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Questions tagged [ifft]

NOTE: please use the FFT tag instead. The FFT is a type of algorithm for quickly computing the Inverse Discrete Fourier Transform.

The IFFT is an FFT algorithm with some different initial permutation of data samples, and often an additional normalization, such that the algorithm computes the IDFT rather than the DFT. The FFT and IFFT are always implemented by the same code.

Related topics include , , , .

More information on the IFFT can be found in the Wikipedia article on the FFT

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Unable to successfully shift a signal in Python

I'm working with a signal right now, that after applying the transfer function should be attenuated and shifted to the right. The initial signal shows the signal assuming it's at an infinite frequency - so no attenuation or dispersive effects. …
Amelia Henkel
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inverse Fourier transform matlab gaussian

I want to make discrete transverse fourier transform for a normal gaussian but get some kind of delta function and can't understand why. I should get gaussian in the time domain as well. Here is the function: close clear clc lamda=1000:1e-2:6000;…
elis02
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JTransforms : ifft odd data

I am trying to compute the Inverse FFT, given that I want only select frequencies. Here is how I am taking the FFT: final double[] points = reader.readPoints(); final DoubleFFT_1D analyzer = new DoubleFFT_1D(points.length); final double[] fft = new…
angryip
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Error using ifft with Julia

I try to compute the inverse fourier transform of a array of coefficients using ifft with Julia. I have N complex numbers on an array organized as : Y=[Y_0,.., Y_(N-1)] representing my Fourier coefficients and by computing ifft(Y) I get the…
ChrlTsr
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Compute FFT in frequency axis when signal is in rawData in Matlab

I have a signal of frequency 10 MHz sampled at 100 MS/sec. How to compute FFT in matlab in terms of frequency when my signal is in rawData (length of this rawData is 100000), also what should be the optimum length of NFFT.(i.e., on what factor does…
Mahaveer
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Error "invalid types 'float [100][float]' for array subscript"

I have copied the whole code below and commented on the line I am getting the error. I am trying to test a iDFT algorithm I found online but I cannot get it to compile can anyone help me with the following error message when I try to…
Dinul Ahmed
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Unable to generate coefficient matrix in MATLAB

I have the following piece of code and I am trying to calculate the coefficient matrix, a_k to solve the linear system to obtain h[n], the impulse response. I am using the inverse fast Fourier transform. N = 9; % period is chosen to be 16 n =…
user2639830
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GCC-PHAT on MATLAB (still challenging)

I am trying to compute time delay estimation between two acoustic signals using GCC-PHAT on MATLAB. However, it is still challenging to code GCC-PHAT with fft/ifft, where time delay estimation is always zero. I have spent hours googling but have not…
L. Nguyen
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Scale correction for IFFT of smaller frequency space created by FFT

This might be considered a repost of this question however I am seeking a much deeper explanation on this matter and how to properly solve this problem. I want to study the PSF/SRF of a voxel in a 44x44 matrix. For that I create a matrix 100x bigger…
Andre
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numpy irfft by amplitude and phase spectrum

How to compute irfft if I have only amplitude and phase spectrum of signal? In numpy docs I've found only irfft which use fourier coefficients for this transformation.
Толкачёв Иван
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Designing a Gabor filter bank in the Fourier domain

I am trying to design a gabor filter bank in the Fourier domain using the following code in Matlab: for i=1:u for j = 1:v theta =theta_list(j); w_1_x=(centerFreq(1,i)*((m+1)/2)*cos(theta)); % size of filter and image is m-by-n …
Mahsa
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"Garbled" sound using FFTW in VST Plugin

I'm still very new to signal processing, and I wanted to create a sort of example VST plugin using FFTW (since the FFT and IFFT I found on Rosetta Code seemed to be working too slowly) that does nothing but (uselessly) apply a FFT to each input…
fakedad
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How to find the impulse response of a discrete system in matlab

I have a discrete system where the input is x_n and the output is y_n now I want to calculate the impulse response of this system, that is I want to find the output of the system when the input is [1,0,...,0]. for my example when: x_n =…
M.H
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Solving convolutions in Matlab using `conv` or `fft`

This is follow-up question to my other SO post about performing multiple convolutions like where the functions are defined in my code below. I need to rescale the result of the convolution with respect to the number of time steps in the…
Medulla Oblongata
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Filtering a sinusoidal wave with FFT

I am trying to write a code in Matlab which takes a one or sum of sinosudal waves imposed with noise and try to filter it using the following algo : first i take the input and place it in a vector then i apply fft() to that vector and abs() to…
rac cool
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