*** The bandwidth of the signal is 4 MHz.
Greetings, Carlos Alberto Ruiz Naranjo. Área de Aviónica y Sistemas No Tripulados/Avionics and Unmanned Systems Department Parque Tecnológico y Aeronáutico de Andalucía C/ Wilbur y Orville Wright, 17-19-21 41309 La Rinconada Sevilla (Spain) (+34) 954179002 http://www.catec.aero/ 2014-11-19 9:03 GMT+01:00 Carlos Alberto Ruiz Naranjo < carlosruiznara...@gmail.com>: > Hello! > > I have done the fractional delay block ( http://pastebin.com/cEDfTh9m ). > Have you seen some error? I have used the proposed filter in "Closed Form > Variable Fractional Time Delay Using FFT" [1][2] > This is my flowgraph: > > > > > - My signal sample rate is 10230000 samples per second and I want a > variable delay of 1ns of precision. What is the relationship between the > maximum precision of fractional delay and the length of the FFT? What is > the limit? > > - Is it a problem the fractional resampler of 1.023? Can it distort my > signal? [3] > > > Greetings, > Carlos Alberto Ruiz Naranjo. > > Área de Aviónica y Sistemas No Tripulados/Avionics and Unmanned Systems > Department > > Parque Tecnológico y Aeronáutico de Andalucía > C/ Wilbur y Orville Wright, 17-19-21 > 41309 La Rinconada > Sevilla (Spain) > (+34) 954179002 > http://www.catec.aero/ > > > > > > > [1] > https://www.deepdyve.com/lp/institute-of-electrical-and-electronics-engineers/comments-on-closed-form-variable-fractional-time-delay-using-fft-tNk7X6CH9c > [2] http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6171834 > [3] I use the fractional resampler because I can't put a sample rate of > 10230000 in the USRP block. > > > > > 2014-11-17 14:26 GMT+01:00 Marcus Müller <marcus.muel...@ettus.com>: > >> Hi Carlos, >> yes, your formular looks correct, scalar multiplication aside. >> >> Regarding your problem: >> It's not a problem, it's a feature :) >> you're using window functions in your FFT, that's what's changing your >> signal. >> The FFT is but an implementation of the DFT (discrete fourier >> transform), which is, considering the input as element of a >> n_fft-dimensional vector space, is but a base change, and thus has an >> inverse -- the IDFT (incarnated by the IFFT). >> >> what you see is something like the norm of the square of the window >> function; use "rectangular" to avoid this. >> >> Greetings, >> Marcus >> >> On 11/17/2014 12:23 PM, Carlos Alberto Ruiz Naranjo wrote: >> > I have some questions about FFT method. >> > >> > - I have done a test with my signal ( [Signal] -> [FFT] -> [IFFT] -> >> [Signal] >> > ) and I have a problem with the spectrum (central lobe): >> > >> > >> > >> > >> > >> > - To insert a delay I multiply the FFT by [1], right? >> > >> > Can I insert a delay (no variable) if I multiply the FFT by GNURadio >> sine >> > complex block? >> > >> > >> > >> > >> > Greetings, >> > Carlos Alberto Ruiz Naranjo. >> > >> > Área de Aviónica y Sistemas No Tripulados/Avionics and Unmanned Systems >> > Department >> > >> > Parque Tecnológico y Aeronáutico de Andalucía >> > C/ Wilbur y Orville Wright, 17-19-21 >> > 41309 La Rinconada >> > Sevilla (Spain) >> > (+34) 954179002 >> > http://www.catec.aero/ >> > >> > >> > [1] N: length of FFT, m: delay, k: position >> > >> > >> > >> > 2014-11-12 15:32 GMT+01:00 Marcus Müller <marcus.muel...@ettus.com>: >> > >> >> well, yes, you could, but that sounds ugly: >> >> 1. a sample rate of 1e9Hz implies --for complex float-- a memory >> >> consumption of 1e9*8B~=8GB per second... >> >> 2. unwieldy fractional resampling, because 10.23e6 and 1e9 don't have a >> >> very large common divisor; you'll be interpolating by a factor of >> 100000 >> >> just to decimate by 1023... That is effectively just very very many >> samples >> >> in-between. >> >> 3. you're sampling at 10.23MS/s, but you want to do something with a >> >> temporal resolution of 10 times that rate; that's a phase shift, for >> sure, >> >> but I'm afraid that it sounds like you're trying to harm Nyquist in >> some >> >> way or another. >> >> >> >> When were talking on how to simulate delay introduced by radar range in >> >> GNU Radio, a wise[1] elder[2] told me to do time shifting in frequency >> >> domain: >> >> >> >> The idea is that a time shift corresponds to frequency shift in >> frequency >> >> domain, so you can, within the spectral precision defined by the >> length of >> >> your DFT, have arbitrary shifts by doing [time >> signal]->[DFT]->[multiply >> >> with complex sine]->[IDFT] . Note that, due to the circular nature of >> the >> >> DFT, this will distort the first samples of the output. >> >> >> >> Greetings, >> >> Marcus >> >> >> >> [1] one might consider him wise >> >> [2] not really an elder >> >> >> >> >> >> On 11/12/2014 02:50 PM, Carlos Alberto Ruiz Naranjo wrote: >> >> >> >> Hello, >> >> >> >> I have in my project a sample rate of 10.23 million samples per second >> and >> >> I need to delay the signal +-1ns. With GNURadio block delay I can >> delay the >> >> signal 97.75ns (1 / 10,230,000 -> + - one sample). >> >> >> >> Could I use the fractional resampler block to enter a variable >> >> fractional delay? >> >> Has anyone implemented a fractional delay block? >> >> >> >> Thank you. >> >> >> >> >> >> >> >> >> >> _______________________________________________ >> >> Discuss-gnuradio mailing listDiscuss-gnuradio@gnu.orghttps:// >> lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> >> >> >> >> >> >> _______________________________________________ >> >> Discuss-gnuradio mailing list >> >> Discuss-gnuradio@gnu.org >> >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> >> >> >> >> >
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