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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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Time-varying shot noise generation

I'd like to model the behavior of photodiodes, the input is like data bits (0 & 1) where each bit is represented maybe with 100 samples / bit and the bit rate is $B$ bits/sec with period $T_{bit}=\...
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How to get the total power of the signal from sound pressure levels?

I have the Sound Pressure Levels (SPL(f)) of noise signals in the frequency domain. I need to get the total acoustic power of the signal between a range of frequencies. Initially, I compute the Power ...
Student's user avatar
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How do you average the power spectra across multiple samples to compare 2 conditions?

I have physiological signals from samples under 2 conditions and want to compare the difference in frequency content between the conditions. Specifically,I'd like to compare the average power spectrum ...
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Generating time-domain noise from PSD

I have a question regarding generating a time-domain noise from the power spectral density (PSD), this was addressed in this question (How to generate time-series from a given one-sided PSD?) but I ...
Mohamed Osama's user avatar
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Noise spectral density and windowing

I am wondering about the definition of Power Spectral Density, in the context of measuring noise, i.e., Johnson-Nyquist (thermal) noise. Usually a windowing method, like Welch's method, is used to ...
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How to do FFT on I and Q DATA in Python

I am Working on a Satellite data, where information is stored in a Raw data exchange format .prd file, i have extracted the information in csv file where i got the I and Q data in decimal, now i ...
Ankit upadhyay's user avatar
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DSSS spectrum not flat

Why is the PSD of the simulated BPSK/DSSS in AWGN not flat? Here are the simulation parameters: BPSK symbols are randomly generated and are {+1,-1} Spreading factor = 128 Spreading code is a randomly ...
BigBrownBear00's user avatar
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Measuring thermal noise of RLC circuit

I am confused about Johnson-Nyquist noise. Specifically, where does bandwidth come in? Thermal noise voltage is usually defined as something like: V^2=4kT∫R(f)df, integrated over a bandwidth. I am ...
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Weiner Filter - why does this computation explain that the necessary filter is a weiner filter?

$X_1(t), X_2(t)$ are random WSS processes with expectation 0, and correlation functions $R_{X_1}(\tau), R_{X_2}(\tau), R_{X_1,X_2}(\tau)$ $n(t)$ is a white noise with SPD $S_n(f) = \frac{N_0}{2}$ ...
Piratemetaldrinkingcrew's user avatar
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Power spectral density convergence for finite samples

Suppose a sequence $\{a_k\}_{k=0}^{\infty}$ has power spectral density $$ S_{\mathbf{a}}(f) := \lim_{n\to \infty}\mathbb{E}\left[\frac{1}{f_0 n}\left| \sum_{k=0}^{n-1} 2\pi f_0 a_k \exp(-2\pi ikf/f_0) ...
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Power spectrum, Power spectrum density and windowing functions

At the moment I have some trouble understanding the different methods. I would like to calculate both the Power Spectrum and the Power Spectrum Density. As the name suggests I thought that $PSD = PS / ...
3dSpatialUser's user avatar
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How can I convert a 1/3rd octave spectrum into a linear spectrum for use as a frequency response?

I have a one-third octave spectrum with 23 frequencies, and I want to use it as a frequency response to filter another spectrum, however that spectrum is specified linear with 2049 points. I know I ...
stix's user avatar
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Average time-domain signal power from correlated Fourier transforms

Suppose I have real-valued continuous-time sequences $x_1(t), x_2(t), x_3(t)$ with Fourier transforms $X_1(\omega), X_2(\omega), X_3(\omega)$. I know that $X_3(\omega)=H(\omega)( aX_1(\omega)+bX_2(\...
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Confusion with Complex Gaussian process with Auto-covariance

I have a complex sequence $z(t)$ in time which I know to be a Gaussian process. I read that the complex Gaussian process is not only characterized by the covariance, but also the pseudo-covariance ...
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Relative loss of power and length of signal

I have EEG signal data from a single channel for 150 similar events (epochs), each spanning 11s which might be accessed from here. I ran the following code block in MATLAB to remove line noise at 60 ...
AvadaMouse's user avatar
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noise synthesis arbitrary PSD

I have noise measurements for a circuit, in units of noise power (measured in Watts against a known load), per frequency bin. For simulation purposes, I wish to synthesize noise with the same spectral ...
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Three dimensional Wiener-Khinchin formula for incompressible isotropic random field

When I am reading Uriel Frisch's book "Turbulence", on page 55 he claimed that the Wiener-Khinchin formula for an incompressible isotropic random field, such as the velocity field of ...
8cold8hot's user avatar
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Lowpass filter to downsample data

I have some data that is sampled at a certain rate (16384Hz). I am only interested in the 10-30Hz region, so I want to downsample the data. My idea to do this goes as follows: I apply some kind of ...
sancholp's user avatar
1 vote
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How does downsampling decrease the noise power?

