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Questions tagged [power-spectral-density]

The Power Spectral Density (PSD) is the distribution of signal power over frequencies.

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Why is PSD estimated, and not simply computed?

I apologize if this comes as a basic question, but I am struggling to understand why the PSD can only be estimated and not directly computed. For example, this thread discusses several such PSD ...
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Stationary processes and their power

The top answer to this question: Power spectral density vs Energy spectral density states: However if random process is stationary, then it is for sure that it has some finite power over some ...
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Why the RMS of a PSD curve is the root of the area below

I will try to explain what is my level of understanding of this problem, please correct me if I'm wrong: RMS is the Root Mean Square, it represent the mean value of the input signal. PSD is the ...
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Recover signal from its power spectral density

I was wondering whether we can recover a signal $x(t)$ from its power spectral density using signal processing techniques.
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Is there a general relation between mean power and period

I posted this question at Math Stack Exchange a few weeks ago without any luck. It occurred to me I might have more luck by posting it here. The basic question is whether there exists a known ...
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AutoCorrelation using FFT of power spectrum

I have a chunk of data (samples) that need to do autocorrelation using FFT method. All data are real and lies between -1 and +1. What I have done follows: Zero pad the window with the length equals ...
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Matlab: Estimating power spectral density of an experimental data?

How do I estimate PSD in matlab ? There are lots of methods to estimate, depending on application. I am using an experimental data to identify faults ( e.g. interturn fault of electric motor), which ...
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Clarification Needed: Power Spectral Density of Real Signal

For a real signal, the power spectrum will have Hermitian symmetry. If I consider the one-sided spectrum (as negative frequencies, or anything above the Nyquist frequency are redundant) must I then ...
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Fourier transform of Autocorrelation function, what am I missing here? (Power spectrum)

Given this problem I know that the autcorrelation and power spectrum are fourier pairs, so when taking taking fourier transform of Rxx, one should end up with Sxx However, when I take the transform ...
Jonathan Alvestad's user avatar
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In Search of Voice Activity Detection Algorithms - What happens to the frequency or pitch or speech features as speaker moves away from microphone

Actually i am in search of a Voice Activity Detection Algorithm which could distinguish between voice and non-voice Roughly speaking it must not detect even a bullet sound,even a foot stepping and ...
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Compute PSD from a CSV file

I'm sorry if my question might be simple, but I don't have a strong background on signal processing. I have a csv file of a 8 MHz bandwidth, sampled with a resolution bandwidth of 100 KHz. What I want ...
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Is there any problem with my FFT method?

I am trying to analysis a system by Fourier Transform. my system has 3 dominant modes. (1,0.05) (0.51,0.01),(0.46,0.01) the pairs are defined as (freq,damping_ratio) I've got those result with ...
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What is cross-spectral density- CSD?

I asked a question earlier but I didn't get any answer for it. So now I am simplifying it: what are Cross-Spectral Density (CSD) and Power-Spectral Sensity (PSD)? What is their application? How can I ...
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when trying to nomalize a power plot , do we normalize it after converting it to db scale or before it?

I have two power plots. I am trying to normalize it for comparing them . So , do we normalize it after converting to db scale? or do we normalize the power as such?
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Power spectral density vs Energy spectral density

I read the following on Wikipedia: Power spectral density: The above definition of energy spectral density is most suitable for transients, i.e., pulse-like signals, for which the Fourier ...
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Spectral Entropy Calculation in MATLAB

How do I calculate the Spectral Entropy of a signal in MATLAB ? I know the basic steps but it would be nice if someone can help, Calculate the power spectrum of the signal using FFT command in MATLAB....
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White noise vs. delta pulse and Ultraviolet catastrofe

Everybody explains that white noise has all frequencies equally strong. But, this immediately means that Ultraviolet catastrofe inevitably happens if power > 0 stays constant at any frequency and, ...
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Frequency detection

What I have: A digital signal sampled at Fs composed of a QPSK modulation at Fmod plus some additive white gaussian noise. ...
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Spectrum of a Signal Going Through a Zero Order Hold Sampling System

What does the spectrum of a sampled signal look like if one uses a zero-order-hold? There is some information in: Sampling theorem and Dirac comb, but I am wondering, how to apply this in practice. ...
Ankaios Argo's user avatar
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How Exactly Does MATLAB Zero Pad Signal?

I am doing some massive number crunching in MATLAB which involves millions of PSD estimations. Each data segment has length 41. So I have been using the multi-taper method with ...
Fixed Point's user avatar
6 votes
1 answer
445 views

Cross Power Spectral Density of Unevenly Sampled Data

Here's my problem. The input signals $x$ and $y$ will be having the time value aligned with each other. However, the data are not evenly sampled. I would like to calculate CPSD of both signals. The ...
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Windowing a time domain OFDM signal

Windowing is a popular method of reducing the spectral sidelobes of OFDM. A popular window usually used for this purpose in the raised cosine (RC) window, because of its tapered and smooth edges. I ...
user4259's user avatar
31 votes
3 answers
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Variance of White Gaussian Noise

It could seem an easy question and without any doubts it is but I'm trying to calculate the variance of white Gaussian noise without any result. The power spectral density (PSD) of additive white ...
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RF mask (power spectrum measurement bandwidth)

