# Questions tagged [ifft]

The tag has no usage guidance.

187 questions
Filter by
Sorted by
Tagged with
771 views

### Inverse Fast Fourier with overlap

I had to work with sound(denoising algorithms), when I read about an algorithm it said that we do DTSTFT(Discrete-time short-time fourier transform) we will create an overlap between each "chunk" of ...
273 views

### taking FFT from DCT

There is a speech signal, $y[n]$, in the time-domain. To take it to the frequency-domain, DCT has been got from $y[n]$ (w = dct(y) in MATLAB). After it, I applied ...
1k views

### How does MATLAB recover picture from magnitude spectrum alone?

This is the transformation I did. The code fft2() the Lena picture than ifft2() it back to the original. Add some ...
475 views

### What is the effect of the natural logarithm in the frequency domain?

I have read that taking the natural logarithm of a signal $x$ in the time domain will introduce a spectral broadening and hence "up-sampling" process before the logarithm is required. I tried to test ...
897 views

### Vibration Acceleration Analysis with FFT and inverse FFT

I've been reading time series data off of an accelerometer, and converting it to one RMS acceleration in g. The sensor works in a range of 0-6.4 kHz approximately. Ideally i would like to restrict the ...
432 views

### Efficient computation of inverse FFT of real sequence using half sized FFT or inverse FFT

The inverse FFT of a folded real sequence yields a real symmetric sequence. Are there any ways to exploit this symmetry to perform a smaller complex FFT or complex inverse FFT? Background: it's ...
849 views

### Signal reconstructed using IFFT: amplitude scale larger than input

I am trying to test reconstruction of signal from IFFT. Below is the python program. I break the signal into overlapping windows and do FFT after multiplication with window function. Then I apply IFFT ...
674 views

### Bit-reversal equivalence on IFFT (radix-2 Cooley-Tukey)

From everything that I read on the internet, I understood that when performing FFT or IFFT, one should perform bit-reversal to obtain a result in natural order (Assuming input is also in natural order)...
2k views

### Inverse Fourier transform - porting from MATLAB to Python

I am porting a script from MATLAB to Python, but I am failing when it comes to the inverse Fourier transform. The function in MATLAB (ifft) includes a 'symflag', which treats the data as conjugate ...
2k views

### How to perform 2D image rotation by FFT based image translation using matlab?

I am studying rotation using 3 translations as described in this scientific paper. According to the authors , it is possible to decompose a rotation into 3 shear translations which will be implemented ...
182 views

### Down sampling in the frequency domain

I would like to down sample a signal from it's original sampling rate of 2,000,000 samples per second to 48,000 (or 44100) starting from the output of an FFT. This FFT delivers 16384 data points (...
2k views

### Upsampling and Downsampling using IFFT and FFT

Assume in OFDM , there are N=64 subcarriers. I would like to upsample my signal by Factor 8 after IFFT and pass it through channel then downsample it by factor 8 before FFT. I can use upsample, ...
424 views

### Implementing OFDM with audio signals

I've read an interesting paper called FingerIO that transmits audio waves in OFDM, and I wanted to implement and generate sounds using MATLAB. (I am quite new to signal processing, so please ...
2k views

### Implementing Frequency Domain Convolution in MATLAB (Convolution Theorem)

I'm trying to prove convolution in time domain is same as multiplication in frequency domain but I'm not getting the same answer in matlab. Here is the code:
41 views

5k views

### Implementing inverse FFT using forward FFT

I am trying to implement an inverse FFT using the forward FFT. For clarity: Let S[t] be a signal in time, and S[w] the transformed signal. As per this site, it seems one can reverse S[w], use the ...
199 views

### How to iplement fast DCT-III (for inverse of DCT-II) using FFT or iFFT

I have to implement DCT-II and its inverse which is equivalently given by a forward DCT-III. All from real to real. I have been checking some paper where it is specified how to do it. However, I ...
269 views

### How to find correlation between 3 signals

I have 3 signals, S1 S2 S3, with a same time domain and same time steps. I'm wondering if there is any correlation between these 3 signals. more specifically I want to know if it is possible to make ...
8k views

### Delete frequency components with FFT and IFFT [duplicate]

I have a signal in Matlab defined by signal and t. As it is a noisy signal, I want to delete every component below a certain ...
1k views

### How do you save/convert an image to be in the frequency domain?

Quick Note: I don't believe this is a subjective question... however if it is I will gladly modify to be more objective In ImageJ, if I take the FFT of an image, how can I save this new frequency ...
625 views

### signal analysis and synthesis with different window length and FFT length

I'm coding an analysis/synthesis system on MATLAB. I was able to recover the original signal when the length of the window (winLen) is set equal to the length of ...
1k views

### Filter - Spatial Domain Versus Frequency Domain

Note: This is a followup question of How can I create a custom band-pass filter?. Can you explain the following python source code?. Bandpass filter bank. Suppose, I have an equation ...
266 views

### Confused about DFT symmetric behavior for real-valued signals?

I have a simple and might be a preliminary question about symmetric property of DFT of real valued signals. From definition we know, DFT coefficients of a real-valued signal is conjugate symmetric, so ...
793 views

### What would be the outcome of the convolution of two images? [closed]

Lena Mask I have written a C# code which produces the following output. Is my output correct? Am I padding in the correct way?
93 views

### Is it possible to Denormalize a matrix of complex numbers?

In this article, FFT and I-FFT are achieved as the following: FFT steps process starts with a Bitmap image. Bitmap-image to Integer-image Integer-image to Complex-image Apply Forward-FFT to Complex-...
9k views

### Is it possible to apply inverse Fourier transform (I-FFT) to the following image?

Suppose, I have this image in my hand and nothing else. Clearly, this is a Magnitude-plot of some unknown image. Is it possible to apply an Inverse Fast Fourier Transform (I-FFT) operation to recover ...
3k views

### Cross-correlation and auto-correlation of an image using $\tt fft$

I'm working on a project where I have to find the auto-correlation and cross- correlation of types of pixels in an image: I am using MATLAB and my code for the autocorrelation is: ...
2k views

### MATLAB: $\tt fft$ and $\tt ifft$ scaling

In MATLAB, the outputs of the fft and/or ifft functions often require additional processing before being considered for analysis....
4k views

### Difference between frequency sampling and windowing method

These two filter design methods seem fairly similar. Both ask to determine a frequency response and then take a inverse DFT to get the filter coefficients. So what's the difference?
1k views

### MATLAB center frequency shift

I am wondering how to shift the center frequency of the below complex data from 0, to say 20 MHz (10 MHz to 30 MHz- 20 MHz bandwidth). I tried to change the indexing of the bins but I could not get ...