I am transmitting and receiving from the same bladeRF board using a cable and a 20 dB attenuator.
If you see in the flowgraph I multiply by 0.3, that is specifically to prevent clipping and non-linearity. I have tried using AGC or gain of low pass filter but no success. The problem is that same flowgraph is working perfectly for BPSK and QPSK(most of the times), so I think issues with amplitude/clipping/non-linearity are ruled out. However, when I move to 8PSK and QAM, I don't get demodulated output. Any suggestions whether there are issues with flowgraph or is it some issue with hardware? On Tue, Dec 3, 2013 at 8:24 PM, Tom Rondeau <t...@trondeau.com> wrote: > On Tue, Dec 3, 2013 at 6:07 AM, kt7 <kartikset...@gmail.com> wrote: > > Just a follow up. > > I have noticed that data demodulation is intermittent, like if I execute > the > > same flowgraph a number of times sometimes I get a waveform after > > demodulation but most of the time received scope is blank. > > > > I really have no explanation for this. > > Any information regarding this would be really helpful > > > > Thanks in advance > > Are you transmitting and receiving from the same BladeRF board? That > could be problematic. Are you connecting them with a cable or using > antennas? It's quite likely that the amplitude is way off. It could > either be too much or too little for the demodulator. First, make sure > you aren't sending in data that is too large, which could cause > clipping and other non-linearities in the receiver. Second, make sure > the signal is scaled to about +/-1 before going into the QAM demod > block (by using an AGC block, for instance, or manually scaling the > gain of your low pass filter). > > Tom > -- Regards Kartik Seth
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