Questions tagged [frequency-domain]

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$\tt ifft()$ function - absolute vs real form

I have multiple files from an experiment in frequency-domain that I would like to use ifft() function to convert to the time domain in R to apply signal processing ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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:...
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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 ...
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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 ...
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849 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, $I$ ...
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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 ...
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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 ...
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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 ...
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mp3 encoding in the frequency domain

Let's start with an arduino signal, which can be periodic over time. When this signal is converted from analog to digital it "turns" into a series of bits. At this point, is this signal in ...
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Plot Power Spectrum of Noisy Image in Python

I've been asked to plot the power spectrum of an image where I added Gaussian noise to it. However, I am very new to Image Processing so I don't know exactly how to approach my problem. I calculated ...
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Frequency filtering in the frequency domain vs. time domain

As a DSP newbie, I've stumbled into doing band pass filtering (of pre-recorded IQ data) in the frequency domain - which allows brick wall filtering (I'm just setting the IQ values of each consecutive ...
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non-causal cascade filtering process in frequency domain

if i have linear filter that operate in frequency domain filter length is L (Overlap and save method) if there is no computational time, i get L input signal and fft and multiply filter and ifft the ...
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Fundamental Frequencies of different instruments

I'm trying to study what differentiates different instruments in terms of frequencies, timbre, etc. By studying a few different samples of notes, I've come to the conclusion that for flutes the ...
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Analytic image using 2-D Hilbert transform

I am working on a problem of phase (/phase derivative) retrieval from closed fringe patterns. The paper https://opg.optica.org/ao/fulltext.cfm?uri=ao-58-16-4420&id=413113 which uses a pseudo-...
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Calculating PLV on frequency-domain?

I need to calculate Phase Locking Value of an EEG signal. My data is in frequency domain, it was transformed with Short-time Fourier transform. The formula for PLV is: I see it is a function of time ...
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PSD of DWT details signal

I am working on a project involves sensor data analysis. I have a data for entire year that is sampled every 15 minutes. I used DWT (db4 up to three levels) to analyze the high-frequency content of ...
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Frequency offset estimation accuracy

To improve frequency offset estimation, we could: Use the second order interpolation / equation in the frequency domain based on the coarse estimation fc, e.g. BPSK frequency offset estimation; Zero ...
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Why is the mel filter bank used to create a mel spectrogram?

The formula for converting frequencies from Hz to mel scale is as follows: $$2595\log(1+f/700).$$ So why is the mel filter bank used? What is the origin of the mel filter bank?
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Frequency domain filtering: must filter coefficients always be conjugate symetric?

While trying to do frequency domain filtering of audio signals using windowed overlap-add methodology, I came across some pre-calculated frequency domain coefficients. I noticed that the coefficients, ...
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219 views

phase offset extraction using matched filter

I'm looking for an application of detecting the drift of a received signal carrier frequency from ADC clock of the receiver (in case of no drift, ADC clock should be optimally an integer multiple of ...
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1 answer
99 views

ouput of low pass filter

$$y[n]=(-1)^n w[n]+w[n]$$ $n$ ranges from $-\infty$ to $\infty$ where $w[n]$ is output of frequency response block with cutoff frequency = $\pi/2$, and input is unit impulse function. I know ...
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347 views

Frequency and Order maps

I'm new to python and I'm using it to analyse accelerations from an accelerometer ie. vibration analysis. For that I need to plot 2 types of diagrams: 1) Frequency map; frequency and time on the axis ...
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103 views

Time Frequency bin

I am doing research in audio signal processing for DOA estimation. I came across the term Time-Frequency bin. I have gone through several articles but none of them specify a TF bin rather it specifies ...
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Where can I find more information about how to create filters on frequency domain?

