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Discussion Groups > Autocorrelation

Comp.dsp is a worldwide Usenet news group that is used to discuss various aspects of digital signal processing.

We found 520 threads matching "autocorrelation"

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The most relevant threads are listed first

Basics of Spectral Density and Autocorrelation Function

lebann - 2005-07-27 21:48:00
Hi, I am trying to grasp the basics of autocorrelation and PSD. I dont have a strong background on DSP, so any help will be appreciated. Here are my questions: (1) why is the PSD, which is given by : PSD(f)=4*Integral[cos(2*pi*f*t)*Autocorrelation from -inf, +inf] is VALID ONLY for freq...Basics of Spectral Density and Autocorrelation Function

autocorrelation matrix

matque - 2007-03-13 12:33:00
I'm trying to copmute the autocorrelation matrix of array outputs and suspect i may be doing something wrong. I'm confident that i'm getting the right result for vectors but when my signal is a matrix it all goes wrong. Looking at the examples below can anyone say if they are correct? e.g. If ...autocorrelation matrix

autocorrelation function C code for full signal

Qiaoke_lily - 2007-12-13 08:12:00
Hi: im interested in finding autocorrelation function for a whole signal instead of a frame only of a signal. i have been refered to a post in year06 (Autocorrelation function, Java or C code) regarding the autocorrelation for a frame of a signal, and i tried to modify the C code for finding the ...autocorrelation function C code for full signal

construction of a signal given its autocorrelation sequence

manolis - 2008-02-25 10:38:00
Hello! My question relates to DSP theory: suppose that i have an autocorrelation sequence in a closed form formula. This autocorrelation sequence may correspond to many different signals. My question is how can i construct a signal whose autocorrelation is the given one? Anyone expert? of a signal given its autocorrelation sequence

Periodic and aperiodic autocorrelation

Treviasty - 2010-06-14 07:36:00
Hello ! I'm starting experiments with compressed pulse radar and I have to choose the best signal to transmit - low autocorrelation sidelobes, good ambiguity function etc. . But there is one thing I can't understand - why there are so many publications and researches about sequences with good per...Periodic and aperiodic autocorrelation

Autocorrelation Tutorial/notes

jpchibole - 2009-03-09 06:44:00
Hey guys I am studying DSP on my own and would like anyone out there who has good notes on Autocorrelation from the very basic to post them for me to use. Second I hope from your notes, I will be able to understand variance and be able to maybe construct an autocorrelation matrix of order 4 and fin...Autocorrelation Tutorial/notes

About autocorrelation matrix of a Periodic correlation function

ryujin_ssdt - 2007-11-01 06:01:00
What properties an autocorrelation matrix would have if the corresponding autocorrelation function is periodic in time with certain integer period T?? I am interested in obtaining something like a cyclic autocorrelation matrix of a cyclostationary process but have no idea where to start from. ...About autocorrelation matrix of a Periodic correlation function

Random numbers with exacty zero autocorrelation

jeroen_trip - 2006-09-04 09:43:00
Hi all, I'm trying to simulate a small sample, say 15 numbers, of white noise. But due to chance, the autocorrelation is not exactly 0. Of course the standard deviation is also not exacty 1 but I can fix that. Is there transformation to get rid of the unwanted autocorrelation?? Many thanks, ...Random numbers with exacty zero autocorrelation

autocorrelation of a downsampled signal

Thierry - 2009-07-12 20:25:00
Hi Guys, forgive me but it has been 10 years since i took a course in signal processing. i am doing some simulations and i need the expression of the autocorrelation (Rx') of a signal after downsampling using the autocorrelation (Rx) of the unsampled signal. I think it should be :Rx'(n)=(1/M)...autocorrelation of a downsampled signal


OZ - 2005-07-18 08:35:00
Hi, I am using an autocorrelation function to calculate the period of a signal. It is a signal which is periodic. My problem is that there are some parts with big amplitudes and some part with small amplitudes. The disadvantage of the autocorrelation is that the big amplitudes are dominant a...Autocorrelation

autocorrelation with 0 lag for LPC in speex library

Anton - 2006-07-28 18:35:00
Hi, I saw in the sources for the speex library ( that they add some value to the first autocorrelation result. The results are used to produce a IIR with a levinson durbin recursion. float d; int i; while (lag--) { for (i = lag, d = 0; i < n...autocorrelation with 0 lag for LPC in speex library

nonstationary autocorrelation but stationary PSD

fisico32 - 2010-05-17 18:18:00
Hello Forum the nonstationary autocorrelation function R(t1, t2) depends on two variables t1,t2. If t2-t1=tau, then R(t1, t1+tau) It turns out that the power spectral density S(w), for a nonstationary autocorrelation function is equal to: S(w)= FT { }, the Fourier transform of the "long-ti...nonstationary autocorrelation but stationary PSD

Autocorrelation function, Java or C code

Thomas Magma - 2006-06-16 14:09:00
Does anyone have any optimized Java or C code for an autocorrelation function. It is my first time needing to do autocorrelation and it seems straight forward enough to be able to write the code myself, but due to the amount of iterations it would be wise to ask for code that already has it's ...Autocorrelation function, Java or C code


John McDermick - 2011-01-03 18:40:00
Is there a signal x for which the autocorrelation sequence r would be a 'flat' line ? For example r = [0.5 0.5 0.5 0.5 0.5 0.5] My guess is no. Can somebody confirm? ...autocorrelation

order of autocorrelation/ASDF and interpolation?

