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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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Definitions of Discrete Power Spectrum and Discrete Power Spectral Density

I have been reading lots of posts about the scaling factors in PSD, and related topics on this forum. My understanding of the topic has been greatly improved. Thankyou all. I just need a little more ...
S_holmes's user avatar
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What does the covariance of a power spectral density between frequency points mean [duplicate]

I am struggling to understand the meaning of the covariance of PSD (Power Spectral Density) between two frequency points ($f_1$ and $f_2$). The covariance of a function $s(t)$ in time domain $t$ is a ...
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How to interprete the standard deviation of the psd in dB?

I have done a power spectrum density estimate using Bartlett's method. However, I was wondering if it is also possible to get a sense of the variation of the averaged spectra. I have plotted the mean ...
Helmut's user avatar
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Calculate standard deviation of spectral desity in a Bartlett's method fashion?

I have done a power spectrum density estimate using Bartlett's method. However, I was wondering if it is also possible to get a sense of the variation of the averaged spectra. Unfortunately, I have ...
Helmut's user avatar
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Bartlett's method: Order of normalisation?

I want to estimate the power spectrum of a given signal using Bartlett's method. I understand the general purpose of the method. However, I do not get my head around the algorithmic description of the ...
Helmut's user avatar
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How to calculate a mixer noise?

I am struggling to calculate a mixer output noise, but I am stuck in the understanding how to calculate it formally, could someone please help with reasoning or give a reference? I assume that we use ...
Pierre Polovodov's user avatar
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Lomb-Scargle or Periodogram for non-uniformly sampled data

I have non-uniformly sampled data and I'm trying to look at its Power Spectral Density (PSD). For that, I looked at the Periodogram PSD estimate of an interpolated (with uniform sampling period) ...
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Does power spectral density change with sampling rate?

The power spectrum $\texttt{PS}$ of a (white noise) signal depends on the frequency resolution, $df=f_s/N$, where $f_s$ is the sample rate ($\texttt{Hz}$) and $N$ is the sample size. The power ...
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Convert MUSIC algorithm to EV

I write some code, but result looks very strange: ...
Dmitry  Sokolov's user avatar
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Prony method doesn't work

I have used the code from: https://github.com/quantumlib/OpenFermion/blob/v1.5.1/src/openfermion/linalg/wave_fitting.py#L41-L76 try using with my signal: ...
Dmitry  Sokolov's user avatar
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Units of 6.02*N + 1.76 as an FFT noise floor

I'm working on estimating the FFT noise floor for a data acquisition system my colleagues and I are designing. I've read MT-001 several times. In general, I think I get it. However I'm a little stuck ...
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The baseband sampling frequency when the negative spectrum is considered

Suppose I have a signal $x(t)$ of bandpass bandwidth of $2W$ Hz. The sampling frequency must be at least $2W$ in baseband, because the largest frequency component is $W$ Hz. I understand that, when we ...
Math_Novice's user avatar
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Can a large drop in the PSD indicate the presence of a periodic noise?

I was wondering if a large drop in the plot of the PSD of a sensor measurement could indicate the presence of a periodic noise. Here is my PSD: Thank you.
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EIRP conversion from given value at one polarization to both bolarization when antenna operate at both polarizations

For an antenna that operates in both polarizations, how do I convert its EIRP density, given in dBW/Hz assuming one polarization, to the dBW/Hz value for both polarizations? For instance, if EIRP = -...
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Compute SNR of a signal with not clear fundamental frequency in PSD

I'm trying to compute SNR from a signal in which by visual inspection I can guess the SNR but I cannot compute it because I cannot find the fundamental frequency of the signal as I should be. On the ...
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Why can two different signals have the same periodogram?

I have just started trying to self-study an intro course on signal processing. I have just been introduced to the periodogram and have a hard time understanding why completely different signals can ...
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How to extract human voice from cluttered signal?

I have a signal which has human speech, background voice and noise as it can be seen in below figure. I have calculated its power spectral density (PSD) using many different methods which can be seen ...
sdkmlcngz's user avatar
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Periodogram (Welch) has different levels depending on length of segment/ resolution

I am trying to compute the PSD of a signal in MATLAB using Welch's periodogram method as shown in the code snippet below. ...
Tommy Wolfheart's user avatar
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In what way does the cross-spectral density of two signals describe their similarities?

