wide bandwidth due to the spectrum leakage during the abrupt phase changes? 

  • 0 in reply to sivan_toledo
    TI__Guru**** 317180 points
    No. To get BPSK you have to use a separate patch which ramp the PA. The IQ sample patch you are asking about send the data as GFSK.
  • 0 in reply to TER
    Expert 1555 points
    OK, I see that I really do not understand. My understanding was that the IQ samples are complex baseband samples that come from a complex IQ ADC following the downconversion from UHF. In theory, I can demodulate anything from these, FSK, AM, FM, etc. I thought that the same is true for TX samples: that they are fed to an IQ DAC and then upconverted to UHF. I understand that if the PA not linear, then the amplitude of the samples will not be correctly reflected in the RF output (so RF ramping is necessary), but I thought that both the frequency and phase would be preserved. What did I miss?
  • 0 in reply to sivan_toledo
    TI__Guru**** 317180 points
    The TX side. The modulation is done directly in the synth, no IQ DAC.
  • 0 in reply to TER
    Expert 1555 points
    Thanks TER. Understood.