I got a question that maybe can be answered in this group.
Most of the SDR radio's I know are using the following steps:
1e Mix the time domain Q & I signal with a NCO to make a near to zero signal
2e Take the FFT to convert it to frequence domain
3e Filter the signal by setting most of the bins to zero (multiply by filter)
4e Take the reverse FTT to convert to time domain
5e Down sample the signal to something like 8Khz sample rate.
6e Somekind of demod.
What I like to do is take step 4 and 5 together, but can not get the code
working.
If for example the sample rate S=48KHz, FFT size N=1024 then BIN=S/N=47Hz.
Then taking the reverse FFT with N=256 will result in a signal with sample rate
S=12KHz (using the same BIN size).
That will result in a smaller FFT and no down sample, so less cpu is used.
What is wrong, the code or the idea?
Fred
PE0FKO
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