I’m trying to gain a deeper understanding of what the cross-spectral density of two signals represents. I know how to compute it, and I know it represents a covariance of sorts, as it appears in the ...
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Effect of down-sampling to PSD from auto-correlation?

I have a problem to evaluate the PSD from auto-correlation. As you know, PSD is the Fourier Transform of the auto-correlation. But I observe the spur at PSD when I calculate the auto-correlation with ...
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What happens if you use the Fourier transform of the autocorrelation of a non-WSS process to compute power spectral density?

The Wiener–Khinchin theorem states that the power spectral density of a wide-sense stationary stochastic process can be obtained through the Fourier transform of the autocorrelation of the signal i.e. ...
Tommy Wolfheart's user avatar
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What is the meaning of the scaling difference between my DFT magnitude squared plot and my periodogram plot?

I have an EEG recording of duration $2\text{s}$ with sampling rate $f_s=200 \,\text{Hz}$ and, as a mathematician, wish to familiarize myself with some of the standard terminology in signal processing. ...
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Emperical mode decomposition problem

I am using Empirical Mode Decomposition (EMD) algorithm to decompose a vibration signal generated by outer race bearing defect using case western réserve University data. I am facing a problem: unlike ...
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FFT of signal data with windowing, overlapping and averaging

This is my first ever question here so the help is really appreciated. I am performing FFT on a signal. I want to perform windowing, 50% overlapping and averaging to the signal. There is a function <...
Anique Ahmed Khatri's user avatar
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6 answers
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What's the meaning of negative frequencies after taking the FFT in practice?

Suppose I have a signal $x(t)$ with baseband bandwidth $W$ Hz and power $P$, and consists of $K$ samples, and I draw the two-sided power spectral density (PSD) of this [baseband] signal in MATLAB as <...
Math_Novice's user avatar
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4 answers
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Bandpass Stationary Stochastic Process

I was following this interesting post by a new user Rubem Pacelli and got stuck at Proakis' referenced definition (see Section 4-1-4 starting on page 159 here). The math, all repeated further below, ...
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The normalization of the autocorrelation function and how it changes the definitions you've learned about signal analysis in communication systems

Since this question is book-oriented, I will kindly ask you to accompany it with a book that is considered by many researchers the bible of Digital Communication: Proakis - Digital Communications, one ...
Rubem Pacelli's user avatar
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Power spectral analysis in baseband vs bandpass

I have two signals $x_1(t)$ and $x_2(t)$ both with a baseband bandwidth of $W$ Hz. $x_1(t)$ is transmitted over carrier frequency $f_1$ Hz, and $x_2(t)$ over carrier frequency $f_2=f_1 + \frac{W}{2}$ ...
Math_Novice's user avatar
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averaging power spectrum from multiple signal of different length

I have multiple physiological signals (EMG - muscular electrical activity) that are all of different length (one may even be 2/3 times longer than the smallest one). These signals are from 2 types of ...
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Signal power after frequency shift with different frequency than the carrier frequency

I have this received signal in passband $$ \begin{split} r(t)=&\Re\left\{\tilde{x}_1(t)e^{j2\pi f_1t}+\tilde{x}_2(t)e^{j2\pi f_2t}\right\}\\ =&\Re\left\{e^{j2\pi f_1t}\underbrace{\left[\tilde{...
Math_Novice's user avatar
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Random telegraphic noise and Lorentzian noise power spectral density

Following the example of the Lorentzian noise power spectral density shown above (ref), I would like to clarify the following: In the first figure (labeled by (c)), May I please know why the constant ...
Greta's user avatar
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While calculating the power spectral density (PSD), why is there a roll-off at the end depending on the sampling rate?

In these power spectral density plots shown above (taken from the web 1,[2]), the spectra show a roll-off at the highest frequencies, as shown in the figure. For my own example, when I calculate PSD ...
Greta's user avatar
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How does Power Spectrum remain symmetric in Z domain?

