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1. Top results related to power spectral density

   • Power Spectral Density from Accelerometer data

     Top Answer

     Answered Sep 29, 2017 · 1 votes

     It depends on what you are interested in. If you want the power spectral density of the acceleration time-series, then s must be the acceleration time-series itself and not the position time-series. Note however that the estimate of the PSD based on that simple algorithm you wrote (called "periodogram") may be insufficient in many cases, to get a realistic estimate of the real PSD. The topic is huge, and literature extensive. You can start from Wikipedia or, if you want a suggestion on a good (but rather tough) book, Percival and Walden. To provide more detailed info, one would need to know much more in detail what you have to do from a physical point of view.

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   • Power Spectral Density - Derivation, Characteristics, Properties, Problems

     In terms of electronics, Power is defined as the total amount of energy that is getting transferred or converted per unit measurement of time, or in general terms Power is defined as the strength or the intensity level of the signal. Power is generally measured in watts (W).

     In this article, we will be going through Power Spectral Density, First we will start our Article with the Definition of Power Spectral Density with an Example, Then we will go through its derivation Properties and Characteristics, At last, we will conclude our Article with Solved Examples, Applications, and Some FAQs.

     Table of Content

     • Definition
     • Derivation
     • Characteristics
     • Properties
     • Solved Problems
     • Applications

     What is Power Spectral Density (PSD)?Power Spectral Density also known as PSD is a fundamental concept used in signal processing to measure how the average power or the strength of the signal is distributed across different frequency components. The Average Power referred to here is known as the mean amount of the energy transferred or distributed throughout a given time range.

     Mathematically, Power Spectral Density (PSD) sometimes also known as Power Density (PD) denoted here as [Tex]S(\omega)[/Tex] for a signal [Tex]x(t)[/Tex] can be expressed as...

     • Symmetric Property
     • Relation Between PSD and Autocorrelation Function
     • Relation Between Input and Output PSD of LTI System
     • Relation Between Power and Power Spectral Density (PSD)

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   • Calculating the Power spectral density

     Top Answer

     Answered Jul 14, 2014 · 4 votes

     You combine the wrong output values to power spectrum lines. There are windowsSize / 2 + 1 real values at the beginning of result and windowsSize / 2 - 1 imaginary values at the end in reverse order. This is because the imaginary components of the first (0Hz) and last (Nyquist frequency) spectral lines are 0.

     int spectrum_lines = windowsSize / 2 + 1;power_spectrum = (double *)malloc( sizeof(double) * spectrum_lines );power_spectrum[0] = result[0] * result[0];for ( i = 1 ; i < windowsSize / 2 ; i++ ) power_spectrum[i] = result[i]*result[i] + result[windowsSize-i]*result[windowsSize-i];power_spectrum[i] = result[i] * result[i];

     And there is a minor mistake: You should apply the window function only to the input signal and not to the zero-padding part.

     ADD-ON:

     Your test program generates 5001 samples of a sinusoid signal and then you read and analyse the first 512 samples of this signal. The result of this is that you analyse only a fraction of a period. Due to the hard cut-off of the signal it contains a wide spectrum of energy with almost unpredictable energy levels, because you not even use PI but only 3.41 which is not precise enough to do any predictable calculation.

     You need to guarantee that an integer number of periods is exactly fitting into your analysis window of 512 samples. Therefore, you should change this in your test signal creation program to have exactly numberOfPeriods periods in your test signal (e.g. numberOfPeriods=1 means that one period of the sinoid has a period of exactly 512 samples, 2 => 256, 3 => 512/3, 4 => 128, ...). This way, you are able to generate energy at a specific spectral line. Keep in mind that windowSize must have the same value in both programs because different sizes make this effort useless.