I'm newbie and I'm very interested in filtering images on frequency domain. I haven't found a lot filters on frequency domain and I wondering how can I create new ones. How can I create new ones? ...
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92 views

Range Migration Algorithm in FMCW MIMO RADAR

I’m using a FMCW MIMO radar [77-79 GHz] with a virtual linear array made of 48 channels. I’m wondering if the adaptation of the range migration algorithm (typically used in SAR processing) is ...
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Find repeating sequences in audio file

I have a long audio file (12+ hours). I know that there are some unknown small (2 minutes each or thereabout, it varies) repeating (not bit by bit: it is recorded with a mic) chunks in it, repeating ...
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Generating a phase modulation frequency spectrum with jitter

I would like to produce a frequency spectrum plot like this: (from All About Circuits) I know that one can take the modulation frequency and multiply it by a given order and scale by the modulation ...
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Is there a criterion that says at what point you can distinguish 2 partially overlapping Lorentzian peaks?

If you have 2 Lorentzian peaks that partially overlap and you have some frequency resolution df (your points in frequency space are separated by df) and both Lorentzian peaks have FWHM $\Gamma$ is ...
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Plot Background Noise

I am a total newbie in signal processing. I have been trying to plot on simulink a time/frequency domain noise in PLC (Powerline Communication) that matches a real-world research "...
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What is the best spline to interpolate freq analiser graph

the question is as it is in the topic: What is the best spline to interpolate freq analiser graph? I am looking something simply and fast to implement. I read about catmull-rom it looks it could be ...
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5k views

Operations applied to functions in time domain and frequency domain

I am trying to make a succinct summary of how algebraic operations in the time domain translate in the frequency domain (via the use of Fourrier/Laplace transforms). Here is what I have derived so far:...
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Frequency Domain Equalization [Sources request]

When I read papers, I often see the term "Frequency Domain Equalizer". I do not understand what a "frequency domain equalizer" is. Do they mean equalizers like MMSE, LMMSE? Or is there an equalizer ...
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Poles and zeros from FRF

How can I determine the poles and zeros of a system given its frequency Response? I can understand how one can find the Frequency response from poles and zeros of a system. Is it possible to do it ...
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292 views

Determining Valid DTFT's

Are the following frequency domain signals valid DTFT's (Discrete Time Fourier Transforms)? Answer yes or no, and justify your answer. a) $X(\omega) = \omega + \pi$ b) $X(\omega) = i + \pi$ c) $X(\...
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FFT frequency domain averaging and zero padding

I'm trying to get the average frequency response of an entire piece of audio by splitting it into segments, doing an FFT on each one, and averaging the magnitudes together. Its working great until I ...
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534 views

FFT of irregular shaped data

I have an irregular shaped 3D image that I want to do frequency domain filtering on. Currently I simply zero-pad the data to make it a cube, then do an fft. I was wondering if this was a valid ...
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1 answer
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') ...
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Going from an MFCC coefficient to Hz range?

I have not worked with MFCCs before, but I am faced with the observation that the 5th MFCC of a signal is actually of interest for me in my speech research. In order to understand why that one is ...
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-1 votes
2 answers
256 views

Smoothing in frequency domain and impulse reponse of the filter in time-domain

I have a low-pass signal in frequency domain, $$\left[f_{min}=0, f_{max}=20\,\mathrm{GHz}\right]_{n=100}$$ After re-configuring the input signal as $$X=\left[-f_{max},\ \dots\ -f_{min},\ \mathrm{DC},...
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LP to BP transformation steps

Considering the following problem, What i know to convert from LP signal to BP signal is to: Draw the FD of the LP equation From it I can draw the FD for BP From this graph I can deduce the equation ...
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-1 votes
1 answer
417 views

Alignment of signals for ensemble averaging? Something else?

I have been applying ensemble averaging (adding signals of different trials to obtain one signal) to improve Signal to noise ratio in my data. I have achieved good results in terms of classification ...
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-1 votes
1 answer
410 views

fft2 of interferometric image - how to interpret the result in term of dominant frequency

I have an interferometric image which shows fringes at a certain frequency, basically a dominantly periodic signal overlaying the information that I want to extracthere are the fringes that I want to ...
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2k views

Effect of frequency shift on a sound signal

I had two sound files and did the following to it: ...
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