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1answer
57 views

Plotting Power Spectrum (Matlab)

I want to make a plot of the power spectrum for a .wav sound file, over the frequency range from -2000 to 2000 Hz. Attempt: I used the following code, but the resulting plot is one sided. It doesn't ...
0
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1answer
16 views

Evaluating the spectral density of generated noise through the autocovariance

I'm working on generating noise signals $X(t)$ (with $t \in \left[0,T\right]$ with step size $\delta t$) with a prescribed power spectral density $S_{XX}(f)$ and I'm figuring out how well I am ...
0
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1answer
23 views

Periodogram frequencies not matching with signals

I am new to signal processing world. I am working on a project where we have to find change points using spectral densities. I am running some simulations where in I created a wave which is a linear ...
2
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4answers
71 views

Finding the Amplitude of a Sinusoid in Noise

I'm trying to solve for the amplitude and frequency of a sinusoid embedded in zero-mean gaussian white noise. I am supplied a sample file of a 40000 element array. I first took the autocorrelation ...
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0answers
15 views

Derivation of Doppler Power Spectral Density

I'm looking for an intuitive explanation for the U-shared Doppler PSD and also it's mathematical derivation starting from the definition of auto-correlation function for the doppler scenario.
0
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1answer
23 views

Evaluation of Autocorrelation and Power Spectral Density of white noise through a filter

So say there's a filter with an impulse response of $h(t) = (0.8)^t u(t)$. I'd like to pass white noise through this and figure out the autocorrelation and power spectral density of the output. I'm ...
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0answers
68 views

1/f noise parameter characterization

I would like to characterize 1/f noise in some time series data. I would like to estimate the 1/f noise corner, and the standard deviation of the 1/f noise component and white noise component. The ...
1
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0answers
17 views

Generating 3-dimension $1/f^\alpha$ noise

I'm stumped trying to find a way to generate a 3-dimensional $1/f^\alpha$ noise time series. Basically I want simulate a forcing that is $1/f^\alpha$ in the 2 space dimensions and $1/f^\beta$ in time, ...
1
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1answer
79 views

Calculating energy spectral density function of half-cosine function

I have the following function: $$ g(t) = A\cdot \textrm{rect}\left(\frac{t}{T}\right)\cos\left(\frac{\pi t}{T}\right)$$ How do I find the energy spectral density function? I think? it is defined as ...
1
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0answers
32 views

How do I perform a spectral averaging? Amplitude spectral density

I haven't been doing much signal processing over the years and I'm wondering if my logic is sound. I'd appreciate any input. So, I have a data set with independent variable ($A$) in Frequency ...
1
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0answers
36 views

Quantifying how good I'm producing a spectral density

I recently asked a question here on how to create noise with a specific spectral density $S_{xx}(f)$. The helpful people of this stack exchange told me one way to do it was filtering white noise with ...
1
vote
2answers
74 views

Numerically generating noise time series from spectral density

I'm trying to figure out a way to construct (numerically) time series of random variables given some spectral density $S_{xx}(f)$. I'm interested in various types of spectral densities (flat, ...
3
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3answers
103 views

How to interpret spectrogram correctly?

I have a pressure transducer signal from a reacting mixture available here, which has a sampling frequency of 50kHZ. I have also obtained the spectrogram of the signal with NFFT=256, noverlap=4 as ...
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0answers
17 views

Unit of the area between two power spectra

I calculated the area between two Power Spectral Density curves that are z-score normalized (frequency x normalized Power). What would the units be of the area calculations?
0
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0answers
14 views

Predict the maximum power of a signal in the presence of noise

My question relates to predicting the power of a signal in the presence of noise. The signals I am analysing are discrete quasi-periodic signals (jittered sine waves basically). If I do a spectral ...
1
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0answers
40 views

Why is it better to sample white noise in frequency domain here?

We have a channel $c(t)$ that we want to sample. It can be expressed as $ c(t)= g\ast x(t)$ where $x(t)$ is white complex Gaussian noise and $g(t)$ is a function that we know the PSD of, let's call it ...
0
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0answers
32 views

Error in summation of spectral components

The error associated with a given estimated spectral component $f(w)$ ($w$ is the frequency) of a Gaussian signal follows a Chi-squared distribution with $\nu=2$ degrees of freedom. For instance the ...
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0answers
15 views

Autoregressive Model for EEG frequency analysis?