     #define PI 3.141592653589793 // This has to be absolutely exact!-int windowSize = 512; // Total number of created samples in the test signalint numberOfPeriods = 64; // Total number of sinoid periods in the test signalfor ( n = 0 ; n < windowSize ; ++n ) { value = sin( (2 * PI * numberOfPeriods * n) / windowSize ); fwrite( &value, sizeof(double), 1, outputFile );}

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   • Calculating standard deviation from power spectral density

     Top Answer

     Answered Oct 19, 2016 · 2 votes

     Take the inverse fourier transform, and look at the element at time zero. Note that this is actually just the sum of all the values (\int{X(w)e^{iwt}}dw | t=0 = \int X(w) dw), with some scaling constant applied which depends on how you defined the psd in a discrete frequency domain

     The power spectral density, S_xx(w), is equal to F{R_xx(tau)}, the fourier transform of the autocorrelation, R_xx(tau) = E[x(t)x(t+tau)].

     Since you want the standard deviation, you can get R_xx(0) = E[x(t)^2], and then std^2 = E[x(t)^2] - E[x(t)]^2.

     Unfortunately, it seems you have no way to recover E[x(t)]. Perhaps you already know this is 0?

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2. en.wikipedia.org › wiki › Spectral_densitySpectral density - Wikipedia

   en.wikipedia.org › wiki › Spectral_density

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   The power spectral density (PSD) of the signal describes the power present in the signal as a function of frequency, per unit frequency. Power spectral density is commonly expressed in watts per hertz (W/Hz). When a signal is defined in terms only of a voltage, for instance, there is no unique power associated with the stated amplitude.

3. www.geeksforgeeks.org › power-spectral-densityPower Spectral Density - Derivation, Characteristics ...

   www.geeksforgeeks.org › power-spectral-density

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   Feb 28, 2024 · What is Power Spectral Density (PSD)? Power Spectral Density also known as PSD is a fundamental concept used in signal processing to measure how the average power or the strength of the signal is distributed across different frequency components.

4. community.sw.siemens.com › s › articleWhat is a Power Spectral Density (PSD)? - Siemens

   community.sw.siemens.com › s › article

   • Cached

   A Power Spectral Density (PSD) is the measure of signal's power content versus frequency. A PSD is typically used to characterize broadband random signals. The amplitude of the PSD is normalized by the spectral resolution employed to digitize the signal.

5. vru.vibrationresearch.com › lesson › what-is-the-psdWhat is the Power Spectral Density (PSD)? - Random Vibration

   vru.vibrationresearch.com › lesson › what-is-the-psd

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   Mar 29, 2018 · In vibration testing, the power spectral density (PSD) is a powerful analytical tool for understanding and characterizing random vibration. It estimates the distribution of a signal’s strength across a frequency spectrum.

6. www.rp-photonics.com › power_spectral_densityPower Spectral Density - RP Photonics

   www.rp-photonics.com › power_spectral_density

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   A power spectral density is the optical power or noise power per unit frequency or wavelength interval. It can be measured with optical spectrum analyzers, for example.

7. www.mathworks.com › videos › understanding-powerUnderstanding Power Spectral Density and the Power Spectrum

   www.mathworks.com › videos › understanding-power

   • Cached

   Feb 12, 2024 · Learn how to scale an FFT in a way that provides an understanding of the amplitude, power, and power density spectrum for a time-domain signal.

8. www.sciencedirect.com › power-spectral-densityPower Spectral Density - an overview | ScienceDirect Topics

   www.sciencedirect.com › power-spectral-density

   The power spectral density (PSD) or power spectrum provides a way of representing the distribution of signal frequency components which is easier to interpret visually than the complex DFT.

9. Videos

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     10:19

     youtube.com

     What is Power Spectral Density (PSD)?

     Jan 23, 2023

     58.9K Views

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     20:44

     youtube.com

     Understanding Power Spectral Density and the Power Spectrum

     Feb 28, 2024

     24.9K Views

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     11:53

     youtube.com

     How to Calculate a Power Spectral Density with Python

     Jun 29, 2022

     11.6K Views

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