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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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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584 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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419 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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3answers
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FFT: Removed padded zeroes?

I have an application where I do this: DFT->Filter->IDFT on a range For computational performance I'm zero-padding my FFT to a power of two, but when I ...
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1answer
815 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
624 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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589 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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452 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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2answers
8k views

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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2answers
481 views

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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496 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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1answer
731 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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2answers
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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
560 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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Advantages/disadvantage of zero padding

I would like to know what are the advantages/disadvantage of zero padding with respect to frequency measurement and amplitude measurement
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132 views

Use Zero Padding to find hidden peaks

I know adding zeros will not increase the frequency resolution. I have couple of waveforms in time domain measured over months. I take the fft of the waveforms to find frequency components. The ...
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1answer
4k views

Is digital up and down sampling linear/causal/time-invariant?

So I am trying to determine whether the process of up sampling (zero padding) and downsampling are linear, causal and/or time-invariant. Based on some resources I found online, I am under the ...
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Merits of “Zero-Phase” Zero Padding

I understand the reasons for zero-padding a finite signal before FFT. However, I was reading this book (http://www.dsprelated.com/dspbooks/sasp/Zero_Phase_Zero_Padding.html) where the topic is Zero ...
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Implementing digital filter by padding with zeros

I am making a 9th order digital bandpass filter with lower and upper corners of 200 kHz and 40 MHz respectively. I am using this filter to filter a 1D time domain signal which is 64k samples long ...
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Autocorrelation and FFT : avoid zero-padding

Some posts evocate the computation of convolution or cross-correlation using FFT and zero-padding the temporal signal. I want to compute the autocorrelation of a 3D array using FFTW (2 dimensions are ...
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138 views

Signal Resolution

I have a question. Suppose we have a signal $x(n)$, length (samples) $N=400$ which have been sampled with $f_s=8000 \mathtt{Hz}$. Also suppose $X(k)$ - the DFT transform of this signal. How many ...
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1answer
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Why is there a difference between MATLAB's FFT of a zero-padded signal compared to the non-padded case

I created a data signal and calculated the spectrum via the fft-command in MATLAB. The data-signal itself is not periodic but it is created in a way that it can be treated as one period of a periodic ...
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1answer
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Computing Hartley transform of zero-padded signal from transform of original signal?

If I have the discrete Hartley transform of a signal of length 2n, how can I use it to efficiently obtain the discrete Hartley transform of the same signal padded to length 2n+m for some m > 0?
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FFT - Effects of Windowing,Improvisation approaches on RealTime FFT Hardware

Fore-word :Kindly Observe this question has multiple updates take the latest update as question ! here below is my 256pt FFT on an 2Khz sinusoid signal,on a fixed point DSP tms320c5515 please ignore ...
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recognizing frames as voiced/unvoiced/silence [duplicate]

i have to implement a function in matlab,for labeling silenced,voiced and unvoiced frames in signal. I mean i want to specify each frame as a voiced or unvoiced or silenced frame by using pitch ...
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1answer
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Re-implementing the “spectrogram” function from matlab

I am trying to make a spectrogram viewer without using the spectrogram command. For this purpose, I used a sin function. I broke up the input signal into 256 segments, multiplied each segment with the ...
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FFT frequency domain averaging and zero padding

I'm trying to get the average frequency response of an entire piece of audio by splitting it into segments, doing an FFT on each one, and averaging the magnitudes together. Its working great until I ...
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3answers
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Zero Padding in FFT

whats is the effect of pading zeroes to a sequence in FFT? for eg: x[n]=[2 3 4 5] corresponds to X[K]=[14 -2+2i -2 -2-2i] while x[n]=[2 3 4 5 0 0 0 0] corresponds to X[K]=[14 0.58-9.65i -2+2i -3.414+...
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1answer
749 views

Zero-Padding seems to CHANGE FFT of signal!

I am having trouble with zero-padding. As I understand it, in theory, zero-padding in the time-domain should 'sinc-interpolate' the FFT of the signal in the frequency domain. This would mean, that 1)...
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2answers
11k views

How to remove the boundary effects arising due to zero padding in scipy/numpy fft?

I have made a python code to smoothen a given signal using the Weierstrass transform, which is basically the convolution of a normalised gaussian with a signal. The code is as follows: ...
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3answers
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FFT Zero Padding - Amplitude Change

I'm just learning about Fourier Transforms and as an input I'm using a WAV file (Matlab) and taking one channel of it and performing a quick Fourier transform. I've zero padded the input, as I've been ...
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2answers
495 views

change FFT bins position

I'm sampling a signal at 44100kHz, and I have 1024 samples on which I perform an FFT. My bin resolution is therefore around 43 hz/bin, so the frequencies I get energy for are multiples of 43hz: 43Hz,...
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0answers
543 views

Estimating The Time-delay using the Phase of the Cross- Correlation function

I am relatively new to time delay estimation. I am working on a project where I am estimating the time-delay from the phase of the cross-correlation function (CCF), since it is more reliable in ...
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1answer
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Padding Images To Solve Inverse Filtering Problem?

Let's say that the point spread function, h, is known for a blurred image B. If we want to apply an inverse filtering method (eg. Direct Inverse Filtering for noiseless images, Wiener Filter, ...

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