I want to do EEG frequency analysis in matlab using autoregressive models (e.g. Burg's method). How do I do this correctly? I just treated each channel individually (loop over channels), so I go ...
0
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1answer
100 views

Keeping track of units for spectral energy of discrete signals

The energy of a continuous signal $x(t)$ recorded between $t=0$ and $t=T$ (namely $x(t \notin [0, T]) = 0$) is defined as $$E = \int_0^T |x(t)|^2\, dt.$$ In most signal processing texts I met, the ...
0
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1answer
50 views

How to calculate the discrete power of a discrete signal?

If I have a time series defined by a series like $$ x = [a_1, a_2, a_3, ..., a_n] $$ for time from $t = 1$ to $t = n$ How can I get to the power of the signal in this form: $$ P_x = [p_1, p_2, p_3, ...
1
vote
1answer
61 views

Apply band pass filter (BPF) before calculating the power of a signal (PSD)?

From my understanding PSD tries to give a good estimation on the power each frequency attributes to the overall signal power. If I am only interested in a frequency range $(\omega_0 \leq \omega \leq ...
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0answers
62 views

FFT and Power Spectrum from Time series using MATLAB

I'm trying to better understand some things about FFT so I've asked for a small assignment, in MATLAB, in which I'll make some signal analysis on existing data. All I have is a time series which is a ...
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0answers
48 views

Multiplication of two noise

I have a question on the multiplication of two noise. Suppose I have two noise $n_1[n]$ and $n_2[n]$. I only know their power spectral density $N_1[k]$ and $N_2[k]$. How can I get $N_3[k]$, where ...
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0answers
28 views

Sign of DC Component obtained from FFT differs with the sign of Mean of the signal, Does the sign really matter?

I've been working on 3-axis accelerometer data to predict the gesture of an user. Lot of literature pointed me to consider Frequency domain features for my problem and i'm using Mean of the ...
0
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1answer
90 views

Finding the right measure to compare sound signals in the frequency domain

I am comparing the spectral contents of some sound signals with Matlab. I have quite a few measures but wanted one that represents the centre of gravity of the spectrum. I used SpecCentroid() found ...
0
votes
1answer
96 views

How to find SNR of received DSB:AM signal with white noise after demodulation & LPF'ed?

This is a homework problem so please do not give a full solution. I intend to keep this at discussion-level. Problem Statement I am given the Power Spectral Density (PSD) of a DSB-Amplitude ...
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0answers
17 views

Understanding spectral diagram in Log-Log scale

I have a hard time understanding the signal composition via log-log representation of signal power spectral. For example, in the figure attached On the right is the Spectral Density of signal X and ...
0
votes
1answer
91 views

Power spectrum estimate from FFT

I'm plotting the FFT power-spectrum of a signal in MATLAB. I uploaded the 8000 samples time-series signal in a text file here: http://wikisend.com/download/896484/signal.txt I'm using the following ...
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0answers
20 views

how to apply x and y in cpsd matlab code?

i would like to ask question related to Cross Power Spectral Density function , which in matlab can be estimated using function : cpsd(x,y,[],[],1024,fs) but there is a main question that x and y ...
0
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0answers
17 views

how can I obtain cross power spectral density in MATLAB?

First I apologize because of my weakness of English I want to get cross power spectral density from MATLAB , I had studied MATLAB's help but I dont understand it very well,is there anyone to help me? ...
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0answers
20 views

Power estimation using eigenvalues

There are many different method to estimate power of a signal at a particular frequency or direction of arrival. As an example root music(Matlab rootmusic.m). The question is: do we have a bias when ...
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2answers
84 views

Increase power of signal in Matlab

I have a scenario where I have two OQPSK modulated signals and I need to increase the power of one signal by 3 dBm while keeping the other signal at the same power level. Could someone guide me on how ...
2
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1answer
124 views

How to calculate the energy in the dirac delta function signal?

