Hi,
If you want the channel impulse response you may simply perform an IFFT on
the channel frequency response estimated by the equalizer of gr-dtv/dvbt
(don't forget to "shift" it, so that it starts at 0 and ends at 2\pi). I
think this is performed by the block "Demod Reference Signals", but it does
not output the estimated channel. However, modifications should be
relatively simple once you dig a little bit into the code and understand
what you are looking for. You may look at the corresponding blocks at
gr-isdbt ("Sync and Channel Estimation") to look for ideas on how to
achieve this.
best
Federico2016-10-02 20:03 GMT-03:00 Tom Rondeau <[email protected]>: > On Sun, Oct 2, 2016 at 2:40 PM, Cinaed Simson <[email protected]> > wrote: > >> On 10/01/2016 04:46 PM, Juan Antonio wrote: >> > Hello, someone would know how to calculate the impulse response of a >> > COFDM, DVB-T channel with an SDR device? >> > >> > Thank you in advance >> > >> > >> > _______________________________________________ >> > Discuss-gnuradio mailing list >> > [email protected] >> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > >> >> An inverse DFT on a sinc function in the frequency domain yields a sine >> function in the time domain. And a DFT on the sine function in the time >> domain yields a sinc function in the frequency domain. >> > > > No, the DFT of a sine function is an impulse. More formally, a Dirac delta > function. > > The sinc function is the result of a truncated sine wave where the sine > wave is multiplied by a square wave. The DFT of a square wave is a sinc, so > with a truncated sine wave in the time domain, you are convolving a sinc > with a delta function in the frequency domain. > > Tom > > > >> I presume the "C" in COFDM means to chop up the bandwidth into carriers >> such that the sinc function in one channel hits nulls in the other >> channels. >> >> Piece of cake in theory. >> >> There's a gr-dvbt project on github >> >> https://github.com/BogdanDIA/gr-dvbt >> >> I don't know anything about it - I don't even know if it works. >> >> -- Cinaed >> > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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