I read one equation from a technical document, i.e., assuming the time-domain white Gaussian noise samples with variance $\sigma_{TD}^{2}$ in dB are sampled using ADC with sampling rate $f_{s}^{ADC}$, ...
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What Is Continuous White Noise in The Context of Signal Processing and Broadly

How can one define Continuous White Noise in a coherent way? Is there a way to derive it Mathematically? Specifically, is there a way to define it which will works as the model in Signal Processing ...
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Noise variance of DT samples from CT track-and-hold signal

(I will be referring to info from these slides in this post, for your reference.) Consider first for comparison a typical CT low-pass filter, without any sampling, for example implemented by the RC ...
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Abnormal Y-axis value after performing FFT

I have an UFF file which consists of Vibration data. The objective is to convert the timewaveform signal to frequency domain. I have written a python script to convert the timewave form signal to ...
prashanth ramakrishnan's user avatar
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What is the jitter effect on the spectrum of impulse train?

How to derive the sepctrum of $$x(t)=\sum_{n=-\infty}^{\infty}\delta\left(t-nT-\tau_n\right)$$ where $\tau_n\sim N\left(0, \sigma^2\right)$ I assume that the randomness effect should behave as a low ...
Gideon Genadi Kogan's user avatar
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Check whether signal is periodic

I have a signal with multiple frequencies. The frequency changes depending on the amount of air flowing through the fuel snap. The signal resembles a square wave ranging from $0.4$ to $4.5$ Volts and ...
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MUltiple SIgnal Classification (MUSIC) for Frequency Estimation

I am trying to use MUSIC algorithm to detect individual frequencies of an incident signal. I read the original paper and some interesting books that explain the algorithm. I used the following ...
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Selecting Sampling Frequency for Welch Power Spectral Density plot for a daily frequency financial time series data on Python

I have obtained daily close price stock data ( and transformed them to logarithmic returns series data) from a Stock Exchange between 2 financial years, and I wish to generate a power spectral density ...
swagdevotee008's user avatar
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Identifying frequency components only

I have a real world system of a rotating back and forth motion and the time domain data suggests that the data is a random signal (not a deterministic signal). I recorded discrete data points at a ...
LobsterMan123's user avatar
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240 views

MUSIC Algorithm for 2D Power Spectrum

I am trying to use Frequency-wavenumber analysis for estimating speed of sound using two-dimensional data obtained via channel of arrays. The traditional technique is to use FFT to transform the data ...
Engineer's user avatar
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How is the PSD the Fourier Transform of the Autocorrelation function?

I am getting very confused with the textbook I am reading through: Modern Digital and Analogue Communication Systems: 3.8.1 Parseval's Theorem says that: The total power in a power signal is its time ...
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Proof of the Wiener-Khintchine theorem in time domain

In a proof for the Wiener-Khintchine theorem (See p. 572-573) I have seen the following operation being done: \begin{align*} S_{xx}(f) &= \lim_{T \rightarrow \infty} \int_{-2T}^{2T} Rxx(\tau) e^{-...
Finn Heijink's user avatar
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Bispectrum vs cyclic spectrum

One of the definitions of the cyclic spectrum is $$S^\alpha_x\left(f\right)=\lim_{\Delta f \rightarrow 0}\lim_{\Delta t \rightarrow \infty}\frac{1}{\Delta t}\int_{-\Delta t/2}^{\Delta t/2}\Delta f ...
Gideon Genadi Kogan's user avatar
1 vote
1 answer
140 views

Power spectral density plot in terms of non dimensional frequency

I analyzed a voltage signal and plotted the PSD. However, I need to produce a power-spectral-density plot from the data in terms of non-dimensional frequency. How do I calculate the Strouhal number ...
S_saleem's user avatar
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276 views

confusion understanding/interpreting power spectrum of audio in MATLAB?

Please find attached snapshot. I am confused regarding power spectrum in MATLAB as according to google definition in attached snapshot"the distribution of the energy of a waveform among its ...
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How can I plot the power spectra of a ST (Stratosphere Troposphere) Radar in MATLAB to estimate the doppler shift

Respected all, I am trying to plot the power spectra of a ST (Stratosphere Troposphere) Radar to estimate the doppler shift. I am able to obtain a 3D plot between range, FFT point and Power density ...
Shashank's user avatar
3 votes
2 answers
244 views

Power Spectral Density and Energy Spectral Density are both Fourier transform of autocorrelation?

