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57 views

Problem calculating the average power of a vector?

I am calculating the average power of a vector. I would like to compare the final expression with the simulation. However, they are not equal. Please help me to point out which steps are wrong. Thank ...
2
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1answer
106 views

What is the relationship between the PSD of a continuous signal and the PSD of its periodically sampled one?

In Oppenheim's "discrete time signal processing", it says, How is the equation (10.65) derived? PS: you may try to derive it with Fourier transform of the original and the sampled signals. But i ...
2
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0answers
47 views

Noise analysis with periodogram. problem with different resolutions

I don't understand what happened in my simulation. I would like to perform a trade off between 2 ways to estimate power in frequency bands. I want to detect spurious frequencies. First method: I ...
0
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0answers
32 views

Looking for an algorithm that computes weighted average of frequencies intensity from narrow band in spectrograph

I am searching for the algorithm that takes (audio) signal as an input and outputs weighted intensity of the frequencies of some narrow band (axis X) in time (axis Y). Frequency in the middle of that ...
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0answers
41 views

Interpolation methods for radar and acoustic imaging

A) What are the most common methods used to remap data for current generation imaging radars and acoustic sensors? B) What are some of the pitfalls in these methods? For example, in the past, at ...
0
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1answer
44 views

I have run an FFT now want to get the mean value in the 8hz - 13hz range?

I have a matrix [66 x 100,000] (it's some EEG data, across 66 electrodes) and want to find the mean power in the 8-13hz range. How can I do this? I have so far: ...
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2answers
36 views

Signal de-amplified before doing Power Spectral Density. Any effect?

I have a time-series signal (voltage, specifically) that was divided by 1000 before doing an FFT-based Power Spectral Density (PSD) (using LabView), giving the output in dB. Question: What is the ...
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0answers
25 views

What is OSNR in Fiber Optics?

I have seen that the SNR is measured for optical fibers "OSNR". What is the difference? Is there any equivalent?
1
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1answer
51 views

How to detect a spiky signal embedded in a periodic signal

Say I've got a signal that I know is composed of periodic components. However, I'm worried that there are "spiky" events that are embedded in this signal, and potentially occurring periodically. I ...
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0answers
47 views

Spectral estimation from noisy time-series data

This is the first time I'm posting a question on here so I hope I'm doing it right. I've tried searching on here for an answer but haven't found anything particularly relevant. I have some data ...
1
vote
1answer
123 views

1/3 Octave Analysis

Good Morning! I am new in signal processing and I am trying to do a work in noise control of an electronic steering lock device (ESL). My aim is to calculate the loudness (Zwicker Method- ISO 532 B) ...
1
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2answers
64 views

Parseval's theorem - Average Power

I want to calculate averaged power of a time-domain signal by means of its spectrum. I guess Parseval is the right tool. So I sample a sinus of 100 Hz 10000x within one second. Unfortunately the sum ...
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0answers
67 views

Autocorrelation Function and Power Spectrum

My aim is to determine the power spectrum of a signal of finite duration using Its autocorrelation function Performing FFT directly on the time-domain data The function is defined as follows in ...
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0answers
23 views

use multiple Fisher test for periodic components

I know that there is a Fisher test for periodic component detection, one example is there: http://www.mathworks.com/help/signal/ug/significance-testing-for-periodic-component.html But let us suppose ...
0
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0answers
39 views

calculate variance of periodogram

I would like to know how to calculate the variance of periodogram? As I know variance is a big problem of periodogram. Namely increasing length of time series increases also variance of periodogram, ...
3
votes
2answers
133 views

PSD estimate using FFT - scaling and units

I know that similar questions have already been asked – I have read the answers, yet I am still not sure if I understand the topic properly at some points. I want to use FFT to calculate PSD ...
0
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1answer
54 views

Is the quantization noise white here?

