This almost sounds like an ionosonde experiment. gerry
On Fri, Nov 13, 2020 at 12:05 PM Fabian Schwartau <fab...@opencode.eu> wrote: > Hey Hassan, > > sorry to be the "bad guy" to ask: Why not do it differently? > Honestly, I did not fully understand what your plan is, but do you know > the concept of FMCW radar? They also send a chirp, receive the echo > (which is exactly what you want to do as far as I understood) and then > you just have to multiply the received signal with the transmitted > signal (i.e., mix the signals), perform an FFT over the result and you > have your impulse response. Seems much less complex compared to your idea. > Typically you add a window function on the mixed signal (Hamming, Hann, > ...) to reduce side lobes in the time/distance domain and maybe add some > zero-padding to the end of the signal (after windowing) to increase the > sample rate in the time/distance domain. > Keep in mind that Rx and Tx need to be coherently synchronized, i.e., > when implemented in read hardware they need to (at least) share the same > reference osicalltor. > > Best regards, > Fabian > > Am 13.11.20 um 18:14 schrieb Hassan Khalili: > > Dear Gnu Radio gurus, > > > > I am trying to create a channel sounder using chirp signals where: > > > > 1) Tx side: repeatedly send chips with some guard time > > 2) Rx side: use block-wise matched filter to derive impulse response. > > > > I'm really struggling to find out if I can do this purely with Gnu Radio > > blocks (I come from a LabVIEW background). This is what I had in mind: > > 1) Tx side: Build an N-point vector (linearly increasing - one cycle of > > a triangular waveform) and feed to VCO. Concatenate with M-point zero > > vector. Repeat somehow. But I cannot find a concatenate block and I > > don't know how to create the N-point vector. > > > > 2) Rx side: Break stream into (M+N)-point vectors and correlate with > > chirp signal, use peak to adjust delay and apply matched filter. I > > cannot find a correlation block either. > > > > Any help in the right direction would be great. I cannot seem to find a > > detailed Gnu Radio tutorial and there are a lot of TODOs in the block > wikis. > > > > Kind regards, > > Hassan > > > -- Gerry Creager NSSL/CIMMS (C) 979.229.5301 <--- NOTE THAT MY OFFICE NUMBER HAS CHANGED ++++++++++++++++++++++ *The way to get started is to quit talking and begin doing.* * Walt Disney*