2004-01-16 15:40:00
I asked this before under another subject line, but perhaps it got lost. Assume I want the autocorrelation peak or best least squares fit of sampled data for non-integer sample offsets (e.g. the periods of the frequencies of interest are not a multiple of the sample interval). Should I inter...order of autocorrelation/ASDF and interpolation?

problem with fft on autocorrelation data

acc - 2007-03-31 07:17:00
Hi all, Thanks for reading and please feel free to comment. I am having problems with matlab fft on autocorrelation data. When performing a fft on my normalised autocorrelation data i got a imagnary part that is not equal to zero around x=0 and also at the near end of the x-axis, but, in be...problem with fft on autocorrelation data

autocorrelogram have bias?

rune2earth - 2008-03-24 09:53:00
Hello I'm working on analyzing neuroscience data using the autocorrelation function. I discovered that it has a negative bias (for all lags except zero lag), that exactly matches up so that the sum of all is zero. This is in disagreement with what most textbooks write, for example this taken fro...autocorrelogram have bias?

autocorrelation negative values

Thomas Magma - 2006-08-09 17:45:00
Hi, If your data consists of ones and negative ones then you get negative values in your autocorrelation function, but if your data is ones and zeros you don't. In an autocorrelation plot you often see large negative values on either side of your correlation peak. Is this a good thing or ba...autocorrelation negative values

When does sampled autocorrelation = autocorrelation of sampled sequence?

Oli Charlesworth - 2009-02-28 20:21:00
Hello, It feels like this will be a standard DSP result that I should be able to dig up, but I'm not sure where to look, so here goes! If we have a continuous-time function, h(t) (assuming real and "sufficiently well-behaved" for now), then define the autocorrelation as: r(t) = int { h(...When does sampled autocorrelation = autocorrelation of sampled sequence?

Autocorrelation versus Cross-correlation

Tao - 2007-03-14 06:29:00
Hello, I am trying to determine the frequency of a signal. Samples of the signal are taken from 2 channels at a time. After some filtering, I perform the autocorrelation of each channel, and the cross-correlation of the 2 channels. The autocorrelations, as expected, yield almost identical res...Autocorrelation versus Cross-correlation

Pitch calculation (FFT or autocorrelation)

gjunge - 2006-06-05 07:02:00
Hi, I want to show a Pitch graph/curve of a wave file. I saw that good results can be made by using AutoCorrelation. I have the autocorrelation function and I also have the FFT function, but I don't know what I should put into the autocorrelation function in order to get a pitch line. I have a...Pitch calculation (FFT or autocorrelation)

autocorrelation of linear or logrithimic sweep

2006-01-24 22:11:00
Hi, All, I have been reading quite a number of articles on measuring room impulse response using frequency sweeps, but none of them quoted the analytical formula of the autocorrelation of linear or logrithimic sweep. I remember seeing it in a underwater acoustics book but could not find it an...autocorrelation of linear or logrithimic sweep

image correlation and autocorrelation

fisico30 - 2009-02-17 09:55:00
Hello forum, this is a simple one: I found two forms of autocorrelation for 1D signals: biased and unbiased. Does anyone know the difference? Also, all the signals or images we work with are finite in length. If autocorrelation is carried out, we need to shift the image around with respe...image correlation and autocorrelation

Power Spectrum from Autocorrelation vs. FFT

Navraj - 2007-07-24 16:34:00
I have two questions: 1) Is there a difference b/w the terms 'power spectrum' and 'power spectral density'? They both seem to indicate power vs. frequency. 2) Suppose you are given a random sampled data sequence x[n], and you have to find its power spectrum. - Can we find the spectrum by ...Power Spectrum from Autocorrelation vs. FFT

sample autocorrelation matrix eigenvalues negative

doublehelics - 2011-11-29 04:08:00
Hey all, i am computing sample autocorrelation for some continouous valued data (using this: but the generated correlation matrix has negative eigenvalues. Is there a way to fix the autocorrelation matrix to have non-negative eigenva...sample autocorrelation matrix eigenvalues negative

Autocorrelation matrix of a long sequence

sasuke - 2009-04-16 01:39:00
Hi I am using MATLAB to generate close to 10^8 samples of a Rayleigh fading channel using Jakes method. Once I generate these samples, I have to then create a 20 x 20 autocorrelation matrix. I am using MATLAB to do this. MATLAB works perfectly for 10^6 samples, but once the number of samples incr...Autocorrelation matrix of a long sequence

Is autocorrelation of real sequences an homomorphic system?

