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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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numpy fft-how to choose time and frequency domain

I was trying to perform an inverse Fourier transform using np.fft.ifft on a set of data, but I was confused about how to create the appropriate domains. I did one example about np.fft.fft where it transforms a function from time domain to (angular)…
Sam
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Prevent Matlab from wrapping phase angles to 0-2pi in complex numbers

I'm dealing with complex numbers in Matlab and I have some problems with their angles. I have a vector of angles, Ph. Then I want to construct a vector C of complex numbers as: C=exp(j*Ph). The problem is that Ph contains negative phases because…
ignatius
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Creating audio file after doing FFT and getting Amp,Freq,Phase infos

I'm using below codes to fo FFT first and then take the first 10 bigger amplitudes of FFT and corresponding frequency and phase informations. At the end of te code, i'm trying to rebuild the original signal as much as possible but not using ifft…
BRNCBKC
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How to simulate two OFDM Users with low complexity FFT/IFFT?

I have two User one of them sending over freq (0-B] and the other transmit over (B-2B]. Both of them are using OFDM and each one has Nc subcarriers. I wanted to simulate the received signal using Matlab. One way to implement, I beleive is that I…
Vahid
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MATLAB: FFT a signal to frequency and IFFT back to time domain, not exactly the first signal

I am trying to reproduce the changes on a ~30 femtosecond laser pulse. I create and display this pulse in time just fine. Also, the fft of this pulse apperas fine on matlab (central frequency and width are very fine). But when I backtransform the…
fysikos6
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Synthesize PSD in MatLab

I want to recover a time signals from a given power spectral density, assuming a normal distribution of the original signal: PSD; % [(m/s)^2/Hz] given spectrum T = 60; % [s] length of…
djf
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I've done the same code on both MATLAB and Python, but ifft2 returns different values?

I've been trying to implement an homomorphic filter in frequency domain on both MATLAB and Python using OpenCV2 and NumPy, the MATLAB code gives the expected answer but the Python does not, the resulting image is very weird. I've tested all…
user3704916
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Spectrum of real-valued signal

As far as I know the IFFT of spectrum which amplitude part is even symmetric and phase part is odd symmetric should be real. Let's consider this example: signal_spectrum = [1 2+i 3+2*i 4+8*i 5 4-8*i 3-2*i 2-i 1]; It's clear that this spectrum…
Pawel
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Conflict in Imaginary parts after IFFT

I wanted to know the reasoning behind a conflict ONLY in imaginary parts after IFFT. For both my C/C++ implementation and Matlab implemenation I am doing the same following steps. My signal x is of dimension Mx1 and I perform an N-point FFT (where…
user1082170
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inverse FFT when only a few time points are needed

I want to do some modeling that will repeatedly call an iFFT. This will take as input a parametric model of the complex frequency response (amplitude, phase) and produce as output an impulse response. I would like to compare this to a "windowed"…
Charlie
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Cepstrum analysis: how to find quefrency step?

I'm newbie in cepstrum analysis. So that's the question. I have signal with the length 4096 and sample rate 8000 Hz. I make FFT and get the array with the length 4096*2 (2*i position is for cosinus coeff, 2*i+1 position is for sinus coeff).…
QuickNick
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FFT-IFFT. How to sum up the final signal after IFFT?

I perform FFT-IFFT in order to take out 50 Hz and its harmonics from my signal, using Matlab. For this purpose I break down my signal into windows of 1024 samples, and perform FFT on it. I do overlapping of 50% as well. After FFT is done, I take out…
Elen Che
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C# FFT Library Need to know

I am solving problem related with FFT. I am having situation like, I have to forward incoming data stream towards FFT Library function or FFT routine that can transform the time domain data to frequency domain data. Which Library in C# do I need to…
Usman
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FFT returning conjugate of true answer

I have an odd problem. Following (re: copying) from here, I've been trying to implement the Cooley–Tukey FFT algorithm for arrays with a power-of-2 size, but the answers returned from this implementation are the conjugate of the true answers. int…
pbotros1234
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inverse fourier transform FFT3W

I am using C++ function to find inverse Fourier transform. int inYSize = 170; int inXSize = 2280; float* outData = new float[inYSize*inXSize]; fftwf_plan mReverse = fftwf_plan_dft_c2r_2d(inYSize, inXSize,(fftwf_complex*)temp, outdata, …
MShah
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