Questions tagged [frequency-domain]

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21 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 ...
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1answer
25 views

Names of system functions in frequency domain

I was just trying to refresh my systems theory known from long ago, and I realized that I had forgetten the name of the basic functions. Specifically, what are the names of these functions ...
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1answer
49 views

Is pitch detection for bass instruments a solved theme?

I would like to know if pitch detection is a solved theme for an instrument like a bass (bass tones). Is it, or there is always a percentage of error rate on the detection?
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1answer
54 views

Why use PSD to analyze a signal instead of its Fourier Transform?

Let's imagine I have a perfectly known signal $s(t)$ and I want to analyze its frequency components. I noticed that mostly everyone would use the PSD of $s(t)$ to do that, instead of simply use the ...
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1answer
45 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 ...
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Which part does the filter in CNN drop to have the same size as input image?

In CNN (Convolutional Neural Networks), we have an image by size $N\times N$ and a filter by size $H\times H$ which usually $H < N$. When we want to find the transform of the image and the filter ...
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20 views

Does it make sense to apply convolution in the frequency dimension of a fourier transformed signal?

What I have is more likely a theoretical question. Since I am not from a signal processing background it is hard for me to grasp the issue in using convolution in the frequency dimension of a Fourier ...
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1answer
23 views

Is it possible to prove that dither VS PWM can result the same output?

Assume that we have a SISO transfer function model $G(s)$ and we want to look how the output looks like when we have a input signal $u(t)$ that looks like this: $$u_1(t) = \left\{\begin{matrix} 50 + ...
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2answers
62 views

Proof of fourier transformation of multiplication of two signals

I've been trying to find a proof of the following, but still I m unable to proof it, can someone help me? $$ ℱ[x(t)g(t)] = \frac{1}{2\pi} [X(\omega)*G(\omega)] $$
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1answer
35 views

Time domain analysis vs frequency domain analysis? Applications wise? [closed]

When do we use time domain analysis and when do we use frequency domain analysis? As far i studied i know that when we need to study individual sinusoidal components of a signal, we choose frequency ...
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3answers
61 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 ...
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1answer
33 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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1answer
58 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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1answer
60 views

Derivation of Circular Mean Square Error

I would like to understand how Eq. (36) in [2] was derived: The rationale behind the definition of circular sample mean in Eq. (37) is clear, but there is no motiviation for the CMSE definition in Eq....
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2answers
32 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. ...
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1answer
32 views

Continuous frequency grid to discrete grid

I am designing a controller for a system using several methods, one of which is a discrete method. In the continuous time I am looking at a logarithmically spaced frequency grid in the range $$\omega \...
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1answer
53 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 ...
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34 views

Convolution Theorem using DCT

I am trying to digest this paper. [2002] Anna Usakova. Using Of Discrete Orthogonal Transforms For Convolution So far, I've been successful with DFT and DHT. Could someone give a hand with DCT? I am ...
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1answer
45 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 ...
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1answer
52 views

Harmonic Product Spectrum from FFT output to the fundamental frequency

I'm trying to do the HPS algorithm on my FFT output, but I'm stuck here. My signal is from a bass (cable), 16bits, 48.000Hz. I split in time domain the array of the whole record into multiple arrays ...
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2answers
96 views

How to avoid overtones in audio signal

I'm trying to make a program that catch and audio signal of a bass and show the notes that have been played. My program: Gets the sound and put it in a double data type array. (48 000Hz, 16bits) ...
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2answers
100 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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1answer
29 views

Time and Frequency Domain Relationship

Why do we say that a good time response means a bad frequency response?
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1answer
155 views

How do I perform a time domain phase shift in the frequency domain?

