# Questions tagged [frequency-domain]

The tag has no usage guidance.

258 questions
Filter by
Sorted by
Tagged with
79 views

### How do I warp a 1 dimensional signal in frequency domain?

I want to implement VTLN (Vocal Tract Length Normalization). It is equivalent to warping the signal in the frequency domain according to the following graph. I can't wrap my head around how one ...
377 views

### Visualising OFDM subcarriers in the frequency domain

Im struggling to understand why in some images the frequency domain shows clear bars with amplitude and phase and with 0 frequency variation (it is clear that the frequency of the waves does not ...
311 views

### Interpretation of a sampled signal in the frequency domain

Suppose we have a signal $y(t)$. For sampling we use a Dirac $\delta$ function. The sampled function is $\widetilde{y}(t)$. So $$\widetilde{y}(t) = y(t)\cdot\sum_{n=-\infty}^{\infty}\delta(t-nT).$$ ...
2k views

### Applying Gaussian Blur in Frequency Domain

Please see second update I'm trying to implement gaussian blur in frequency domain using c#. Those are steps that I'm doing: Load bitmap. Split bitmap into separate color channels. Convert every ...
3k views

### Using only positive frequencies in fourier domain, How will it affect the ifft?

I am going to do some kind of transformation and transform a data to another domain, and again back to the first domain. For this, I take a fourier transform of the data and separate the positive part ...
364 views

### Convolution theorem

As stated by the convolution theorem, a convolution in spatial domain is equivalent to a multiplication in the frequency domain.Nevertheless, when should the first be preferred over the latter?
781 views

### Examples of Causal and Complex Wavelets?

I'm looking for wavelets that are both: causal (a wavelet coefficient $W(j,k)$, where $j$ is scale and $k$ is translation, does not use data from $t > k$ to be estimated). complex (such as the ...
63 views

### Steady state variance of a stochastic differential equation - relation between the frequency and time domains

Consider a stochastic differential equation: $$dx(t) = a x(t)dt + b y(t)dt \quad (1)$$ where $y(t)$ is a stochastic process satisfying $\langle y(t)y(t')\rangle = \delta(t-t')$. We will assume that ...
36 views

321 views

### Standard deviation of Gaussian corresponding to perfect low pass filter [1,1]

For a time discrete signal, the rect-filter (for 1D signal [1,1]) is a perfect low pass filter. I was wondering, what is the best gaussian approximation of this filter? For a current problem, I ...
373 views

### How to do image reconstruction from array data?

i have 15 set of data which is the s-parameter, consist of 2 column (1001x2) each set. The first column is frequency and the second column is magnitude in dB. I have transform the magnitude from (dB) ...
151 views

### What features to use for multilayer perceptron model of an EEG signal?

I have an EEG signal that I want to extract features to apply multilayer perceptron (MLP). What I should use, Fourier or wavelet coefficients?
1k views

### Fractional Frequency and negative Frequencies

So, when we Sampled any signal at the rate lower than Nyquist Frequency we get aliasing, for instance, If the frequency of Cosine wave is 5Hertz and I had to make 5cycles in a second and if the ...
39 views

### Train of impulses in frequency domain

Why compressing a train of impulses in time domain produce a wide-spaced train of impulses in frequency domain and vice versa? i want to know the intuition behind that.
19 views

### The best method to convert piano sound to music notes in real time [duplicate]

I was looking for a way to convert piano sounds to piano notes for my research. I discovered the conversion of piano sound to piano notes using FFT and piano note recognition using CQT. I am also a ...
79 views

### Sweep synthesis in frequency domain: How to correctly adjust magnitude?

I'm attempting to synthesize a logarithmic sweep signal to measure the IR of a system. For the most part, I'm following Section 5.2 of the paper Transfer Function Measurement with Sweeps. To generate ...
37 views

### How to downsample a fourier transformed signal?

I have a signal of length 100000 timestamps sampled at a frequency of 25kHz. First I apply a high pass filtering at (300Hz) and then do the Fast Fourier Transformation. Then the absolute values are ...
64 views

### Digital filtering based on frequency component amplitude… why not?

I've got a very general question. I've just implemented a filter working in frequency domain that simply cuts every frequency component whose modulus amplitude falls below a certain threshold value. ...
125 views

### Why does this transfer function estimation not work? System identification

Goal: I have an unknow dynmical system $G(s)$ and I want to find it from measurement data, output $y(t)$ and input $u(t)$. The data is frequency responses. Method: I begun first with creating the ...
189 views

### Break a signal into segments, add them together and then perform an FFT on the result

If you break a 4 second signal into 0.5 second segments, add them together and then perform an FFT on the resultant 0.5 second data. Will the FFT / frequency spectrum be the simlar to an FFT on the ...
3k views

### Simulation of FMCW radar in frequency domain

I would like to simulate a FMCW radar in the frequency domain. I used the code (Matlab) I attached below. Specially I am interested in the phase spectrum of the beat signal. In a further research I ...
39 views

