# 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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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: ...
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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: ...
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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 ...
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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 ...
1 vote
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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. ...
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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. ...
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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 <...
1 vote
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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 <...
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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 ...
1 vote
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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 $f_2=f_1 + \frac{W}{2}$ ...
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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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### 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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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