Problem with square wave

Syed Faisal Shah wrote in post #234732:

Hi fellows

We are trying to transmit and receive train of square wave over
wireless using RFX 2400. We modified the usrp_siggen.py file
accordingly to generate square wave. We used

./usrp_siggen.py -f 2450M -w 100000

Is the value with -f option correct? We assume that -f option refers
to center frequency at antenna but in an
earlier post
it was mentioned that it is the DUC frequency. Which
one is correct?

On the receiver side, we used usrp_rx_cfile.py script to write the
received signal samples on a file. The received signal does not look
like a square wave rather a sinusoid. In some cases, the sinusoid
appears to be as harmonic of the square wave, sometimes as a modulated
sinusoid.

If anyone knows the cause and solution for this problem, please guide
us.

  1. Are we missing anything here? Without communicating with USRP, we
    made sure that gr_sig_source_c.cc (underlying function that
    usrp_siggen.py calls) generates a square wave.

  2. Do we need to do anything with the USRP tune function? Can we
    specify the IF frequency at the transmitter and receiver explicitly?

  3. Or we cannot transmit/receive square wave through GNU radio. We
    understand that may be some filters on the usrp board or daughter
    board will not allow high frequency signals that will distort the
    corners of the square wave but getting only a sinusoid does not seem
    right…

  4. Our ultimate interest is not in square wave. For our purpose, we
    need to generate a shortest possible pulse, say Gaussian pulse,
    transmit it over the air and implement some ranging algorithms. We
    started with square wave and got stuck.

Any help/ideas will be highly appreciated.

Thanks

Faisal

hi,

i have the same question with square wave, have anyone idea or already
fix it?

thx

angela

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