Signal Processing Stack Exchange
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Questions tagged [frequency-spectrum]

The frequency spectrum of a time-domain signal is a representation of that signal in the frequency domain.

The frequency spectrum can be generated via a Fourier transform of the signal, and the resulting values are usually presented as amplitude and phase, both plotted versus frequency.1

Any signal that can be represented as an amplitude that varies with time has a corresponding frequency spectrum.

Source: Wikipedia.

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What is meant by "spectral moment"?

I have consulted the almighty oracles of google and wiki, but I cannot seem to find a definition for the phrase "the moment of the spectrum". A legacy work text I am reading uses it in the following manner, defining the number of zero-crossings per…
Spacey
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Could someone please explain to me the relationship between frequency bands and channels?

Specifically, I am a tech writer working with WiFi hardware, and I need to understand why the 2.4GHz frequency band has only three channels, while the 5.0 GHz band has so many more. I would presume that, since they're both "frequency bands", they…
Kyle Pearson
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Spread-spectrum systems and multipath fading

I didn't find a suitable tag for this, but figured it would fit under "Frequency spectrum". Which of the Spread-spectrum systems listed here are most resistant to multipath fading? Please, briefly tell me why? The Wikipedia article above lists these…
G.Vanem
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Calculating a spectral envelope

I'm trying to calculate the envelope of an arbitrary spectrum but I'm slightly lost as to the best way to do this. I've looked at cepstral enveloping but its very fiddly and I can't seem to get it to give the right results. I've also tried LPC but…
Goz
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Expressing 2D Gabor transform as 1D spectrum

The Gabor transform (Short-Time Fourier Transform with Gaussian window) is represented as $U(t,\omega)$, where $t$ is the time, and $\omega$ is the frequency. The author of a monograph (Seismic Inverse Q filtering, pg. 190) is asking for the Gabor…
Nicholas Kinar
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Spectrum Width vs Data Carrying Capacity

Newbie struggling to understand why a larger chunk of signal bandwidth is needed to carry more information. For example, why do you need more bandwidth to carry video as opposed to voice or CW? Apparently missing some fundamental concept here. Have…
georgers
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Difference b/w Spectral Entropy and Flatness Measure

What is the difference between Spectral Entropy and Spectral Flatness? As far as I understand, both the terms can be calculated from the power (or amp) spectrum, and describe the flatness (whiteness) of the spectrum. If you wanted to distinguish the…
Ted
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Periodicity and fundamental frequency detection algorithms

I have some time series datasets which are periodic, and I'd like to pick out the fundamental frequency of the data and take the average over a fundamental period. Questions: 1) Would something simple like taking the FFT of the time series data and…
Kris
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Does whitening with PCA correspond to power spectrum flattening?

I'm finally making some headway in understanding data whitening, but I have a question now relating what I think of as "data-based" whitening to the situation where there are time-varying signals. So in the "data-based" world, suppose I have a…
lmjohns3
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Band limited signal: Infinite time duration, time limited signal : infinite bandwidth

In signal processing, there is a time-frequency duality. Band-limited signals have infinite time duration and time-limited signals have infinite bandwidth. Where can I find a proof of this and is there some intuitive explanation for this? I am not…
Nash Brewer
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why is moving towards higher frequencies so important in frequency spectrum?

As we know, as frequencies becomes higher, bandwidth becomes higher.And, according to channel capacity theorem, channel capacity increases with higher bandwidth. Also, energy is directly proportional to frequency(E=hf). So, if frequency increases,…
user3156370
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what is meant by biased and unbiased Autocovariance sequence estimate?

In nonparametric spectral estimation method what is meant by biased and unbiased Autocovariance sequence estimate and why most commonly biased one is used? I have the answer to the second question from Peter Stoica (SPECTRAL ANALYSIS OF SIGNALS)but…
anil
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Building a spectral envelop of FFT'd audio

I'm trying to figure out how to create a good spectral envelope of a signal. Basically I am, at present, taking a windowed section of audio applying an FFT and generating a bar chart style representation of the magnitude of the spectrum. However…
Goz
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Relation between Power Spectral Density and RMS of the signal

I have a pressure signal at two locations (r=1 and r=1.3). I found the power spectral density (PSD) and the root mean-square (RMS) of the signal. My question is why at r=1 the PSD is higher than the PSD at r=1.3 while the RMS at r=1 is less than RMS…
Math
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Encounter 0 when calculating log power spectrum

To convert power spectrum to a log-scaled one, how to define log10(X(k)) if X(k)=0 for some k? For sake of illustration, I brief my process as follows which is a convention one: Calculate the magnitude spectrum X(k) of the time-domain signal x(n)…
Fred
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