I've seen some information on this topic around, but I don't quite understand it. I have a time domain signal. I understand that if I want to time shift this signal, I can do so by multiplying its ...
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45 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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27 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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1answer
56 views

Absolute value based AM envelope detection viewed in the frequency domain

In my understanding when a passband AM signal is demodulated with an envelope detector taking the absolute value restores the original baseband version of the signal and the low-pass filter removes ...
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1answer
38 views

GPS Receiver in Frequency Domain

I'm trying to transmit and receiver the GPS payload in both Time and Frequency Domain. For transmitting and receiving in time domain : ...
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1answer
66 views

Spectrogram of an executable binary [closed]

One of the approaches I have been searching so far is the application of utilizing Neural Network to classify Spectrogram images, which is heavily used in speech recognition. I am conducting an ...
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17 views

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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4answers
99 views

Remove brighter regions in an image on frequency domain

I'm newbie and maybe this is not the right place to ask this question, or this question has no sense. I'm very interested in working on filtering images on frequency domain. I have found a few ...
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1answer
150 views

get poles and zeros of frequency response

I am working on a python based LTSPICE project. I would like to get poles and zeros of AC simulation data. Is there a way to get them under use of the magnitude and phase out of the frequency ...
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43 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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2answers
72 views

Idea for Noise Level Estimation / Automatic Thresholding in the Presence of Peaks

I have the fft of some signal, and want a rough estimate of the noise level in order to choose an appropriate threshold for our peak detection algorithm. In general, the fft contains mostly noise with ...
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1answer
63 views

Sampling of frequency response

Let's consider any physical quantity depending on the frequency. For example, the impedance of a certain electrical component: $Z(f)$. Now, imagine to measure it in a continuous interval of ...
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1answer
58 views

Filtering in the Frequency Domain - DIP [closed]

I am trying to do some filtering with a gray scale image in the frequency domain. I am just getting into matlab after some time away from any signal processing or coding and can't quite seem to get my ...
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1answer
256 views

Do negative frequencies count towards null-to-null bandwidth?

I am aware that negative frequencies do not normally count towards the bandwidth when transmitting in the baseband. However when specifically asked to look at the null-to-null or zero-crossing ...
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43 views

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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1answer
87 views

How do I decide which frequencies are signal and which are noise?

I have an arbitrary recorded digial signal, on which I have run a Fourier transform. I'm not sure what conventions are on a case like this, but I have 1024 frequency bins. Second bin is the highest ...
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25 views

How to search for irregular signals: Fourier, DWT or k-means?

See my notebook here I want to search for irregular time signals in a data set of ~3 500 000 time signals. By eyeballing I have found hundreds of flat and oscillating signals, but just a few that are ...
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1answer
51 views

What is Imaginary in Fourier transform?

How to plot graph of $e^{-t}$ in frequency domain. What would be the axis? If its Fourier transform is $1 /(1+j\omega)$, then how can we plot imaginary on frequency domain (amplitude vs frequency ...
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1answer
48 views

Contributions to a DFT frequency bin

So, a frequency bin is centered around an interesting frequency $f_0$. Assume the spectrum is such that there is no spectral leakage from other frequencies to that specific frequency $f_0$. Now. I ...
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2answers
113 views

Is the value of a frequency bin of a DFT-output the average of the 'real' frequency values within that bin's range?

I am wondering whether the value of a frequency bin with a certain resolution is the average of the fourier transform values of the 'real' frequencies within that bin's range.
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1answer
51 views

Yet another fft question - a vocoder

Lets assume a pipeline X: ...
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2answers
94 views

Can a 1-dimensional signal be in a domain other than the time or frequency domain?

In signal processing I have only heard of signals being in the "Time" domain or in the "Frequency" domain, but are there situations where a signal is not in either of these? If so, what are these ...
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1answer
1k views

Extract frequency data from MP3 file

I want to do frequency analysis of audio data, basically trying to figure out what the notes are in a song algorithmically. The standard approach is to decode the MP3 into PCM data and run it through ...
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68 views

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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1answer
49 views

What is the result of fourier transform of an image

I am new to computer vision and Fourier transform concept. I have examined some codes. In those codes, an image is performed Fast Fourier transform by using the function ...
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2answers
363 views

Circular Convolution Matrix of $ {H}^{H} {H} $

We all know that Discrete Fourier Transform (DFT) corresponds to circular (not linear) convolution. That is to say, if $x(n),h(n)$ and $y(n)$ is the original signal, the filter and output signal in ...
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1answer
238 views

Purpose of multiplying fft output by Hann window?

I'm working with some acoustic propagation models at the moment. A feature I've noticed in 2 of these models is that the output of the model is often multiplied by a Hann window in the frequency ...

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