# Questions tagged [dft]

The Discrete Fourier Transform (DFT) is a mapping between a finite set of discrete points in a (primal) domain (time, space) and the dual frequency domain. DFT requires an input sequence which is discrete, such as a sampling from an analogue audio signal.

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### Why doesnt DFT Padding cause sinc like features

I'm new to the land of DSP so any incorrect terms please let me know. It seems padding the time domain signal can make the magnitude spectrum look 'nicer', the fact it doesn't gain any more useful ...
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### What's Nyquist frequency in DFT?

I'm currently studying digital signal processing at university but I can't figure out what the Nyquist frequency means in the DFT coefficients, I know what the Nyquist frequency is in the sampling ...
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### How signal generation affect its spectrum

Im trying to get dft of hanning window. Im trying different methods of generating the same signal, yet im resulting with such different graph of signal spectrum. ...
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### Non-uniform FFT

I'm looking for a form of a FFT where the samples in the frequency-domain don't represent uniform spaced frequencies. What I would like to get is a frequency-domain with samples that are unevenly ...
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### Is it possible to compute a 2D-FFT if the input size is not a power of 2? [duplicate]

Let us suppose to have an image with size $28\times28$, and that we want to apply a 2D-FFT without any padding operation. Does exist any algorithm which allows to perform the 2D-DFT calculation with ...
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### Does the length of DFT points (duration of a signal) affect the "amplitude" of the power spectral density?

For example, performing a DFT on a 10-second-long and 20-second-long signal with the same sampling frequencies will change the "amplitude" of the power spectral density (PSD) at each ...
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### What are the *undesirable* effects of windowing in Fourier space?

My goal is to split a periodic signal into two (or more) signals. The first signal would contain the low-frequency information, and the later signals, the higher-frequency information. These signals ...
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### Bandwidth of an entire song

My question has to do with the difference between the frequencies of a single note, and the frequencies of an entire song. If I have a 5 second signal of the form: $x(t)=\sin(8\pi t)$, here is the ...
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### How To Calculate Length Of Sequences And A Suitable N?

I have been struggling to understand how to calculate the length of a sequence and also the minimal N to choose in order to avoid aliasing. Most sources tell me to take the (last non-zero value - ...
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### Correcting noise floor of DFT sampled signal

As mentioned in the slide below (full slides located here, starting at PDF page 29), the apparent noise floor on a DFT plot depends on the number of sample points $N$ used to calculate the DFT. The ...
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