Questions tagged [frequency-domain]

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What is the frequency representation of nonuniform sampling?

Uniform sampling can be thought of as multiplication of a function $x(t)$ with a Dirac comb function: $$\text{III}_T(t) = \sum_{k=-\infty}^{\infty}\delta(t-kT)$$ Multiplication of $x(t)$ with $\text{...
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Multiplication in frequency domain for a signal containing a whole frequency spectrum

Imagine we have two signals in the frequncy domain X(f) and H(f), for one of the signal H(f) I have the complex pair and the frequncy at which that complex pair exists. The second could be any random ...
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Does LPF limit the maximum sampling frequency of the input signal? [closed]

Consider the system where the signal passes through analog LPF with cutoff frequency of 50 Hz, so the maximum sampling frequency of the input signal could be 100 Hz (according to the theorem). But can ...
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Phase extraction from Fourier transform

Is it possible in principle to correctly extract the phase from Fourier transform? I just tried to do so using Python, here some attempts: ...
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2 answers
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Bandwidth visualization in frequency domain

Consider some signal in frequency domain: the maximum length of which corresponds to the half of the original signal ($N/2$), here $N=32$. It is known that the bandwidth of each sample is $2/N$, so ...
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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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154 views

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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2 votes
1 answer
160 views

FFT and spatial frequency basic knowledge

Using the following website: on how the Fourier transform works (Interested in the Basic Principle part). I found out that if you have 3 pixels closer in the spatial domain you'll get more spaced ...
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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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2 answers
36 views

Power spectral density and auto correlation function: Frequency vs time representation

I have a time correlated periodic signal $a(t)$ with $t=0,1,...,T$ and $a(t+T) = a(t)$ that has been sampled at rate $\Delta t$ and I analyse the signal using the PSD via FFT and the ACF. As far as I ...
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5 votes
1 answer
67 views

Sinc Based Multi Dimension Signal Resampling on the Fourier Spectrum (DFT)

As a generalization of the following questions: The Proper Way to Do Sinc Downsampling (DFT Downsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples. The Proper Way to Do ...
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4 votes
1 answer
69 views

Applying 2D Sinc Interpolation for Downsampling in the Fourier Domain (DFT / FFT)

Related to The Proper Way to Do Sinc Downsampling (DFT Downsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples, how can one apply Sinc downsampling in the DFT / FFT domain ...
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4 votes
1 answer
97 views

Applying 2D Sinc Interpolation for Upsampling in the Fourier Domain (DFT / FFT)

Related to The Proper Way to Do Sinc Upsampling (DFT Upsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples, how can one apply Sinc upsampling in the DFT / FFT domain for a ...
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-1 votes
1 answer
56 views

Real time signal processing in frequency domain

i'm doing realtime signal processing simulation. it could be simple question. if i multiply input L sample fft and M block filter in frequency domain and i do ifft the output come out when index is L+...
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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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2 votes
1 answer
131 views

overlap save method zero padding fft gibb's phenomenon

i'm doing overlap save method in frequency domain. i make hankel function to digital filter using frequency sampling method(to make arbitrary magnitude phase filter). and i do ifft and zero padding ...
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63 views

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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1 answer
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What is The Fourier Transform Formula for 1/(j*pi*t) Types?

I have old homework and solution of that but i didn't understand actually solution. Because i didn't see continous-time fourier transform formula for that. $g(t)$=$\frac{1}{j\pi*t}$ and it asks ...
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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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0 answers
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Arbitrary shape frequency response filter [duplicate]

i want to make arbitrary shape digital filter from equation. that have own magnitude and phase response. the equation is bessel function. the frequency response is below zero phase and real value and ...
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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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2 votes
1 answer
34 views

cascade and summation process in frequency domain using overlap and save method

hello i'm doing signal processing like this S : FFT of input signal from microphone Exp : just gain 1/(Q*J) : include frequency component, I convert this equation to frequency domain digital filter ...
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2 votes
2 answers
103 views

2D Spatial Fourier Tranform on a pressure field

I'm doing some research on Fourier Near-field Acoustic Holography (NAH). The basic theory behind Fouerir NAH is that you take a sound pressure field measurement in a 2d plane p(x,y), 2d spatial ...
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1 vote
2 answers
173 views

Frequency response of an ideal low pass filter

I have an ideal low pass filter having unity gain and cutoff frequency 100Hz. If I provide an input having single frequency component at 100Hz(E.g.- cos(200pi t), will the low pass filter block the ...
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0 votes
2 answers
285 views

Relation of zero-padding and frequency resolution

Consider simple rectangular pulse and FFT of it in Python: ...
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  • 63
0 votes
1 answer
86 views

Frequencies calculation of discrete signal in frequency domain

I have some misunderstanding in definition of frequency resolution of the signal. Here it is assumed that the resolution is: $$\hat{f_k}=f_{signal}\cdot T_{sampling}$$ (which is just relation of ...
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5 votes
1 answer
121 views

The Proper Way to Do Sinc Upsampling (DFT Upsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples

Given a signal $ \left\{ x [ 0 ], x [ 1 ], ..., x [ N - 1 ] \right\} $ what would be the correct way to upsample it in the frequency domain (Sinc interpolation)? Note: Added as a request by the answer ...
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1 answer
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Removing Attenuator and Real Mixer influence on the received Baseband signal in Radar IQ Transmitter - De-embedding

Radar IQ Transmitter Measurement Setup: Waveform Generator + IQ Transmitter + Attenuator + Real Downconversion mixer + Oscilloscope + Post-processing (Hilbert Transform) With the above arrangement ...
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  • 3
1 vote
1 answer
129 views

When if an FFT more efficient than Goertzel?

