Questions tagged [power-spectral-density]
The Power Spectral Density (PSD) is the distribution of signal power over frequencies.
774
questions
-2
votes
1
answer
18
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 ...
- 1,001
0
votes
0
answers
17
views
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 ...
- 1
3
votes
2
answers
73
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 ...
1
vote
0
answers
37
views
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 ...
- 111
1
vote
1
answer
82
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 $$...
- 65
0
votes
0
answers
36
views
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 ...
- 11
6
votes
2
answers
536
views
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 ...
- 61
0
votes
1
answer
73
views
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 ...
- 1
2
votes
0
answers
49
views
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 ...
- 45.9k
0
votes
1
answer
85
views
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) ...
0
votes
0
answers
25
views
Compute a waveform with given autocorrelation function
In the past few days I have been stuck with the problem of recreating the derivation shown in this paper, where they try to construct a waveform with a certain autocorrelation function.
Given a ...
0
votes
1
answer
27
views
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 ...
1
vote
1
answer
90
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 ...
- 13
9
votes
4
answers
965
views
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 ...
- 422
1
vote
1
answer
57
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 ...
- 11
0
votes
0
answers
44
views
Distribution of Power Spectral Density in white noise
I have a signal $s$, of which the PSD I call as $S$.
So,
$$ S(\omega) = \frac{1}{N} \left|\sum_{n = 0}^{N-1} s(n) \exp(-j\omega n)\right|^2 $$
I have a closed form expectation of the above mentioned $...
- 107
0
votes
0
answers
46
views
Periodic peaks in power spectrum
I have a noisy(blue) and clean(red) signal. I have windowed them by a hanging window and used Matlab pspectrum() to plot their power spectrum.
I see a periodic peak at noisy(blue) one which is spaced ...
- 263
0
votes
1
answer
59
views
How to calculate to power of a uniformly distributed noise?
I was wondering how I would calculate the power of a noise, if I have a uniformly distributed white noise between $-\frac{q}{2}$ and $\frac{q}{2}$? My approach was to use the formula
$$\int\limits_{-\...
- 3
2
votes
1
answer
89
views
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 $\frac{f_\text{s}}{N}$. ...
- 21
0
votes
0
answers
9
views
How is received power distributed in partially used channel?
I want to learn how the RSSI is distributed in received signal in an OFDM block. When a UE transmits a signal, assume it allocates certain number of resource blocks (RBs), for instance 10 RBs in 20 ...
- 1
1
vote
1
answer
63
views
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.
...
- 263
0
votes
0
answers
19
views
How to measure synchrony between EEG frequency bands illustrated in PSD values
I am investigating the synchrony measures among EEG frequency bands. However my dataset has only PSD values (in frequency domain). I found out that measures like Granger Causality are good but they ...
- 1
0
votes
0
answers
17
views
Generalized distribution of Power Spectral Density at each Frequency Point
I have an expression for the expectation of the power spectral density and I call it $F(\omega, \Theta)$ where $\omega$ is the frequency and $\Theta$ are the parameters. I have some measurements of ...
- 107
0
votes
1
answer
50
views
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.
<...
- 25
1
vote
1
answer
129
views
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 ...
- 27
2
votes
1
answer
85
views
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 ...
- 107
0
votes
1
answer
100
views
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 ...
- 9
0
votes
1
answer
46
views
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 ...
- 9
0
votes
1
answer
40
views
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 ...
- 9
0
votes
1
answer
84
views
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 ...
- 103
2
votes
0
answers
53
views
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) ...
- 153
1
vote
1
answer
203
views
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 ...
- 11
1
vote
0
answers
33
views
1
vote
0
answers
59
views
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:
...
- 123
5
votes
1
answer
179
views
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 ...
- 266
1
vote
1
answer
45
views
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 ...
- 87
0
votes
1
answer
63
views
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.
- 25
0
votes
1
answer
22
views
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 = -...
0
votes
1
answer
90
views
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 ...
- 43
3
votes
3
answers
116
views
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 ...
3
votes
0
answers
85
views
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 ...
- 31
1
vote
1
answer
309
views
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.
...
- 173
2
votes
1
answer
190
views
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 ...
- 211
2
votes
0
answers
131
views
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 ...
- 21
0
votes
0
answers
90
views
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.
...
- 173
1
vote
1
answer
60
views
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. ...
- 211
0
votes
1
answer
59
views
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 ...
- 33
0
votes
2
answers
411
views
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
6
answers
558
views
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
<...
- 87
5
votes
4
answers
253
views
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, ...
- 45.9k