Questions tagged [frequency-domain]

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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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Why does the frequency in the DFT have to be an integer?

I don't know why the result of DFT and FFT in MATLAB like below images.. fs=128; t=0:1/fs:1-1/fs; x=cos(2*pi*3.5*t); X=fft(x); N=length(x); n=0:N-1; f=fs*n/N; plot(f,abs(X)/N); If I set the ...
5k views

Does the number of samples matter for FFT, and how to get a specific frequency visible?

If I have a signal that has 740 samples, the sampling frequency is 1000 Hz, and I take an FFT of length 1024, are the frequencies I get now 0, fs/1024, 2*fs/1000, ..., 511*fs/1024? I mean, do I get ...
67 views

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 "...
343 views

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How should this fft output be intepreted?

I am currently reading some code, so I can understand how this FFT output is actually been stored. I have a function which computes FFT of audio file, and stores is in the format. ...
295 views

Time-Frequency Analysis of Big Data - Data Size Reduction: averaging the most appropriate method?

Explanation: I would like to analyse the data from an experiment, which investigates the performance of a mechanical component using sensors, that has generated 2000 CSV files. Each file contains 513 ...
122 views

$\tt ifft()$ 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 ...
66 views

Fourier transform of $ne^{-an}u[n]$

I need to find the Fourier transform of the following signal: $$ne^{-an}u[n]$$ The answers start by using the rule of the basic signal: $$a^nu[n] \rightarrow \frac{1}{1-ae^{-j\omega}}$$ and then ...
302 views

Understanding the $\mathcal Z$-transform

I was studying $\mathcal Z$-transforms and found pretty good material on the topic, though I feel I do not have a proper understanding of the concept. Could someone help me clarify this? I know that ...
33 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-...
28 views

Unexpected result after calculating the response of a system in frequency domain

I'm implementing a Python script that calculates the response of a system given an input. The system is $y(t) = x(t-2)$, i.e. it delays the signal by $2$, and the signal is $x(t) = \sin(3t)u(t)$. As ...
1k views

Comparing PSD two signals of different length

I have two time signals A and B which are of different length, length(A) < length(B). Now I calculated the cumulative PSD of both signals. What is the best way to compare this result? If I am ...
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Finding maxima and minima of a continuous time signal by using frequency method?

I have a PPG signal and I wanted to write a code that gives the maxima and minima value of signal by using frequency domain method. Any suggestions?
227 views

What is the type of noise in this image?

what reason could make the noise/effect in this image? Below is the original Thanks!
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Frequency Domain Filtering

Can you create a zero phase IIR filter by transforming its impulse response into frequency domain and only taking the magnitude of that frequency repsone? I have seen this in an open source project ...
Relationship between $y(t)$ and $Y(f)$ in LTI system
If I'm given an LTI system. And I'm supposed to find the input $x(t)$, given $y(t)$ and $h(t)$. Am I able to use this relationship: $$X(F) = \frac{Y(f)}{H(f)}$$ Another question I have is if I'm ...