Given a block, $x[n]$, of M samples. Calculating abs(fft(x)).^2 returns the power spectrum of that block through the use of a $M$-point FFT. I can calculate the same using Goertzel's algorithm. At ...
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0 answers
33 views

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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1 answer
39 views

How to convert passband and stopband frequencies to poles and zeros

I have a NI 9229 digitizer with the following datasheet. The datasheet mentions: a passband frequency of $0.453f_s$ with a flatness of $\le0.1\,\text{dB}$ a stopband frequency of $0.547f_s$ with ...
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0 answers
59 views

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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6 votes
2 answers
223 views

Explain the Process of Spectral Pooling and Spectral Activation in the Context of CNN in Frequency Domain

I am reading the paper Design of an energy efficient accelerator for training of convolutional neural networks using frequency Domain Computation: which uses Frequency Pooling, from Spectral ...
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-1 votes
1 answer
38 views

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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0 votes
2 answers
53 views

unsymmetric fft in matlab

This is the FFT of a 4khz sin signal. I wonder why the negative part and positive part of X axis is not symmetrical? ...
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5 votes
2 answers
241 views

Constructing frequency domain filter from a 2d spatial kernel

Given a 2d spatial kernel $h$, I want to construct the corresponding frequency filter $H$. In theory, $H$ is simply obtained by calculating the DFT of $h$ using a FFT algorithm. But in practice, there ...
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0 votes
1 answer
59 views

Spectrum in real life with Spectrum in theory

as you know it is possible to measure the power spectral density ($|X(f)|^2$) of a certain voltage signal $x(t)$ through a Spectrum Analyzer. As far as I'm concerned, the simplest spectrum analyzer ...
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1 vote
1 answer
337 views

Why is modern control theory in the time domain instead of the S-domain?

I am not sure if I am missing something, but from what I read I understand that modern control systems work in the time domain rather than the frequency frequency or S-domain. Wikipedia article ...
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0 votes
2 answers
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Power Spectral Density as a single number confusion

I'm trying to recreate the results of a machine learning applied to the DSP classification in the article: link. I have a signal (activity measurements from a smartwatch) per patient, so about 30 ...
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  • 111
0 votes
1 answer
121 views

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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0 votes
1 answer
212 views

What does frequency weighting an acceleration signal mean? And How do I frequency weight the raw acceleration data collected?

Disclaimer: I have very little knowledge in signal processing. I'm trying to calculate a Whole Body Vibration(WBV) measure called Vibration Dose value(VDV). $$VDV = \left(\int_{0}^{T}a(t)^4\,dt\right)^...
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1 vote
1 answer
94 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.
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4 votes
1 answer
155 views

Frequency-domain deconvolution: "Direct" filtering vs "Wiener" filtering

Can someone help with clarifying the difference between two approaches to frequency domain "deconvolution: For the frequency domain problem: We want to find a filter $F(\omega)$ which will ...
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1 vote
1 answer
171 views

Measuring frequency response with white noise signal

I need to measure a frequency response of an eleсtric circuit (simple like an RC-filter). I suppose that I can generate an input signal that has spectrum like white noise (for example, m-sequence ...
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  • 9
0 votes
1 answer
117 views

How to do sliding window multiplication in frequency domain

I want to perform the following computations with the impulse response of length L of a LTI system: Multiply the impulse response with a window w(n) of length M << L. Take the FFT of the result ...
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8 votes
4 answers
485 views

Estimation of Amplitude, Frequency and Phase of Linear Combination of Harmonic Signal Beyond the Leakage Resolution of DFT

How can I find a rough ( as accurate as possible) Amplitude of each frequency when there is spectral leakage. Currently, I am dealing with a system that contains special leakage which seems ...
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0 votes
7 answers
347 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 (...
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1 vote
1 answer
209 views

Estimating the SNR of 2-FSK

I have some iq data recordings of a 2-FSK waveform that I've created periodograms from. How do you estimate the SNR of this waveform in the frequency domain? I've heard two opinions: One: Integrate ...
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0 votes
1 answer
43 views

Amplitude in frequency domain of the same signal measured at different bandwidth (f_max - f_min) and different FFT lines

Fourier series in complex form Fourier series in trigonometry form Here, I'm measuring the same signal (an impulse force - or at least as close as possible to an impulse, represented by a knocking ...
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0 votes
1 answer
50 views

Meaning of the frequencies vector using fft

I'm so confused, and it would be nice if someone could clear my head, or at least direct me to suitable references. Assume that I have two gaussian pulses with the same bandwidth in time, but for 2 ...
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