I've been looking into both of these quantities and feel like I have a good understanding intuitively of what they each represent but according to Wikipedia both the PSD and the ESD can be computed as ...
RickarySanchez's user avatar
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Computing Power Spectral Density from FFT vs Welch's method vs Periodogram [duplicate]

I'm looking into different ways to get the Power Spectral Density (PSD) (while toying around with python) of a discrete signal/time series, and I'm struggling to understand why I get (very) different ...
joaocandre's user avatar
1 vote
1 answer
93 views

Power of filtered Bernoulli process

I have some doubt about this exercise. The Bernoulli random process $X(n)$ with means $p=0.5$ is sent in input to a LTI system with impulse response $h(n)= \cos(\frac{\pi n}{3}) R_3(n+1)$ , where $$...
Maghreb_1911's user avatar
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Symmetric Autocorrelation Function vs Asymmetric Autocorrelation Function

I am trying to work through the Cyclostationary Blog to create a cyclic autocorrelation function: I have been given the above equation to determine the cyclic autocorrelation function where tau is ...
SS1's user avatar
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6 votes
2 answers
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Does PSD (dBm/Hz) of white noise depend on sampling rate?

I am confused about signal processing broadband noise like white noise and single-tone noise (sine wave) using FFT. As a starter, I am trying to understand how to normalize white noise properly after ...
anikap's user avatar
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1 answer
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Why are the PSDs off by 100 times

I produced the "elevation vs distance" profile data and their PSD plots, I am trying to get the smartphone estimated profile close to the reference profile. As you can see, the PSD of the ...
qyu38's user avatar
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Optimum Measurement of Sine Wave Amplitude in Noise

There are many related questions posted about estimating sine wave parameters, and this one is closest: Measuring amplitude of a pure sine wave of known frequency close to the noise floor, but none ...
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Spectrum analyzer resolution bandwidth (RBW) for LTE signals

I am trying to measure the maximum output power of an SDR transmitting a 20 MHz LTE signal with a spectrum analyzer. Adjusting the resolution bandwidth (RBW) changes the power spectral density (PSD) ...
Antonio Albanese's user avatar
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Unable to analyze current signals of 3 phase inducion motor

We are receiving 3 phase current readings from Induction motor using CT sensors. I am not aware of what processing is being done on the spot. My job is to do Motor Current Signature Analysis on it ...
Deepak Pawade's user avatar
1 vote
1 answer
372 views

adding subtracting PSD vibration data

We performed some vibration tests on a shaker, with two accelerometers on our setup. One was on the shaker table, to measure the input signal. And the other one was on a flexible part of our test ...
Bertus4's user avatar
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10 votes
4 answers
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When is it true that "the Fourier transform of the autocorrelation is the spectral density"?

I am currently struggling on the book "System Identification: Theory for the User" by Lenart Ljung (freely available here) about the definition of the spectrum (around page 33). As I have ...
NokiYola's user avatar
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1 vote
1 answer
211 views

Delta sigma modulator harmonics appearing with a sine wave input

I am simulating a first order delta sigma modulator (DSM) used as an ADC. The input to my DSM is a full scale sine wave. The power spectral density I expect from the DSM output is as follows : The ...
Nicolate's user avatar
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401 views

How to calculate to power of a uniformly distributed noise?

I was wondering how I would calculate the power of a noise, if I have a uniformly distributed white noise between $-\frac{q}{2}$ and $\frac{q}{2}$? My approach was to use the formula $$\int\limits_{-\...
Ole's user avatar
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2 votes
1 answer
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Correct Windowing Effect at Amplitude Scale

I am trying verify the noise floor returned by Matlab sinad(). I am able to get the results matching by summing power spectrum density with $\frac{f_\text{s}}{N}$. ...
John L's user avatar
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1 vote
1 answer
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frequency present in FFT but not in PSD

I have a simple $0-40 \texttt{Hz}$ IIR bandpass filter. With pure sine inputs I see $60 \,\texttt{Hz}$ is completely gone in the output FFT as expected by looking at the filter frequency response. ...
doubleE's user avatar
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IIR bandpass filter attenuates frequencies within the pass band

I applied Butterworth filters (order=5) that have different cutoff frequencies to a simple signal composed of four sinusoidal oscillations and computed its PSD. <...
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