Can you tell me how the $P_x(z)=P_x^*(1/z^*)$ is mathematically correct. I can understand the $P_x(e^{jw})=P_x^*(e^{jw})$ as $P_x$ is real value. But why take the Z domain representation in this way ($...
Kuchi Yashwanth's user avatar
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How to detect signal in spectrum without empirical data

Let's say, I have got a spectrum of a signal with noise using fft: For a human it's pretty obvious that there is a signal with a frequency of about 51Hz. But what is the mathematical apparatus behind ...
Clayn's user avatar
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power of a modulated signal

I have verified that for a pure carrier the power is 0 dBm. But when i see a qpsk/psk modulated signal the power reduces. How can i calculate how much the power has been reduced? Is there any ...
mark's user avatar
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Generating signal in a different frequency band than another signal but transmitted at the same time

I have a signal $x(t)$ of bandwidth $W_1$ transmitted over carrier frequency $f_1$, and another signal $i(t)$ of bandwidth $W_2$ transmitted over carrier frequency $f_2$. The main lobe of both signals'...
Math_Novice's user avatar
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Frequency probabilities from Fourier transform

Fourier transform is an estimator of frequency. Because its an estimator, there is always some uncertainty associated with my coefficients as described by the Fourier/Gabor limit. I'm wondering how to ...
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Confusion about definition of power spectrum

I'm trying to get a good handle on the spectral theory of random signals, but there seem to be two different definitions of the power spectrum whose relation is not clear to me. On the one hand, we ...
Othman El Hammouchi's user avatar
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Can we detect WiFi from Spectrograms using signal processing?

I'm looking for some suggestions on detecting wifi using spectrograms (abs magnitude only) . My project involves a wifi driver which outputs a spectrogram whenever it scans the channel . Can we use ...
Aryan's user avatar
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3 answers
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How do you find the null to null bandwidth for the signal below?

My tutor does not explain it very well. Can someone please explain to me the reasoning and what null to null bandwidth actually is?
MALLU's user avatar
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Why do we normalize the fft power by sampling rate and number of data points to find the PSD?

When finding the power spectrum density (PSD) from the $N$-FFT of time-domain signal $x(t)$ of $N$ data points (assuming $N=2^n$, $n\in\mathbb{Z}^+$), we normalize the power of the FFT by the sampling ...
Math_Novice's user avatar
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Estimate Power spectral density using Discrete wavelet transform form pycwt

I want to estimate the Power spectral density using Discrete wavelet transform and a Morlet Wavelet. Bellow you can find the function I am using. Any comments or suggestions on wether or not the ...
Jokerp's user avatar
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How to plot in MATLAB the PSD of two signals with different bandwidths

I would like to plot the power spectral density (PSD) of this signal $$y(t) = x(t) + i(t)$$ where both $x(t)$ and $i(t)$ are binary phase shift keying (BPSK) signals with baseband bandwidths $W_x/2$ ...
Math_Novice's user avatar
1 vote
2 answers
1k views

Why power = variance = rms^2 in the White Noise process?

I'm an electrical engineering student studying statistics. I saw in an article that White Noise variance = power = rms^2. Could you explain how this expression is ...
Jiwon's user avatar
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Where does the following expression for stationary Gaussian Noise come from: $\langle \tilde{n}(f)\tilde{n}(f')\rangle = \delta(f-f')\frac{1}{2}S_n$?

First, the definitions: Definition (Gaussian process) A random process $X(t)$ is a Gaussian process if for all time points, $t_1,\ldots,t_n$ the random variables $X(t_1 ),\ldots,X(t_n)$ have a ...
DetectorNoise007's user avatar
1 vote
1 answer
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Does the resolution of a timeseries affect the estimate of the power-spectrum when using np.fft.rfft and does it comply with parseval's theorem?

I have been trying to estimate the power spectrum of a timeseries using fourier transform. I have tried to do this using two variations of the spectral density estimate using np.fft.rfft. The two ...
Jokerp's user avatar
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Understand carrier power, output power and dBC?

I have a question regarding the concept of carrier power, output power and power relative to carrier (dBc). Suppose I have a carrier frequency of 4Hz and signal bandwidth = 4 Hz. The signal span is ...
Md. Hasan Rahman's user avatar
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Why does Python welch give me a different answer from MATLAB's pwelch?

I am trying to implement the following line of MATLAB code: [pxx, f] = pwelch(data,[],[],4096,F_S) in Python. Knowing that MATLAB using a Hamming window type that ...
JoJo's user avatar
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SDR - Manual FFT PSD vs pylab PSD

I am trying to calculate the power spectral density step by step using numpy FFT and comparing it to the PSD calculated by pylab PSD. Difference b/w plots of both methods can be visualized from in ...
Abdul wahab's user avatar
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Wiener filter for vector-valued signal

I'm trying to understand the derivation of a Wiener filter for a vector-valued signal, found in the paper "Kalman filtering in non-Gaussian model errors: a new perspective," IEEE Signal ...
Rodney Price's user avatar

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