# Questions tagged [correlation]

Correlation or Cross-Correlation is a measure of similarity of two waveforms as a function of a time-lag applied to one of them.

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### Why we need convolution in image processing?

To my understanding, there are two methods to do linear filtering. One is cross-correlation, and another is convolution. Convolution requires 'flipping' the kernel when you do the calculation. I think ...
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### What exactly happens in correlation?

I have understood convolution and it seems almost same as correlation mathematical expression wise. But in terms of signal processing,both are different operations. The difference between convolution ...
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### The difference between convolution and cross-correlation from image processing point of view

The difference between convolution and cross-correlation from a signal-analysis point of view The above question gives very good information from signal processing point of view. But what about images?...
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### Extract a signal from noise, so I can view noise spectrum only?

I have a perfect modulated signal. I have the same signal but with noise, this noise is from non linear amplification. Is it possible, to extract the clean signal so it's just leaving the noise? The ...
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### Autocorrelation & Cross-Correlation -> Main uses in DSP??

Please help understanding the DSP usage of Autocorrelation & Cross-correlation It seems this is strongly linked to calculating phase offsets, frequency offset for carrier recovery, symbol timing ...
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### Power spectral density and auto correlation function: Frequency vs time representation

I have a time correlated periodic signal $a(t)$ with $t=0,1,...,T$ and $a(t+T) = a(t)$ that has been sampled at rate $\Delta t$ and I analyse the signal using the PSD via FFT and the ACF. As far as I ...
1 vote
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### Cross-correlation maximum in frequency domain

I need to compute the complex cross-correlation between two signals a and b and the take only the maximum value of the cross-correlation, regardless of the lag time where this occurs. I can do it ...
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### Given a correlation between A and B, can I calculate bounds on the correlation between A and C times A and B?

Lets say I have three vectors, A, B, and C. I know the correlation between A and B, which makes it intuitive that this gives a bound on the product of the correlations $r_{B,C} \cdot r_{A,C}$. For ...
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### NaN values with correlation metrics

I am using the Peak to Correlation Energy (PCE) Metric to measure the similarity between two images using MATLAB. In some cases, the PCE value obtained is NaN. How can I solve this problem?
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### How to measure correlation between 1 bit samples and theoretical original waveform?

I'm investigating quantization error. I have an analogue waveform that looks like this and is of theoretically infinite resolution:- I've sampled it as (8 bit oscilloscope readings & 0b1) to ...
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### Linear correlation of two vectors?

We had a lecture on digital watermark detection using linear correlation. Here it was explained that the linear correlation of two vectors is equal to their scalar product divided by the dimension. So,...
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### Comparing two small audio files (e.g., hand clap) Android

Dears, I am new in signal processing and I am dealing with an Android application that should do some audio files (having the same "small" duration) comparison in real time. My main focus is ...
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### Is there any way to align temporally two signals in spectrogram?

I am keen to know that If I have two signals say : Farend_signal (y[n]) and Nearend_signal (x[n]) and x[n] also contains an echo of y[n] with some delay. Is there any technique to align these two ...
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### Applying Circular Cross Correlation in MATLAB

I have searched Google for circular cross correlation using Matlab, and I have found it only for one dimensional signals. Could you please help me implementing circular cross correlation between two ...
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### Spatial multiplexing MIMO, antenna critical spacing, antenna isolation

How does antenna isolation affect single user spatial multiplexing MIMO performance in an antenna array? Text books talk about a critical antenna spacing of 1/2 of the wavelength provided that the ...
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### nature of output of the addition of white noise with colord noise

I want to know that the addition of a uncorrelated time series x with a correlated time series, say y generates a time series ...
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### Proving that FFT (and by extension any correlation based estimator) is unbiased

I have a pretty simple question which i should have been able to answer. Just wanted to check if people here have a better solution to it. I am trying to establish that FFT as a frequency estimator (...
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### Comparing mechanical signals with different length

I couldn't find any solution for this that would work for me I'm working in python. I have two similar signals that I can plot Force x Angle. (problem simplified) One plot (angle x force) has length ...
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### How does Correlation for 1D Signals work?

On page 2 of the slide, I don't understand the example. Like $j$ and $s$ are both on the x-axis, what does j+s mean? The filter is $(f(−1), f(0), f(1)) = (−0.5, 0, 0.5)$. How can we use it? Could ...
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### correlation matrix vs. correlation function?

Can someone help me understand the difference between a 1-dim autocorrelation function and a 2-dim autocorrelation matrix of a random process aka time series? My Leon-Garcia textbook defines CX(τ) and ...
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### Are ACF plots sufficient to detect white noise assuming probable existence of non linear associations?

ACF plots use autocorrelations tests to determine associations in time series. Autocorrelations, however, only measure linear associations. To my understanding, certain non-linear associations can ...
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### How does DCT decorrelate images?

I've read in multiple places that DCT decorrelates Toeplitz matrices and images usually have Toeplitz structure. Can you explain with an example how DCT decorrelates a Toeplitz matrix? Example for DFT:...
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### packet encoder RF packets by using LPF for determining if it's zero or one [closed]

I'm transmitting RF packets with frequency 868MHZ , symbol rate (it's the same as bit rate) is 50KBaud , and Im sampling them by a dongle (fs=20480KHZ) to capture those RF packets, the captured ...
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### Deciding if the received packet is valid or not valid [closed]

I have sampled RF wireless packets as IQ samples file, those RF packets has patterns like preamable|syncword|data|crc , I'm doing cross correlation with my constant syncword (after I did the ...
1 vote
I am trying to create a non-i.i.d channel: correlated Rayleigh fading channel. $$H= R_H \cdot H_o,$$ where $H_o$ is i.i.d. channel ( uncorrelated) and $R_H$ is a channel correlation matrix, is ...