Questions tagged [power-spectral-density]
The Power Spectral Density (PSD) is the distribution of signal power over frequencies.
657
questions
0
votes
1answer
14 views
How to select parameters suitable parameters for a spectrogram
I have a limited background in DSP but I need to generate a spectrogram of an electrocardiography (ECG). I am using the scipy.signal.spectrogram and I need to set ...
0
votes
0answers
45 views
Given a power spectral density of a signal. How to find mean of the signal?
Given a stationary process signal with PSD
$$
S_u = \Lambda(f)
$$
How to find the mean, power, and variance of the signal?
I know how to find power given PSD (integrating from -inf to inf over f). ...
1
vote
2answers
300 views
Conversion of dBm/Hz into watt
I have a noise power density of -174dBm/Hz and a bandwidth of 180kHz. How to convert the resultant noise into watt. I am confused.
First, multiply (-174dBm/Hz) by 180000, then convert the result into ...
0
votes
1answer
74 views
about PSD scailing factor
I also did't understand why they propose a scaling factor of simply 1/N to the FFT, while the matlab function for PSD using periodogram method scales the FFT by 2/(Fs*N)?
Scaling psd is not ...
0
votes
0answers
18 views
Welch PSD Calculation with energy bands
I am working on a Stress Prediction project using the SRAD Dataset. The dataset contains measured signals such as ECG, EMG, Galvanic Skin Response, Heart Rate, and Respiration.
Before any personal ...
1
vote
1answer
52 views
Measure Frequency-Response of Sensor using a Signalsource and Reference-Sensor
Cheers, I want to measure the frequency response of an acceleration sensor.
I have:
A signal source (device similar to a loudspeaker that shakes the acceleration sensor), of which I do NOT know the ...
1
vote
3answers
75 views
How plausible is undetectable (covert) radio communication?
Ever since I found out that coding gain allows you to receive a signal that is well below the noise floor I have been fascinated with the idea of covert radio signals (low probability of detection). ...
0
votes
0answers
31 views
Is this an appropriate way to calculate power and relative power for individual spectral bands (EEG, MATLAB)?
I apologize in advance if this is a dumb question, I'm really new to this kind of analysis. Essentially I have my EEG signal (EEG1) and I'd like to calculate the power and the relative power in each ...
1
vote
1answer
34 views
Obtain PSD data from a noisy signal
I have a noisy source (like a wheel rotating constantly) and I would be measuring signals when the wheel is running. I looked into how I could convert this signal into a PSD and came across Welch ...
1
vote
1answer
92 views
Find some signal x[n] whose auto-correlation function is R[k] [closed]
I want to write a MATLAB code for generating a random message signal 𝑥[n] where its autocorrelation function
is:
R[k] = sinc^2 [1/4 k] where k is an integer. (Hint: Generate a process where ...
0
votes
0answers
39 views
Sample rate vs noise floor in power spectral density measurement
I am trying to measure the noise floor of my picoscope. I want to generate a PSD in volts per root hz that I can compare with specs from other equipment, e.g. a preamp. I gathered some data from my ...
0
votes
2answers
56 views
How does the PSD depend on sample size?
My question is this:
Do the 'amplitudes' of a PSD depend on the number of samples on which it is based?
One definition of the PSD I have found is:
$$
P_{xx}(\Omega_m) = \frac{X(\Omega_m)\cdot\bar{X}(\...
1
vote
1answer
25 views
Does BM3D really need the noise power spectrum beforehand?
I'm at the moment trying to implement a neural network which uses BM3D as a preprocessing step. The problem is, when using the python implementation of BM3D from the paper Collaborative Filtering of ...
0
votes
1answer
41 views
Python - identify mechanical systems from input / output in the time domain
I have a set of input / output time series measurements for different times and machines.
I assume each machine behavior doesn't change over time
output is generally linked to the integral of input
...
1
vote
2answers
37 views
Power spectral density after a modulator block
For random signals, the concept of Power Spectral Density is useful to analyze the signal. It can be shown that if the input $X(t)$ applied to an LTI system of impulse response $h(t)$ has the PSD $S_{...
0
votes
1answer
31 views
Identifying a signal by its power spectrum
Background: There is a method in optics for determining the electric field of light (both intensity and phase) via a three step process:
Add a known phase shift to the light (called the "...
0
votes
0answers
34 views
Get Hilbert marginal spectrum with emd package in python
I want to get the Marginal Hilbert Spectrum in Python using the emd package.
You can estimate the Marginal Hilbert Spectrum as
where,
and A(ω,t) is the time-dependent amplitude modulation and ω ...
