Linked Questions
24 questions linked to/from What happens when N increases in N-point DFT
105
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Why should I zero-pad a signal before taking the discrete Fourier transform?
In an answer to a previous question, it was stated that one should
zero-pad the input signals (add zeros to the end so that at least half of the wave is "blank")
What's the reason for this?...
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0
votes
0
answers
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Determining minimum window length for DTFT [duplicate]
Let $x(t) = \cos(2\pi\times15t)+\cos(2\pi\times22t)+\cos(2\pi\times35t)+\cos(2\pi\times42t)$ and $\forall t\in\mathbb{R} :w(t) = 1$. We sample $x(t)$ and $w(t)$ with $F_s = 92 \ \text{Hz}$. So we ...
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10
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4
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What is Frequency Resolution?
Im trying to tackle the following problem while still not having a firm idea on what "frequency resolution" means :
Suppose we sample a continuous time signal with sampling period Ts = 1/2000, and ...
6
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2
answers
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Link between DFS, DFT, DTFT
My understanding of DFT is as follows
For a signal $x[n]$ of finite-length, the DFT is DFS of the periodic extension, $\tilde{x}[n]$, of that signal $x[n]$ and also another way to view DFT is that it’...
3
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4
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How to derive the bin width / maximum frequency of DFT/STFT
The bin width is given by the $F_s / N$ and the maximum frequency is given by $F_s / 2$ where $F_s$ is the sample rate and $N$ is the number of samples of the DFT.
Going between these is trivial, but ...
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6
votes
1
answer
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For 2D signals can it be said that the frequency response is the same as the Fourier transform?
Say I have a signal: [1, 1 , 1; 1 100 1; 1 1 1];,
I wanted its frequency response, then can I take its FFT?
Why does MATLAB have two functions to do the same ...
- 59
2
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2
answers
2k
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Relation of zero-padding and frequency resolution
Consider simple rectangular pulse and FFT of it in Python:
...
- 367
1
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3
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FFT of any sinusoidal signal -- how many point fft to take?
suppose I have to measure the DFT of an 60 hz sinusoidal signal and calculate upto 20 harmonics of this. Value of the 20th harmonic will be 20*60 = 1200 HZ. Then my sampling frequency should be >= 20*...
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0
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1
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Specific Frequency Resolution
I have an audio signal
SampleRate Fs: 44100 Hz
TotalSamples: 94144 samples
Duration t: 2.1348 s
The frequency resolution is given by ...
- 132
3
votes
3
answers
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Understanding LPC for Formant Estimation
I went through the Matlab tutorial on Formant Estimation using LPC Coefficients. Though I vaguely understand the details, it's not entirely clear why we need to do this. From http://person2.sol.lu.se/...
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0
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1
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DTFT of any finite sequence in matlab
I think freqz in a MATLAB toolbox, is the way to obtain DTFT of sequence.
freqz can calculate frequency response of:
H(z)=(Num)/...
- 363
1
vote
3
answers
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Does downsampling increase the resolution of frequencies?
I am currently working in MATLAB and had to downsample a .WAV file (I used the downsample function in MATLAB) to 44.1 kHz.
However, when I compared the two spectrograms of the original signal vs the ...
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1
vote
2
answers
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Getting the DTFT from the DFT samples
How would you get the DTFT from the DFT samples?
How will the DFT indexes map to the discrete frequency and what kind of an interpolation would be required?
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-1
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1
answer
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Computing the Power Spectrum Density (PSD) on a CSV File in Python
im quit new with signal processing and im trying to calculate the PSD of a signal im sampling. the signal is an output of a DC buck converter
this is the code im using and this is the plot im getting ...
2
votes
2
answers
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Effect of changing sample rate, window duration and zero padding on DTFT and DFT
Let $T$ be the window duration, $N$ be the DFT size, $F_s$ be the sample rate, and $F_{max}$ be the frequency of the highest bin. In the context of image below:
halving the $F_s$ (keeping $T$ ...
- 396
1
vote
2
answers
2k
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Short-time Fourier transform Tradeoffs
In the Short-time Fourier transform what are the tradeoffs between different:
window functions
window lengths
sample rates
- 396
0
votes
1
answer
1k
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FFT and number of samples relations
I am new in signal processing. I generated a signal with $f_{in}=10 \mathrm{kHz}$ and also take 64 sample from this signal after doing some process in an ADC block. I want to convert the result to the ...
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0
votes
2
answers
998
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What proportion of a padded FFT should be actual values
For a given signal, I've been told that you can pad the vector with $0$s at the end to get a larger DFT, and as a result get more precision in frequency bins.
What are the limits to this approach?
...
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3
votes
1
answer
1k
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Image zooming with Fourier transform
I want to go from this image
into this one:
So basically I need to scale the white square. The authors of the paper claim that this can be done in four steps:
zero-padding in real space (image is ...
- 131
0
votes
2
answers
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Smallest FFT buffer size given zero-padding
I am currently working on a project that involves processing an audio signal by dividing it into chunks of size B. The buffer is then zero padded to have a size of 44100 points, after which FFT is ...
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0
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1
answer
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Get all local maxima of a DFT
I'm doing a Machine Learning project that incorporates many DSP elements in feature extraction. I am looking at the STFT of a piece of audio and trying to search for specific spectral features within ...
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-4
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2
answers
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Can digital filters actually separate signals?
I've come to realize what appears to be a hard limit in convolution theorem: to avoid time-domain aliasing, we must pad the signal/filter, but the padding distorts the spectrum.
Consider a ...
- 9,262
0
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3
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What's the difference between calculating the FFT of a constant sound for 5 seconds versus every 1 second and taking the average?
I'm interested in learning the frequency spectrum of a constant sound. However, there is background noise. My plan is to record the sound for 1 second, take the FFT, and then doing this 5 times and ...
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0
votes
1
answer
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How can I do a proper FFT of an interpolated signal?
I have a signal $3.5 \cdot 10^{-5}s$ long as shown below.
It was unevenly sampled so I did cubic spine interpolation.
My signal as shown in time domain about 0.9V and 1MHz frequency.
I want to make an ...
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