Questions tagged [zero-padding]

Zero padding consists of extending a signal (or spectrum) with zeros to extend its time (or frequency band) limits.

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Alternative Methods to Zero Padding

When using a sequential neural network to classify signals with their frequency spectrum, we would need to normalize the length of the signals to perform vectorization. The only method I'm aware at ...
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Zero-padding or Interpolation in 3D FFT

I'm trying to perform a FFT of a 3D regular grid and then compute the bin average (in spherical shell bins) of the Fourier transformed grid. The problem is that the resulted vector is very noisy as I'...
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How to optimize padding and truncating of signal

I 6000 signals that vary between 3000 and 30000 in length In the figure under you can see that most of the signals are of length 5000. So I decided to pad and truncate all signals to 10000 and feed ...
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1answer
41 views

Is zero-padding necessary for speech processing to satisfy linear convolution property?

In the FFT domain, for example, if I multiply a noise reduction gain to the noisy signal, $ Y(w)H(w) $, this translates to a circular convolution in the time domain of the same length $ y(t) \...
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1answer
68 views

FIR Filter implementation without padding

Is it possible to implement FIR filtering action without padding the input and coefficients? i.e. Let's say if the input and filter coefficients are of size 4, then the output will be 7 samples. So, ...
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how I can use the FFT data to compute the convolution?

First,I have a vector A of length N,through process ...
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79 views

Correct way of zero padding in time domain

I am very new to signal processing and want to learn the correct way of zero padding for 'n' even and odd input signals. For example, $N=6\;\&\;M=32$ $x(n)=[a, b, c, d, e, f]\;\;\;n=0,1,\dots,N-...
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Zero padding in frequency domain, any tricks to speedup?

there are many situations when one has to carry some operations on spectra, like splitting a spectrum Z wide in two Z/2 spectra, or vice versa merging two Z sized spectra in a 2Z sized one. The only ...
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102 views

Why padding zeros in the middle of a DFT spectrum improves original signal reconstruction?

I'm experimenting with the Inverse Discrete Fourier Transform. Starting from the two-cycles continuous $x(t)$ signal below: I have the discrete signal $x(n) = \{ 1, 0, -1, 0, 1, 0, -1, 0 \}$ leading ...
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Cepstrum calculation with 5-smoothing zero padding

I am trying to compute cepstrum of a signal x An implementation of this in python is: ...
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1answer
74 views

Frequency estimation of circularly shifted single tone signal

I have a discrete signal $y[n] = <e^{j ~ 2 \pi f ~ n}>_J + ~w[n]$ with $n \in [0, N[$ and $w[n]$ AWGN, $<x[n]>_K$ denotes the signal $x[n]$ circularly shifted by $K$ samples. Let's define $...
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772 views

Frequency Domain Interpolation: Convolution with Sinc Function

I am reading a paper, and I came across the following definition of sinc interpolation. Warning. I don't have a strong background in signal processing. Also, I have no clue what that bar on $\bar{F}$ ...
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Matlab: Different 1-D FFT results with and without zero-padded

Recently I am implementing FFT with C code. So I use Matlab for algorithm verification. As Radix-2 FFT was chosen, I've learned that zero-padding technique could help to reach 2^N limitation without ...
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How Much Zero Padding Do We Need to Perform Filtering in the Fourier Domain?

Consider an $M\times N$ image $f$ and an $G \times K$ filter $h$. Given that convolution in the spatial domain corresponds to multiplication in the Fourier domain, then we can perform a convolution of ...
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Is there a rule of thumb for zero padding in image processing?