0
votes
0answers
27 views
PSD of DWT details signal
I am working on a project involves sensor data analysis. I have a data for entire year that is sampled every 15 minutes. I used DWT (db4 up to three levels) to analyze the high-frequency content of ...
3
votes
1answer
121 views
Generating violet noise with a specific PSD coefficient
I am trying to generate a time-domain violet noise signal with the following power spectral density (PSD):
$$ S_n(f) = A^2f^2 $$
Unfortunately, I am having trouble finding the right amplitude ...
3
votes
1answer
79 views
Is it possible to compute the PSD of s(t)^2 given the PSD of s(t)?
Given a well-behaved signal $s(t)$ given by,
$s(t) = \sum_{i}^{N} \cos( \omega_it + \phi_i) $
with a large $N$ and a well-known power spectral density (PSD), $\tilde{S_1}(\omega)$. Is it possible to ...
4
votes
1answer
79 views
Kay Statistical Signal Processing Estimation Theory Example 7.14
Example 7.14 from Kay Estimation Theory
A common WSS random process has the ACF
$$r_{xx}[k]=
\begin{cases}
1+b[1]^{2}+b[2]^{2} & \text{k = 0}\\
b[1] +b[1]b[2] & \text{k=1}\\
...
0
votes
2answers
150 views
Units of a Fourier Transform (FFT) and Spectrogram [closed]
I am very interested in analyzing signals in the frequency domain.
Units of a Fourier Transform (FFT) when doing Spectral Analysis of a Signal
1.In the previous question, answer the unit for the ...
0
votes
1answer
30 views
Noise Power Spectrum from Log Video Amplifier
I know that if I use a square law detector on band limited noise - let's assume it's rectangular - the noise power spectrum becomes the convolution of the input power spectrum. After lowpass-...
2
votes
2answers
65 views
Computable Time-Frequency Distribution without Cross-Terms
Context:
I have a single receiver that is receiving multiple signals. Each signal has a few strong harmonics, but I don't know the fundamental frequency. I would like to display them on a spectrogram ...
2
votes
1answer
49 views
Having trouble working understanding a noise shaping filter
As context, I'm trying to understand and implement this Von Karman turbulence model in a simulation I'm working on. In order to generate turbulence velocities on the fly using the model, a ...
0
votes
1answer
24 views
Infinity values in statistical analysis of minute frequency data
I'm trying to extract statistical features from power spectral density values in Python. My data is actigraphy data with sampling rate 1/60 Hz (once per minute). This is a sample from my data, "...
0
votes
1answer
43 views
Is "Introduction to Statistical Signal Processing" by RM Gray good for starting?
I am working on noise processes in electronic devices for my studies, by now Ive been doing a fairly large amount of processing of time measurements, like calculate PSD, estimate thermal, flicker ...
0
votes
1answer
59 views
Extracting "frequency domain features" from signal for classification
I have a real signal with only nonnegative values (actigraph measurements). Many papers say they use "frequency domain features" for classification, such as mean, variance etc. But I'm ...
0
votes
1answer
151 views
Generate a time series from power spectral density
I have a model function for a power spectral density (PSD). I want to simulate a time series with a power PSD equal to my model function. After some browsing about how to do this, I came up with the ...
2
votes
0answers
123 views
How to compute the theoretical power spectrum of a first order autoregression (AR1) model
I'm trying to figure out how to compute the theoretical power spectrum of a first-order autoregression model (AR1).
The AR1 model is given as
$x_i = r_1 x_{i-1} + e_i$
where:
$x_i$ is real-valued ...
0
votes
0answers
46 views
How to Normalize a Power Spectral density?
I have a spectroscopy data representing Periodogram of 1024 pts (Periodogram estimate a theoretical PSD), however it is not normalized. How do we normalize the PSD ? The normalization I am looking ...
2
votes
1answer
94 views
Does pwelch function, in matlab, adopt already the correction factor due to the window?
Does pwelch function, in matlab, adopt already the correction factor due to the window?
When we use a window, like hamming or hanning, a correction factor for the amplitude or energy is needed. In ...
0
votes
1answer
57 views
dB octave band spectrum
When I was at the University I did some courses about Acoustic. I always seen the dB octave band spectra, as the Fourier Transform of the dB in time. Now looking at some reference in Matlab, I noticed ...
0
votes
1answer
30 views
Results do not match between manually computed PSD values and those from MATLAB pwelch function
The power spectral density (PSD) of the given input signal $x[n]$ is computed as follows:
...