I'm having DSP for the first time, and after some classes I got confused about the following: Suppose I have a signal which its fourier transform in a frequency band $[ \omega_1,\omega_2] $ is just a ...
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0answers
21 views

Temporal Interpolation of Spectra

The signal of interest to me is the ocean wave height as a function of time at a particular location. Its power or variance spectrum is estimated by buoys at regular time intervals. Specifically, ...
1
vote
1answer
45 views

Voss algorithm and pink noise

the voss' algorithm generated a 1/f series. What does the series mean? For example, we use three dice and the result sequence length is 8. Let's set the sequence is 8,15,6,9,14,10,9,7. Then what does ...
0
votes
1answer
54 views

Obtaining power spectral density without having knowledge about frequency bandwidth or sampling frequency of the signal in Matlab?

Is there a way to plot PSD of a signal which show true frequency amounts ( not normalized one) without having knowledge about frequency bandwidth or sampling frequency of the signal in matlab ?
0
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1answer
180 views

Averaging multiple FFTs in matlab

I have multiple, real, audio signals which I am taking the FFTs. Although they don't come from the same recording, those signals represent the same thing (biologically). I was told that I could ...
0
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0answers
151 views

How do we calculate Power Spectrum Density (PSD) which is given in dB/Hz and not just dB?

I found many definitions for this quantity, PSD. In a document on signal analysis by National Instruments say that it is the amount of power in a unit bandwidth. Let's say P(f) is the power of the ...
1
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1answer
34 views

Has there been any research on time-windowed spectral estimation using more than one window function at the same time?

In the Welch's method, a signal is divided into overlapping segments, multiplied with a window function, and transformed to frequency domain via fourier transform. Why does the method use only one ...
1
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0answers
13 views

What spectral estimation technique to use for finding sharp spectral lines?

At the moment, I am using the Welch's averaged modified periogram method for spectral estimation, which has the frequency resolution $f_s/N$ where $f_s$ is the sampling frequency and $N$ the window ...
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0answers
9 views

Temporal window $\{v(t)\}$ of Welch estimator

The Welch estimate [1] of PSD (power spectral density) is determined as: $$\hat{\phi}_W(\omega)=\frac{1}{S}\sum_{j=1}^S \hat{\phi}_j(\omega)$$ where ...
1
vote
1answer
89 views

Numpy's real fft (rfft) - losing power

Related to another problem I'm having, I was looking into the workings of numpy's rfft2 and ...
0
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0answers
58 views

Analysis with Window before FFT

I have two signals $x$ (see below) and $k$ (obtained by giving circular shift of 106.5849 in $x$). Before I take FFT of both ($x$ and $k$) I want to do window analysis on them. Kindly can some one ...
1
vote
1answer
55 views

How to calculate the noise power for a non-stationary noise?

With stationary noise we have constant mean and variance (let's assume it is Gaussian noise). My first question is, how is the noise power calculated and how it is related to the variance? Now, I ...
0
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0answers
53 views

Lost power while using FFT with apodizing mask

Previously I asked this question about FFT artifacts. The solution that is most easily implemented is using an apodizing mask on the original image, tapering the borders to zero making the image ...
0
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0answers
49 views

What are the applications of Fourier Transform Power Spectrum?

What are the main applications of Fourier Transform Power Spectrum? Can somebody clarify with some examples. Also, what are the advantages of using Fourier Transform Power Spectrum over Fourier ...
1
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1answer
61 views

Power spectrum of downsampled image

I am not sure if this is the right stackexchange community for this question, but here goes. I am generating a Gaussian Random Field (GRF) of a pre-defined power spectrum. In the image below, the ...
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2answers
82 views

Spectral Analysis vs. Spectral Line Analysis

We usually talk about "spectral analysis" but some resources (this paper or this doc) talk about "spectral line analysis". Does this make sense to you, i.e. are the 2 fields actually different or the ...
0
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1answer
67 views

Bartlett's and Welch's Method for PSD

Lets say. I have an image of 100 samples, and I want to find the presence of smaller image of 24 sample using cross-correlation in the fourier domain. I use Bartlett's and Welch's method for PSD, ...
0
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1answer
89 views

Finding Correlation response in fourier domain

Lets say I have a system that is trying to find a small image (assume all images are grayscale) within in an image by using correlation. So this system has the baseline image, and I input 5 different ...