I see there are a lot of answers on why zero padding is necessary and how it avoids wrapping around the sides of images. However is there a rule of thumb on how much padding will be good for the image ...
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DFT zero-padding of signals starting before n=0

If a signal starts before n=0, what part of the signal should be used to compute DFT after zero-padding? For example, x(n) = {1, 2, 3, 4, 5}, where x(-2) = 1 and x(0) = 3. If this signal is zero-...
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429 views

Zero-padding, energy conservation

When calculating the FT of a signal, and the FT of that same signal but after having applied zero-padding to it, should't the amplitudes of the FT of the zero-padded signal decrease with respect to ...
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1answer
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DFT of sum of sinusoids with random zeroed samples

I have a noisy signal consists of sum of sinusoids, I had a situation where some of the time domain samples are zeroed randomly. The following figure shows the DFT before and after zeroing, the number ...
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1answer
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Is it possible to zero-pad series when using MSCOHERE in matlab?

The function fft allows one to zero-pad, and mscohere, after all works with auto and cross spectra, which, presumably, have all been calculated with fft. I haven't found any mention on zero-padding in ...
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1answer
354 views

zero padding shifting signal peak?

I am trying to find the fundamental frequency of a low-frequency signal. I need an estimate that is precise to .01 Hz based on only a few cycles, so I'm trying to code up a fft in Python. The signal ...
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4answers
988 views

How do I calculate peak amplitude of the signal components after zero padding and FFT?

I am learning about DFT and trying to apply it to some audio processing. I am new to DSP but experienced in programming and have some background in math and physics. The FFT algorithm I use (lomontFFT)...
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1answer
137 views

Zero padding issue - cut the buffer

I have some issue with zero padding. It's probably because I don't understand it enough. I have buffer size set to 400. And I use radix-2 fft. So I take the input signal 400 samples, and add to them ...
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Windowing a signal by using Hanning / Hamming or… zero padding?

My question is about the use of Hanning or Hamming windows versus "square" windows. In my understanding, I will use a Hanning or Hamming window to limit the spectral leakage. But, on the second hand, ...
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How to increase the spectral resolution?

My question is about the spectral resolution of a discrete signal. Each sample of my signal is made up with 2^n frames sampled at 44.1 kHz. So, when I want to know the spectral resolution, I ...
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1answer
337 views

Zero padding effect on a FFT of gaussian noise

I have a gaussian noise $\nu(t)$ with variance $\sigma^2$. After a FFT I get $X(\omega)$. If now I do the IFFT on the $X(\omega)$ can I say that the result is still a gaussian noise of variance $\...
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When Is a Power of 2 FFT Slower than Smaller Sized Non Power of 2 FFT in MATLAB

Knowing that computing an FFT is faster if the amount of samples is a power of 2 I have always tried to pad the inputs to Matlab's FFT with zeros until the next power of 2 is achieved. Matlab's ...
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1answer
555 views

What does it mean when you zero pad data and why does one do it? [duplicate]

I am struggling to understand what effect zero padding data would have on EMG data. How does it improve the signals? Any help in simple terms that's not too mathematical would be greatly appreciated!
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Zero padding - High amplitude

I have a set of 512 samples that I have collected with a sensor. I'd like to apply zero padding to it, for better frequency bin resolution. However, all the tutorials I see to make this occur center ...
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1answer
207 views

Is image padding really necessary while using a filter?

I do know that we must pad an image while using a filter. But what I am suggesting is that is it really necessary? Can't we just calculate at run time if the current cell/pixel is an edge cell/pixel ...
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3answers
416 views

Spectral window when FFT is not a power of 2

I am trying to better understand zero padding and the FFT. To do so, I am attempting to plot the spectrum of the Hann window function, i.e. $$ w(n) = \frac{1}{2}\left(1-\cos\left(\frac{2\pi (n+1/2)}{...
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606 views

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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What happens when N increases in N-point DFT [duplicate]

I am curious about DFT, and I wrote a simple MATLAB code to test what happens when $N$ increases. I took a rectangular signal with length $L=15$, an then found th DFT of 16, 32 and 64 points. I looked ...
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815 views

How to perform zero-padding to 3 dimensional array

Consider an array with $t=10000$ rows, $i=2$ columns and $n=41$ as a 3rd dimension. Now I add the columns of this array to yield a matrix with $t$ rows and $n$ columns. However in MATLAB the size of ...
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592 views

remove zero padding effect crosscorrealation

I am trying to make the cross correlation on the frequency domain and I use the fft function which takes power of 2 input data so I must pad with zero my incoming sample signal and localy generated ...
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1answer
527 views

Does Zero Padding Work as Advertised?

