# Questions tagged [fourier-transform]

The Fourier transform is a mathematical operation that decomposes a function into its constituent frequencies, known as a frequency spectrum.

1,589 questions
Filter by
Sorted by
Tagged with
40 views

### The impact on the frequency of adding zero samples and non zero samples

Can someone give me a brief explanation of what is going on in here? I struggle to understand the full differences between the impact on the frequency of added zero samples and adding samples which ...
46 views

### Cosine of amplitude 1 but GNU Radio shows FFT has amplitude > 30,000

I am doing an FFT on a cosine wave which has an amplitude of 1. The FFT is amplitude is not 1 but over 30,000. What am I missing here? It's from the GNU Radio FFT wiki page:
37 views

### Calculate displacement from acceleration signal data using Fourier transformation

I recorded acceleration data from an accelerometer attached to a vehicle, and I want to calculate displacement using the Fourier Transformation Integration method. I used software called vibration ...
82 views

### Why does MATLAB's dualtree3 function not return the lowpass subband of the imaginary tree?

MATLAB has a function named dualtree3 which computes 3-D dual-tree complex wavelet transform. This function only retains the last low-pass coefficients/subband of ...
26 views

### Adding zeroes in between the samples of a discrete frequency domain leads to both zero padding and scaling

I won’t show ALL the calculations, but I’ll describe the problem fairly enough to understand. We’ve been taught that upsampling on one domain leads to padding zeroes or added time period which is zero ...
73 views

38 views

### FFT shows systematic deviations from analytical result

I am calculating the numerical Fourier transform of an exponential decay exp(-|t|) and compare it to the analytically calculated result, a Lorentzian. I find that the numerically calculated spectrum ...
39 views

### What's the relation between frequency band of $X(j\omega)$ and $\Phi_{xx}(j\omega)$?

in which: $x_{c}(t)$ is a continuous-time signal $X(j\Omega)$ is the Fourier Transform of $x_{c}(t)$ $\Phi_{xx}(j\Omega)$ is the Power Spectrum Density of $x_{c}(t)$ which defined as Fourier ...
105 views

### How do I generate a smaller DFT result?

I have a very large input that I'm Fourier-transforming. Currently, I transform the entire signal and then downsample the result. Although the transform of the large input is expensive, my results ...
21 views

### How to sample along diagonal in 2D FFT

I aquire typically 2D time traces which I process by a 2D Fourier transform. The aquisition is done line by line. First, I let the signal evolve for t1, then an action is performed that possibly ...
30 views

### Highest frequency component in 2D Fourier transform

I was trying to understand the 2d dft(discrete Fourier transform) and discrete spatial Fourier transform (dsft) of images. But while understanding the graph i didn't understand that how come ($\pi,\pi$...
44 views

### Change FFT frequency domain values range

So, I`m currently working on program for computing spectrogram in real-time, using signal from a microphone. And now I want to add "scaling" feature, that allows to look at the spectrum more ...
169 views

### DFT and perfect reconstruction of a square wave on a digital computer

I know that in theory, when reconstructing a square wave from its Fourier coefficients, unless we have an infinite amount of them, the resulting reconstruction will have Gibbs ringing artifacts due to ...
26 views

### frequency domain representation of the doppler shift sequence

This is a bit of a weird question. I have a bunch of IQ data. Its a very big file that i cant upload on here. Im working through a few exercises trying to analyse the data. I have plotted the signal ...
33 views

### Will the phase of the reconstructed data using a single MRI k-space point show any curvature?

Some courses tell that each point in k-space (spatial-frequency domain) represents a certain stripe pattern in spatial domain. Reference: https://www.sciencedirect.com/science/article/pii/...
102 views

### Phase Spectrum in Fourier Transform

Probably a simple question to answer. I have been trying to use the fft function in MATLAB and have been succesful to get the amplitude spectrum of a known signal. But when working out the phase ...
34 views

### Can largest-triangle-three-buckets downsampling method used with fourier transformed signal?

I've been reading on the largest-triangle-three-buckets downsampling method for downsampling. Though it was originally published in the thesis "Downsampling Time Series for Visual Representation&...