Hi all,
Reading between lines, I think that what the original poster wants is
just to be able to compute FFTs that overlap by 1/4 of the FFT size.
So, essentially what JM suggests:
fft2=fft(x(P+1:P+Q))
fft3=fft(x(2*P+1:2*P+Q))
fft4=fft(x(3*P+1:3*P+Q))
How to do this in GNU Radio? You can "split" your stream of samples into
4 branches, and include a Delay block in each of the last 3 branches.
The delay of each of these blocks should be nfft//4, 2*nfft//4 and
3*nfft//4 respectively. Then you use 4 Stream to Vector blocks with
vector size nfft and finally the 4 FFT blocks of size nfft.
When, why and how these FFTs are executed by the GNU Radio scheduler is
probably not important for the problem at hand.
But what is the FFT length "nfft" is important. You should compute this
from your sample rate, samp_rate, and the desired FFT length in seconds
T = 0.16 seconds. With this data, nfft = samp_rate * T. Hopefully this
calculation will give you an integer (and better if it's a power of 2 or
another length which is "easy" for the FFT). If not, you should probably
do some resampling.
Best,
Daniel.
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