0
votes
0answers
73 views
Average Power Spectral Density (1D and 2D) of multiple images of different sizes in python
I am trying to calculate avg 1D and 2D PSD of multiple image with different sizes. Any idea how can I do this? Current I'm calculating 1D psd using this function.
The problem here is that each image ...
2
votes
3answers
68 views
What does the intensity values on wavelet transform mean? Amplitude or power?
So when applying wavelet transform, we get a 2d plot. Each point in that 2d plot has a color, showing intensity of something. But I cannot understand if it is an amplitude or power?
0
votes
2answers
38 views
Frequency response terminology: $N(i\omega)$, $Q(i\omega)$
I am reading through an analysis of a system
$$
Y(t) = \frac{d}{dt}X(t) + X(t)
$$
and the frequency response $H(i\omega)$ is defined as
$$
H(i\omega) = \frac{N(i\omega)}{Q(i\omega)} = \frac{1+i\omega}{...
0
votes
1answer
48 views
Extracting EEG Bands from raw EEG signal to match with the Bands calculated on the sensor level
I have recently got my hands on a commercially available single channel EEG Sensor from Neurosky. This sensor acquire raw EEG signal at 512Hz from the frontal part of the human head and also process ...
0
votes
0answers
49 views
A scaling difference between MATLAB's pwelch and Python's SciPy welch
I'm having trouble in python with the scipy.signal method called welch (https://docs.scipy.org/doc/scipy/reference/generated/scipy.signal.welch.html), which ...
0
votes
1answer
45 views
Calculating power of brain signals
I have a dataset that contains EEG (or MEG) recordings of brain signals during some cognitive tasks.
Each row, shows the source estimates of neurons in a particular region.
source estimate contains ...
1
vote
2answers
48 views
Given a noise power spectral density, how long does it take for the underlying process to deviate by a given amount?
Assume we are given a noise power spectral density $S(f)$ for a stochastic process $x(t)$.
What can be said about how long it takes for the underlying stochastic process to deviate by a given amount $...
0
votes
1answer
63 views
What is the meaning of magnitude of the noise power spectral density?
Say we have a noise power spectral density that has the following form (I think the question is the same for more general forms as well)
$$
S(f) = Af^\alpha,
$$
In experiments people usually discuss ...
0
votes
1answer
70 views
Low Pass Filtering, Welch's Method, ENBW
I am working on using Welch's method (https://www.osti.gov/servlets/purl/5688766/) to estimate a Power Spectral Density (PSD). This algorithm involves scaling a set of averaged FFTs by the equivalent ...
1
vote
1answer
82 views
Estimating the SNR of respiration signal
I'm trying to evaluate the SNR of a respiration signal on Matlab environment, so the bandwidth considered is [0.04-1Hz].
The problem is that noise is overlapped on the signal, so I can't evaluate the ...
0
votes
1answer
76 views
Why Bluetooth 2 use pi/4-DQPSK instead of OQPSK?
From the peak to average power ratio point of view OQPSK is better than pi/4-DQPSK. What is the advantage of pi/4-DQPSK compare to OQPSK? Why Bluetooth 2 use pi/4-DQPSK instead of OQPSK?
0
votes
1answer
227 views
Converting from PSD (V^2/Hz) to dBV (1 Volt RMS reference)
I'm having difficulty figuring out how to convert from PSD (V^2/Hz) to dBV (1 Volt RMS reference). The goal is to have a 1 Volt RMS input show as 0 dBV.
Essentially I calculated the PSD of a signal ...
0
votes
1answer
44 views
Spectrum in real life with Spectrum in theory
as you know it is possible to measure the power spectral density ($|X(f)|^2$) of a certain voltage signal $x(t)$ through a Spectrum Analyzer.
As far as I'm concerned, the simplest spectrum analyzer ...
0
votes
0answers
73 views
Why are some Shannon's limit plots exponential rather than logarithmic?
This diagram again. This is clearly not the shape of $\log_2(1+SNR)$ but I very frequently see this instead of this:
But this is also a stupid diagram because it doesn't cross at the origin.
Also why ...
0
votes
1answer
46 views
Why do we need to 'estimate' the PSD
I've read about the PSD of one OFDM symbol for instance being an estimate of the PSD, but how can it be an 'estimate', when it literally is the PSD of that OFDM symbol.
What is actually being ...
1
vote
0answers
23 views
Estimating Average HR from PPG sensor
I am reading Smartphone based Blood Pressure Monitoring via the Oscillometric Finger Pressing Method, which is trying to estimate blood pressure from a PPG sensor and a small applied force finger ...