I have trouble accepting the merits of zero padding in the frequency domain to give more points in FFT. Wonder if anyone else has similar thoughts. The mathematical 'proof'for the validity of zero ...
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How does zero-padding affect the magnitude of the DFT?

Let's simulate sinusoids of two frequencies using the following Matlab code: ...
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770 views

Filter and crop an image

I am a big fan of fft convolution. So, I mostly try to avoid non-fft convolution. Suppose, I am trying to convolute an image with another image. Suppose the first image is $512\times 512$, and, the ...
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2answers
563 views

Zero-padding a spectrum, how to split the middle bin?

When a complex digital signal is converted to its spectrum through an FFT, the result will contain a series op positive and negative frequencies. That is, when the spectrum has N bins. Bin 0 will be ...
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1answer
516 views

Zeropadding and amplitude scaling

Could somebody tell me what is the DFT scaling of a $N$-length signal which is padded with $M$ zeros ? Is it $1/(M+N)$ or $1/N$, i.e. $$ Y_k=\frac{1}{N}\sum_{n=0}^{N-1}y(n)e^{\frac{2\pi nk}{(M+N)}} \...
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1answer
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Difference Between `fft(signal, nfft)` and `fft(signal)`

I want to know the difference between these following commands (matlab) and why I get two different outputs? fft(signal); fft(signal, nfft); I found that ...
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Relationship between z-transform and DFT

I'm studying for a Signals Processing exam and came across an exercise that I'm finding pretty difficult to solve. It says: Asume there is a signal $x[n]$ of length $N$. Its $\mathcal{Z}$-Transform ...
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FFT, padding, IFFT and plot in time domain

I performed an FFT with some zero padding and would like to transform it back to time domain. When I plot the signal it looks wrong. Is it because of the padding used in the FFT? How can I make it ...
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When I ask Matlab for a zero-padded FFT, does it (or FFTW) ever explicitly create a zero-padded input vector?

If I have a length $N$ signal and ask Matlab for an $M$-point FFT, $M \gg N$, of course the computer has to allocate memory for $M$ output samples, but my question is if it ever has to allocate memory ...
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1answer
481 views

Frequency response and impulse response of black box

I am trying to find out the transfer function of a real life continuous-time black box. First thought is of course to input a delta and get the impulse response as the books have taught us but I ...
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667 views

How can I increase image size by zero padding?

For increasing the image size from 8X8 to 32X32, I tried to do zero padding. The simplest concept of zero padding in Java for me seems to be the code as shown below in Java such that I can shift each ...
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432 views

correct way for Zero padding

I am doing simulation of FMCW radar. I am applying signal processing chain on raw radar data. Here in the code below, I am taking fft of data and plotting it. ...
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2k views

How to perform a time domain shift in the frequency domain without zero padding

Apologies in advance if my question doesn't make sense. I'm not the most fluent person in signal processing. I have an array of time domain values that I would like to apply a time delay to by ...
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1answer
554 views

Why is the magnitude of the second component of my FFT spectrum always the largest one?

While working with FFT, I have a strange case with a current experimental setup. I am working with beat frequencies (intermediate frequency output) and using a standard FFT algorithm (complex to ...
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1answer
401 views

FFT peak estimation: Zero-padding vs signal repetitioon

I am working on obtaining the vortex shedding frequencies behind a 2D square using CFD. Time-varying data is being extracted from a specific cell behind the square. I've written a little python script ...
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1answer
651 views

FFT of signal with starting value zeros

I have a signal, ...