Hi everyone! I've been using log power FFT block for signal power estimation. I've fed the output of Log Power block to my custom block in which I search for peak in power spectrum and then I sum up bins left and right from that peak until the turn is reached. C++ code for power estimation:
// move right from the max
iCount = iMax_index + 1;
while (in[iCount] < in[iCount-1])
fTotalPower += in[iCount++];
// move left from the max
iCount = iMax_index;
while (in[iCount] > in[iCount - 1])
fTotalPower += in[iCount--];
I've set the frame rate property to 10 frames per second (each 32768
samples) and I use sample rate of 200kSPS. What happens is that every
fourth power estimate sample has magnitude for about 1dB lower than the
other three. I've looked deeper into situation and I found out that every
fourth power spectrum from log power FFT block has about three of four bins
thinner signal and that's why the total magnitude of the signal is lower.
I've tried lower frame rate (2 frames per second) but situation doesn't
change.
Next I tried the FFT block instead of log power FFT and the problem
disappears. So I am guessing that there is some kind of problem in Log
Power FFT block. Has anyone experienced similar problem?
Regards,
Urban
<<attachment: samples.png>>
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