If I have the following power spectral density of the quantization error can I tell that quantization noise is approximately white? Can you please provide some justification?
0
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1answer
141 views

Power spectral density interpretation

After reading this question: PSD (Power spectral density) explanation I am still a little confused as to what extra information the PSD gives us over simply taking the magnitude of the fourier ...
0
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0answers
72 views

How do I find the corner (aka cutoff) frequency?

I would like an equation for finding the corner frequency in the attached periodogram. Note the periodogram is plotted in logs. As you can see there is a white noise component over the lower ...
0
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2answers
100 views

What can we deduce about variance when we are given the noise spectral density?

Given the noise spectral density ${N_0\over 2} = a$, what can be deduced about the variance? In the case of a two-symbol canal(/cable), and when $T_0 = 1$. Is it that, $\sigma_X^2 = {N_0 \over 2} ...
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0answers
37 views

What is SNR of signal with additive white gaussian noise [duplicate]

Calculating the power of AWGN should be equal to infinity as PSD is constant and its integration is infinity over all frequencies. Hence for any signal with finite power mixed with AWGN, SNR should ...
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0answers
48 views

Using Spectral Density To Compute The Autocorrelation Function

I have a spectral density function $S_{xx}$ and I want to compute the discrete autocorrelation function $r_{xx}[n]$ from it but I can seem to figure out how.I have $$ S_{xx} = 3e^{-2jw} + ...
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0answers
120 views

Analyzing an undersampled recording from an antenna with matlab?

I'm trying to analyze the power spectral density of a signal recorded from a Ham radio antenna. The signal is about 30 seconds long, recorded at a 48 kHz sample rate. The frequency is center frequency ...
3
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1answer
87 views

What assumptions should be used to invert spectrum into time domain data?

This question comes from a realistic problem that how to obtain a time domain wind pressure from known wind spectrum. Or similarly, gets rail surface curve from spatial rail spectrum. Obviously, ...
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0answers
32 views

Estimating a Power Spectrum from a Time Series [duplicate]

What are the best ways to estimate the power spectrum of a given time series? Any pointers to review articles or book chapters would be appreciated. A little more information: When estimating a ...
0
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1answer
59 views

Get spectral picture from a wavelet transform

According to my previous question, I have changed the generate command to: y=generate1(100,1000,1); and got the following picture: Now I want to test a ...
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1answer
56 views

Spectral structure of sinusoidal model

Let us consider the following code: ...
0
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2answers
953 views

How to Show A OFDM Symbol's PSD in Matlab

I'm trying to suppress the sidelobe of OFDM but having troubles showing its spectrum in Matlab. After IFFT, I get a time-domain signal, but in which way I can get its spectrum(or PSD)? I want to ...
2
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0answers
68 views

How to properly express periodogram over analog frequency?

Assume a signal $x[n]$ with $N$ samples and its $N$-point FFT $X[k]$. Assume also the simplest power spectral density estimator: $$ S_x[k] = \frac{\left| X[k] \right|^2}{N} $$ With this estimator, ...
1
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1answer
263 views

How to generate AWGN with given power spectral density

I am a little unsure about the generation of a additive white Gaussian noise, so I would appreciate to hear from you if I`m doing it correctly. My goal is to generate the time-domain noise ...
3
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2answers
86 views

How do we know that CTFT of the autocorrelation function is the PSD?

I know that the Fourier Transform of the autocorrelation function is the Power Spectral Density. But how can we arrive at such a result intuitively? Is it just a theorem?
5
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1answer
123 views

Do waterfalls generate pink (1/f) or brownian (1/f^2) noise?

Does anybody know if natural waterfalls generate pink noise or brownian noise? I have tried to search about this but the matches are non-scientific and contradictory. For example Livescience.com ...
4
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2answers
107 views

Why is PSD estimated, and not simply computed?