I'm reading an IEEE standard and it says that the first channel needs to be 50dB below the highest power in a 6 MHz operating channel in 100 KHz bandwidth. It was mentioned several times that the ...
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fit theoretical spectrum to simulated one

I have a bunch of simulated time series, for which I can compute the power spectrum. Generally, the simulated power spectrum can be sketched as follows: I now aim to calculate the features of the ...
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Random signal power spectrum

I have a signal $X(t)=\sum_{n=-\infty}^{\infty} Z_n \delta(t-n\tau)$, $Z_n$ is a random variable with equal possibility of $\pm 1$ and I know the power spectrum of this signal is $\frac {1}{\tau}$ ...
Samuel's user avatar
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PSD (Power spectral density) explanation

I'm trying to understand how the PSD is calculated. I've looked in a few of my Communication Engineering textbooks but to no avail. I've also looked online. Wikipedia seems to have the best ...
user968243's user avatar
2 votes
1 answer
173 views

Guitar String Replucks

I'm analyzing guitar string plucks and sustains. I'm having good success with auto correlation using FFT's. Now I'd like to detect plucks while the string is still vibrating. Since I already am ...
Chuck Carlson's user avatar
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2k views

Getting sound pressure level (SPL) for a frequency band from Welch's derived PSD

I'm using Welch's method (pwelch, in octave) to get the PSD of a recorded sound signal (i.e. pressure level vs. time). I then took the PSD data and took the sum of the amplitude in each octave band (1/...
user3836's user avatar
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Working backwards from PSD to possible signal

I have been trying to reconstruct a random signal from its PSD and am running into trouble. I know that many different signals in the time or spatial domains can result in the same PSD-- I am ...
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Recover High Frequency Loss in a Simulated Power Spectrum

I'd like to ask a theoretical question about power spectra. In MATLAB, by means of a particular approach, I'm trying to generate a Gaussian variable which embodies a particular power spectrum. The ...
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What does double hat mean in Spectral theory?

I was confused about the double hat notation $\hat{\hat .}$ and my teacher and I thought it probably means an estimate of an estimate most of the time, but we could not be 100% sure of its meaning. ...
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Producing Colored Noise from a given PSD Data

I need to estimate (extract/produce) the colored noise of a given PSD Data. I have the following procedure to get the desired results. First of all I calculate the filter coefficiencts using firls ...
technik_duck's user avatar
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0 answers
856 views

difference (or relationship ?) between power spectral density, power density function and periodogram

What exactly is the difference or relationship between power spectral density and power density function? I thought they referred to the same thing but one article I need says to calculate both of ...
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2 answers
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PSD of a windowed signal

Suppose PSD of a signal $x(n)$ is $ PSD_{xx}(\omega)=1$. Now if a window function $w(n)$ of length $ 0\le n \le N-1$ is applied to $x(n)$, what will the new PSD be?
heavenhitman's user avatar
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3 answers
2k views

When negative frequencies cannot exist in practice, why do we calculate power in negative frequency?

Suppose a signal with two-sided power spectral density $N/2$ is passed through an ideal LPF having cutoff frequncy $B\,\mathrm{Hz}$. The output power is equal to $N/2 \times 2B = NB$ Watts. Why not $...
pradeep's user avatar
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27 votes
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What is the difference between PSD and squared magnitude of frequency spectrum?

The power spectrum of a signal can be calculated by taking the magnitude squared of its Fourier transform. Being an audio person, the signal of interest for me would be a time series. How does this ...
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7 votes
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Variance of periodogram estimate of the power spectrum

I have been reading chapter 13.4. ("Power Spectrum Estimation Using the FFT") of the Numerical Recipies Book. Some things related to the expectation value of the "periodogram estimate of the power ...
Tobias's user avatar
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1 answer
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I have a noisy ECG Signal. want to use PSD to analyse the Signal to noise ratio

I have a really noisy ECG Signal which contain, motion artifacts,muscle noise, a very high amplitude noise. I am beginner to DSP. Can someone tell me in a simple language,how do i interpret the ...
Nazura Abdul Halim's user avatar
9 votes
1 answer
12k views

Is autospectrum the same as power spectrum density?

In my slides about signal processing, there is one that mentions the same thing as the beginning of this and this answer, namely that the Fourier transform of a signal, squared is the power spectrum ...
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Difference between power spectral density, spectral power and power ratios

What 'exactly' is power spectral density for discrete signal? I was always under the assumption that taking the Fourier transform of the signal, and then the ratio of desired frequency range ...
anasimtiaz's user avatar
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69 votes
2 answers
36k views

Why so many methods of computing PSD?

Welch's method has been my go-to algorithm for computing power spectral density (PSD) of evenly-sampled timeseries. I noticed that there are many other methods for computing PSD. For example, in ...
nibot's user avatar
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20 votes
4 answers
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How do you calculate spectral flatness from an FFT?

Ok, the spectral flatness (also called Wiener entropy) is defined as the ratio of the geometric mean of a spectrum to its arithmetic mean. Wikipedia and other references say the power spectrum. Isn'...
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4 votes
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Magnitude of Power Spectral Density with Different Sampling Frequency

For exponential signals (sine or cosine), if the sampling frequency $f_s$ is equal to the length of signal, $N$, the magnitude of psd for each sine signal is proportional to amplitude in time domain, ...
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