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1 vote

Why are my frequency bins oscillating?

The idea that you're looking for here is spectral leakage. As alluded to in the comments, the DFT bins will undergo different amounts of spectral leakage depending on the initial phase of the tone ...
Baddioes's user avatar
  • 548
4 votes

Polyphase FFT example implementation

If you only have N points you cannot do better than an N point FFT does. What the polyphase does is to collect more data ...
Bob's user avatar
  • 2,243
1 vote

do closer peaks Leak more to each other (spectral leakage in FFT)

It's not exactly leakage. If the frequency of interest contains an integer number of cycles, its peak lands right on one of the frequency domain samples, and its nulls land on the others, creating an ...
Cristobol Polychronopolis's user avatar
1 vote

do closer peaks Leak more to each other (spectral leakage in FFT)

Sort of. The leakage has the shape of a Dirichlet Kernel. This similar to a sinc shape so the leakage diminishes with distance. However there is a significant fine structure so it's not monotonic.
Hilmar's user avatar
  • 44k
2 votes
Accepted

FIR filter insufficient stopband attenuation

I was trying to reproduce, but didn't see the errors. Let's take a look at the filtered waveform We see the shape as expected but there are bunch of spikes in there. These spikes are due to the ...
Hilmar's user avatar
  • 44k
0 votes

How do I isolate a part of this signal in time-domain in Matlab?

Here is what I would do: The reflection is "riding" on top of what looks like an exponential decay I would try to roughly model this decay either exponentially or as a low-order polynomial (...
Hilmar's user avatar
  • 44k
2 votes

FIR filter insufficient stopband attenuation

I'm still not 100% clear but have a good idea of what's going on. I discovered that the problem lies with the test signals. These are on the following frequencies in the -16kHz to +16kHz range: ...
Deepstop's user avatar
  • 153
0 votes

Is there a FFT algorithm which is both in-place and constant geometry?

An in-place NTT is one where the butterflies operate on the data and return it to the place it was. A constant-geometry NTT is one where the butterflies access data in the same pattern and then the ...
therealmarauder's user avatar
0 votes

Strange spectra of different volume sines

This definitively was a problem with my scaling! Before the AGC I had added a pre-downscale which caused a need for up or downscale in the AGC which then got wrong, because I hadn't done the upscale ...
Øyvind Teig's user avatar

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