Signal Processing Stack Exchange
Signal Processing Stack Exchange

Questions tagged [fourier]

327 questions
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5 answers

Fourier Transform minimum sample requirement

Assuming a signal is sampled adequately, what is the minimum size of an FFT window that would allow detecting a specific frequency? Is it necessary to have samples for at least one complete period at that frequency?
hari
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Is the frequency spectrum dependant on frequency, or on imaginary angular frequency?

The frequency spectrum of a time domain signal x(t) can either be written as X(f) or $X(j\omega)$. But how is the later correct? I mean, the frequency spectrum is clearly dependant on the frequency, not on a $j\omega$ part, is it?
user25356
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1 answer

Why does DTFT start and end at the same magnitude?

I would like to know why the spectrum of FIR filters (and maybe all DTFT spectra) start and end at the same magnitude. I guess there is something related to $H(e^{j\omega})$. Thanks
Ali
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List of Fourier coefficientes to simulate musical instruments

I'm trying to find a list of Fourier Coefficients (frequencies/amplitudes, ie, spectral data) to simulate different musical instruments using additive synthesis. Are these data published somewhere? This is for a Math class: I just would like to add…
user15804
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pulsating current in the PWM amplifier vs. the RMS current of the fundamental sine wave after the filter

I want to know how calculate pulsating current on FET switches in a PWM class D amplifier versus RMS current of the fundamental sine wave after the filter. It depends on the positive and negative voltage? Does it depend on the frequency of the…
German Correa
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1 answer

Trying to find the Fourier Series Representation of a sum of Sinusoids

Given a signal: $$x(t) = -5\cos{(93.6\sqrt{2}\pi t - 2\pi/3)} + 3 \cos{(135.2\sqrt{2}\pi t + \pi/13)}$$ I am confused about the right process to take or if there is an easier way than following all the integration. I know I need the fundamental…
user64544
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Fourier decomposition in Matlab

I am doing a Fourier decomposition of sea level series ( to find out one particular contribution within the sea level height). it should be applied subsequently on shifted (by one hour) windows of 96 hours length. I have already the $a$, $b$ as the…
user40707
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help in understanding cosine filter

I was referring to this link https://cdn.selinc.com/assets/Literature/Publications/Technical%20Papers/6059_HowMicroprocessor_Web.pdf?v=20180606-230156 . I am not very clear about the derivation of the cosine filter and how and where it comes from?
gari
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increase the # of points in a DFT, increase the processing

I have a question which is closely related to this one: FFT Processing Gain ^that discussion is a bit general so I want to ask a very objective question to see if I can apply that knowledge: If I collect one million time samples and perform a one…
user8769
0
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1 answer

Phase information

I am quite new to MATLAB and I am currently trying to do some Fourier synthesis. In order to do the Fourier synthesis I need the phase information of the harmonics as a fraction of the period of the fundamental frequency. I am a bit lost on how to…
BranH
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Discrete Fourier Transform bandwidth?

In a problem I'm working on, I have a signal that is sampled 256 times for 3.5 microseconds. After performing a Discrete Fourier Transform on the data, what is the frequency step between the calculated values of Cn? The prompt states that this is…
Parthiv P
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Why don't we use partial Hz?

Hertz seems to be considered a fundamental and atomic unit that we modulate or analyze. 112Hz, 113Hz, etc. Wouldn't we have more to work with if we considered sub-Hertz granularity, e.g. 112.5Hz, 112.59Hz? Why isn't this done (on a wide…
Ken - Enough about Monica
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