### How to conserve symmetry of discrete spectrum after applying fractional delay in the frequency-domain? [duplicate]

Imagine a real-valued, discrete-time signal $h[n]$ with $N$ samples and a sampling period of $T_s = 1/f_s$. We know that the DFT of the signal $H[k]$ is conjugate symmetric because the signal is real-...
2k views

### Equalize Speaker using Frequency Response Curve

I have a speaker for which I know the frequency response curve (-5dB at 600Hz, -3dB at 700Hz, ... +5dB at 10kHz). This response curve is not as flat as I would like, and so I want to write a script ...
1k views

### Why do we need a Homomorphic Filter?

Please, explain in layman's terms, Why do we need a Homomorphic Filter? In what kind of situations should we use Homomorphic filtering? What kind of images need Homomorphic filtering?
537 views

### How to convert a spatial frequency in a 2D-DFT into the units radians per pixel?

Let's say I have a 2D image, and I take the discrete Fourier Transform (via FFT) of that image. In the frequency domain, I get the following image: In this image, let's just assume all the spatial ...
225 views

### How do I find amplitude modulation effects in natural signals

It is relatively easy to discover overlaid (additive) signals in natural phenomena using wavelet decomposition, Fourier Transforms, CEEMD, etc, because addition in the time domain is the same as ...
147 views

### Does MATLAB have a FM discriminator [closed]

I'm wondering if MATLAB communications or DSP toolboxes has a FM discriminator? If so, what is the name of the function/object?
1k views

### Envelope detection in frequency domain with MATLAB

I need to compute the envelope of a spectrum in MATLAB. Is there a specific function that can do it? I saw the function [yupper,ylower] = envelope(x,np,'peak') ...
82 views

### Comparing the spatial frequency between groups of images

I have 2 groups of images, and I want to compare these groups based on the spatial frequencies of the images. In the end, I'd like to be able to say "group A is/is not significantly different from ...
138 views

### Creating synthetic frequency domain box filter vs 4 pixels in corners

Creating two 10x10 black images. 1st image, adding a 2x2 white box in the middle (Low pass filter). 2nd image, adding 1 pixel in each of the corners. Then performing the following steps in that order:...
338 views

### Why does my overlap-add integrator in frequency domain result in distorted signals?

With help from the dsp guide and DSP-Related, I tried to implement a leaky integrator in octave/matlab. It seems to work in general, but there are a few problems. So that's what I do: Calculate the ...
105 views

### question about the frequency of Gabor filters

The Fourier transform of 2D Gabor filters is shown below: F is the radial frequency of the Gabor functions. Another parameter Fm is denoted as highest central frequency. Fr is the constant frequency ...
799 views

### Adding shot noise in frequency domain

I have a current signal represented by an array in python, which I would like to add shot noise to. Shot noise is defined as $$σ_i = \sqrt{2qI \Delta f}$$ where $q$ is the elementary charge, $I$ ...
110 views

### How to optimize a wavelet transform?

I am using complex morlet wavelet to estimate frequencies and damping ratios in a 1-D signal. I have done it so far, and the results are accurate enough. Now my question is how can I modify or ...
870 views

### adaptive filter does not converge for all inputs

I am trying to make a frequency domain adaptive filter in matlab. It uses matlab adaptfilt.fdaf to create the filter parameters like step size and initializing initial filter weight values. Then I ...
89 views

### Keep the exact frequency content - Multidimensional fft

In Matlab I've got to generate a Gaussian process embodying a certain frequency content. Not to go multidimensional, I have used reshape function. I explain better ...
161 views

### Where do harmonics come from?

At first, I thought harmonics come from the signal being periodic. However, we know a sine wave is also periodic but contains a single frequency and no harmonics. A harmonic for me is a component (...
282 views

### How to effectively teach topic of frequency domain?

This is a soft question. The frequency domain has made revolution in the field of Mathematics, Digital Signal and Image Processing etc. Some of concepts which are very difficult to analyse in spatial ...
344 views

### What is the Effect of Multiplying a Function by the Unit Impulse Function in the Frequency Domain?

I know about the the shifting property of the impulse function in the time domain as can be seen in equation $(1)$. $$\int_{-\infty}^{\infty} f(x)\delta(x - a)dx = f(a)\tag{1}$$ But what is the ...
1k views

### Why do frequencies of analog signals range from $-\infty$ to $\infty$ while frequencies of digital signals are restricted to $[0,2\pi]$?

In Fourier analysis while dealing with discrete-time signals, frequencies range from $0$ to $2\pi$ why? Intuitively how can i understand it?
97 views

### Is it true that each and every signal has multiple frequency components?

Usually when we observe spectrum of a signal,we see multiple frequency components, each having different contribution to amplitude But is it true that each and every signal has multiple frequency ...