Re: [Discuss-gnuradio] FFT --> IFFT

[Marcus Müller]

Hi Robert!

This is strange -- but could be explained by the fact that numerical inaccuracy 
don't allow us to *exactly* recreate all values during fft-ifft operation.
Also, make sure you use a rectangular window.

How do you know there is this very low frequency carrier? how low is it? How 
much power does it have?

Greetings
Marcus

On 11/18/2013 03:40 AM, Robert James wrote:
> When I take a signal, stream->vector-->FFT-->IFFT-->vector->stream,
> I'd expect to get the original signal back.  Instead, I'm getting
> something like the original signal, but following a very low frequency
> carrier.
>
> I thought this was due to the limits in vector size, but making this
> very high (many times the sample size and signal freq) and the problem
> continues,
>
> What's weirdest is that a low pass filter or band pass filter on the
> output don't seem to solve the problem!
>
> What is my mistake?
>
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