Questions tagged [frequency-domain]
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343 questions
1 vote
1 answer
71 views
Interpolation error between even and odd FFT
Upsampling a spike [100 0 0 ...] with rfft - irfft gives quite different results for input lengths even or odd. Here's a plot for 100 and 101: Why the difference ? ...
- 638
2 votes
1 answer
79 views
Automatic noise level estimation and occupied bandwidth detection
I am trying to detect occupied bandwidth by looking at the spectrum of the signal in environment. The scenario is mostly blind and the dominant noise is the white Gaussian noise of the environment. ...
- 123
1 vote
1 answer
83 views
Why sampling in frequency domain generates sidebands although those frequencies are not present in signal?
The frequency domain of a signal provides information of all the frequencies that makes up that signal. I am reading about sampling, and I want to understand why sidebands(copies of original spectrum) ...
- 21
4 votes
3 answers
1k views
I am confused with non-causal signal processing methods. Do they make sense?
Most time-frequency domain methods used to analyze how signals behave in systems — such as Fourier or Hilbert transforms — are inherently non-causal. But this approach seems conceptually inconsistent ...
- 41
0 votes
0 answers
33 views
How to interpret the frequency spectrum of function 1-2t
I have coded a discrete fourier transform script in python sageMath. I am trying to analysis the frequency spectrum of the function 1-2t. The graph for 1-2t from 0 to 4 is below: When I run the DFT ...
- 111
0 votes
4 answers
154 views
From the DFS perspective, why does tapering a signal with a window function concentrate energy in a DFT?
For simplicity and concreteness, let's assume you are taking the DFT of a signal which is a pure sinusoid but at a frequency that does not line up with a frequency bin in your DFT. I'm wondering why ...
- 313
0 votes
2 answers
81 views
Time domain signal representation via integral over frequency range
I'm trying to understand the math of the signal passing through the IQ-mixer and then going to ADC. I found some paper preprint, where there is a description of this process. On page 9, the authors ...
- 379
1 vote
2 answers
107 views
How are detection limits calculated in DSP?
I have two profiles acquired from the same device with one parameter changed between acquisitions. They both have a base profile with a comb of period 4 appearing as a "spike" every 4th ...
- 11
0 votes
1 answer
160 views
How the equivalence of two signals multiplication in time domain and corresponding frequency domain convolution actually works for discrete signals?
I'd like to show the equivalence of two signals multiplication in time domain and corresponding convolution of them in frequency domain in Python. Direct ...
- 379
1 vote
1 answer
135 views
The Discrete Fourier Transform (DFT) Pair of Rectangular / Indicator Function
I'm trying to properly understand the fft and tired to recover the sinc function from its Fourier transform, i.e. an indicator ...
- 59
2 votes
4 answers
1k views
For the square wave signal, why does a narrower square wave correspond to more spread in the frequency domain?
Consider the square wave. As we decrease the pulse width $T_1$, it seems that the positive Fourier coefficients (located in the central area/lobe) are spreaded out across more frequencies. In fact, if ...
- 643
0 votes
0 answers
38 views
Synchrosqueezing of frequency-wavenumber spectrum
I am bigenner to signal processing. I am working on improving frequency-wavenumber spetrum obtained from multisensors sound data. I read about Synchrosqueezing as a technique widely used to compensate ...
user67390
1 vote
2 answers
364 views
Linear convolution of a 100 sample time series and a 20 tap filter in the frequency domain
I came across this question on an internship application. For context, I'm three years into my bachelor's for electrical engineering right now. I have learned continuous and discreet convolutions, so ...
- 11
1 vote
1 answer
202 views
transform time series different length and sampling rate with frequency domain
i want to transform my time series (each same scale) to frequency domain. There are 2 things to conside: some time series are longer then the other i have different measuring intervals which means e....
- 11
1 vote
2 answers
231 views
In the frequency domain of a phase-shift keyed signal, why there are are prominent frequency components which are multiples of sampling frequency?
In the frequency domain representation of a digital phase modulated signal, why there are prominent other frequency components which are multiples of the sampling frequency, other than the main ...