2006-07-10 17:22:00
I am working over estimation of fundamental frequency and spectral shift estimation, using autocorrelations and cepstral analysis. The Cepstral analysis is an homomorphic system, is possible to calculate as: X(w) = FFT[ x(n) ] c(n) = IFFT[ log |X(w)| ] The autocorrelation function is possi...Is autocorrelation of real sequences an homomorphic system?

Good reference for pitch tracking by autocorrelation

2005-10-06 05:13:00
Hi. Does anyone have a good reference for pitch tracking by autocorrelation? I do note that there is a very long thread on this topic, but it's too long to follow. So far I've written a very straightforward program to calculate autocorrelation in a signal and also a crude envelope follower to ap...Good reference for pitch tracking by autocorrelation

autocorrelation - HELP!

aron - 2005-03-12 12:36:00
Hi! I am a student who is starting to go over autocorrelation. I am trying to understand this concept. I have read several posts here concerning this topic but I cannot find the answer for my problem. I have to calculate the autocorrelation of the signal at the receiver which is the sum of ...autocorrelation - HELP!

Proof regarding autocorrelation of a pulse in white noise

Craig - 2003-06-30 17:31:00
Let x[n] = s[n] + p[n] where s[n] is complex Gaussian white noise (GWN) and p[n] is a complex signal in the for Ae^{j2pi w + phi} where w is radian frequency and phi is a phase factor. I want to show that if I do the autocorrelation of x[n] (ie x[n]x[n-1]* , where * denotes the complex conj...Proof regarding autocorrelation of a pulse in white noise

Autocorrelation matrix with matlab

thom - 2006-06-29 05:46:00
Hi I would like to compute the autocorrelation matrix from a vector with Matlab. I don't have the statistical signal processing toolbox (I can only use "cov" and "corrcoef" functions, or build my own function). Could someone explain how I can do? Thanks a lot. Thom ...Autocorrelation matrix with matlab


angelredrose - 2008-11-17 11:01:00
Hi, I am trying to understand the autocorrelation function for better timing resolution. I am bit confused how to find out the auto correlation PEAK from the output of M-Sequence? and What is the impact of distance between the two peaks? In other words, the impact of the length of the M-Sequence? ...Autocorrelation

Re: regarding white noise

2005-12-22 15:06:00
> I want to know why white noise floor is added to the autocorrelation > function in the lpc analysis. I'm not an expert with LPC, but I know with adaptive dsp, you need to keep the inverse of the autocorrelation matrix stable. This is especially true with highly self-correlated signals. ...Re: regarding white noise

Re: Newbie, heart data analysis - detecting peaks?

v - 2004-01-13 09:29:00
Hay Datura, this problem is very similar to the CELP coding algorithm stage named "Tone detection and tone period estimation". This procedure is rather robust and is proven in every CELP coder. The idea is to calculate the autocorrelation function for delays which belong to the human pulse pe...Re: Newbie, heart data analysis - detecting peaks?

Re: Convolution and Correlation

Randy Yates - 2003-12-25 12:01:00
Vimal wrote: > Hello all, > > When the two sequances are symmetrical then the correlation and the > convolution are same from the classical definitions. Actually this is true if only one sequence is (even) symmetric. > My query is that, the correlation (if not ergodic) has joint pdf ...Re: Convolution and Correlation

Autocorrelation rocks for Engine RPM

Robert Scott - 2013-06-10 18:12:00
A while ago I posted a question about how to extract pitch information from the messy sound of an engine. It was for an iPhone app I have developed which displays the RPM of an engine based on the sound it makes. Vladimir and other suggested autocorrelation as used in pitch detection in speech...Autocorrelation rocks for Engine RPM


HardySpicer - 2009-08-01 02:32:00
How do I find the autocorrelation of a multivariable channel with 2 outputs? The result will be a matrix of correlation functions which are a function of lag. Suppose the signals are a vector S={s1 s2} I can do R(k+1,lag)=beta*R(k.Lag)+(1-beta)*S(k+1)S^T(k+1+lag) where T is transpose of th...Autocorrelation

Re: Correlation Threshold Meaningful Value

Rune Allnor - 2005-11-25 04:55:00
newsnetstudent wrote: > Hi, > > The autocorrelation of a signal X is generally bell-shaped with maximum > value at the middle. I am just wondering, from what a threshold value we > can assume practically that the signal autocorrelation is null? > > Assume that the maximum value of th...Re: Correlation Threshold Meaningful Value

C6711 DSK, DSPLIB, autocorrelation, double-word aligned?

Joe - 2005-05-30 21:24:00
Hey everybody I am a newbie when it comes to C-programming and DSPs. I have been playing around with the autocorrelation-function that comes with TI's DSPLIB. I have made a small program to see how the autocorrelation-function works. The program compiles without errors but I do not get the ...C6711 DSK, DSPLIB, autocorrelation, double-word aligned?

spreading code with low autocorrelation

Thomas Magma - 2007-08-20 14:25:00
Hello, I'm looking for a spreading code that I can output from a microcontroller (PIC). The sequence must have low autocorrelation with a good merit factor. It should be a long sequence of between 4000 and 20000 and does not have to be done with a LFSR (shift register) since I have lots of ...spreading code with low autocorrelation
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