hello all, When I use the fft blcok, it seems not right. I build the test system like this: Square source -> IFFT -> FFT -> File Sink, when the input is 1, the output in the file sink is 1, and when the intput is 0, the output is random, sometimes 0, sometimes between -1 and 1. Like this: input: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 output: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 How should I do, so that the source data is the same as the sink data? Thanks. Heyutu
on 2012-11-13 16:44
on 2012-11-14 04:40
On Tue, Nov 13, 2012 at 10:43 AM, Zhiwen He <heyutu@gmail.com> wrote: > > > > > > > > > > > > > > > > > > > > 0 0 0 0 0 0 0 > > > > > 0 > 0 > 0 0 > > > > 0 > > > 0 0 0 > > > 0 0 > > Thanks. > > Heyutu > Hi Heyutu, I just tried this right now and don't have a problem. This is my full graph: sig_source (square wave) -> throttle -> stream_to_vector(fftsize) -> fft(fftsize, reverse) -> multiply_const(fftsize*[1/fftsize], fftsize) -> fft(fftsize, forward) -> vector_to_stream -> time sink Tom
Thank you very much. I have solved the problem, I find that, I didn't use the multiply_const block. But there is another question, when I see the data in Matlab with plot function, the figure before fft and after ifft is not same, there are something wrong on the position, where the valueis 0 in the square source. why? Thanks Zhiwen He
on 2012-11-20 16:48
On Wed, Nov 14, 2012 at 5:08 AM, Zhiwen He <heyutu@gmail.com> wrote: > Thank you very much. I have solved the problem, I find that, I didn't use > the multiply_const block. But there is another question, when I see the > data in Matlab with plot function, the figure before fft and after ifft is > not same, there are something wrong on the position, where the valueis 0 in > the square source. why? > > Thanks > > Zhiwen He I feel like there's a representational issue here. Why is your scale x10^9 (before the FFT) when the amplitude of the signal generator is 1? I'm also not clear what I'm looking at in the plotted figures. Can you label them? Tom
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