I apologize if this comes as a basic question, but I am struggling to understand why the PSD can only be estimated and not directly computed. For example, this thread discusses several such PSD ...
2
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0answers
35 views

Stationary processes and their power

The top answer to this question: Power spectral density vs Energy spectral density states: However if random process is stationary, then it is for sure that it has some finite power over some ...
2
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1answer
162 views

Recover signal from its power spectral density

I was wondering whether we can recover a signal $x(t)$ from its power spectral density using signal processing techniques.
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1answer
57 views

Is there a general relation between mean power and period

I posted this question at Math Stack Exchange a few weeks ago without any luck. It occurred to me I might have more luck by posting it here. The basic question is whether there exists a known ...
3
votes
1answer
632 views

AutoCorrelation using FFT of power spectrum

I have a chunk of data (samples) that need to do autocorrelation using FFT method. All data are real and lies between -1 and +1. What I have done follows: Zero pad the window with the length equals ...
2
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0answers
501 views

Matlab: Estimating power spectral density of an experimental data?

How do I estimate PSD in matlab ? There are lots of methods to estimate, depending on application. I am using an experimental data to identify faults ( e.g. interturn fault of electric motor), which ...
2
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2answers
123 views

Clarification Needed: Power Spectral Density of Real Signal

For a real signal, the power spectrum will have Hermitian symmetry. If I consider the one-sided spectrum (as negative frequencies, or anything above the Nyquist frequency are redundant) must I then ...
0
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1answer
112 views

Compute PSD from a CSV file

I'm sorry if my question might be simple, but I don't have a strong background on signal processing. I have a csv file of a 8 MHz bandwidth, sampled with a resolution bandwidth of 100 KHz. What I want ...
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0answers
107 views

when trying to nomalize a power plot , do we normalize it after converting it to db scale or before it?

I have two power plots. I am trying to normalize it for comparing them . So , do we normalize it after converting to db scale? or do we normalize the power as such?
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1answer
2k views

Power spectral density vs Energy spectral density

I read the following on Wikipedia: Power spectral density: The above definition of energy spectral density is most suitable for transients, i.e., pulse-like signals, for which the Fourier ...
6
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2answers
3k views

Spectral Entropy Calculation in MATLAB

How do I calculate the Spectral Entropy of a signal in MATLAB ? I know the basic steps but it would be nice if someone can help ? Calculate the power spectrum of the signal using FFT command in ...
1
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2answers
513 views

White noise vs. delta pulse and Ultraviolet catastrofe

Everybody explains that white noise has all frequencies equally strong. But, this immediately means that Ultraviolet catastrofe inevitably happens if power > 0 stays constant at any frequency and, ...
2
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1answer
350 views

Frequency detection

What I have: A digital signal sampled at Fs composed of a QPSK modulation at Fmod plus some additive white gaussian noise. ...
2
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1answer
652 views

Spectrum of a zero-order-hold signal

What does the spectrum of a sampled signal look like if one uses a zero-order-hold? There is some information in: Sampling theorem and Dirac comb, but I am wondering, how to apply this in practice. ...
4
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0answers
162 views

How exactly does MATLAB zeropad?

I am doing some massive number crunching in MATLAB which involves millions of PSD estimations. Each data segment has length 41. So I have been using the multi-taper method with nfft=41 (details below ...
5
votes
1answer
140 views

Cross Power Spectral Density of Unevenly Sampled Data

Here's my problem. The input signals $x$ and $y$ will be having the time value aligned with each other. However, the data are not evenly sampled. I would like to calculate CPSD of both signals. The ...
1
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1answer
303 views

Windowing a time domain OFDM signal

Windowing is a popular method of reducing the spectral sidelobes of OFDM. A popular window usually used for this purpose in the raised cosine (RC) window, because of its tapered and smooth edges. I ...
4
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2answers
6k views

variance of white gaussian noise

it could seem an easy question and without any doubts it is but I'm trying to calculate the variance of white gaussian noise without any result. PSD of AWGN is $\frac{N_0}{2}$ while autocorrelation ...