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"definition" of CONVOLUTION

I think I'm missing something basic. http://mathworld.wolfram.com/Convolution.html defines convolution as "A convolution is an integral that expresses the amount of overlap of one function g as it is shifted over another function f. ..." So what is difference between convolution and correla...

Re: Multipath Question and OFDM

On Dec 12, 8:19 am, Randy Yates wrote: > > Cyclic convolution? Orthogonalizes the operation? What do these mean? > Is cyclic convolution the same as circular convolution? Cyclic convolution = circular convolution. Recall that the DFT is the correct transform for periodic (circular, c...

Constant in convolution intergal

Convolution between A(t) and S (t) is defined as integral (-infinity to +infinity) with inside integral we have A(T)S(t-T)dT, now suppose if we have A(T)S(vt-vT) inside that intergal, where 'v' is a constant. Can we still call it as a convolution? if yes how can we take care of 'v' and if its...

Re: re:How to perform Convolution in excel?

abariska@student.ethz.ch wrote: > Almost. The convolution of s(n) with y(t) is the inverse FT of the > (point-wise) product of S(f) with Y(f)! With appropriate zeropadding (otherise, this describes circular convolution). ...

Circular convolution to Linear convolution.

Hi, I am new to this programming world, and i really need some serious help. I have done a program in which i design a filter in frequency domain, then i take a CT image, which is a 3d image, read each voxel and make a 1d array. then i equal the number of samples for both the data set. so i have e...

convolution

Hi all, I need to convolve a sine wave with random signal. I made use of the conv function in matlab. I am expecting a dual-dirac histogram for the resulting convolution. But I keep getting the gaussian histogram of the random signal as the result of the convolution. Can anyone suggest a proper c...

Convolution

This is just a curious doubt. What is the statistical significance of convolution? For instance, we define the auto correlation in terms of expectation as R(u) = E(X.Xu). Similarly, do we have any expression for convolution of two signals? Can I have it as something like (sorry, if it is complet...

Please help with Circular Convolution!

Hi everyone, I'm currently a student studying electrical engineering at University so I'm new to both these forums and the subject of DSP in general. I would just like to ask how can I compute the circular convolution of the two sequences: {x(n)} = {4,3,2,1} and {h(n)} = {5,6,7} I know ho...

help! Using discrete convolution to approximate continuous convolution...?

Hi all, I am helping a friend on this. We would like to evaluate the convolution of f(x)=exp(3 * x) / (1 + exp(x) ^ 5). However, in Maple and Mathematica, using symbolic calculations, the convolution results in numerical oscillation (lots of spikeness). We don't know why. We just couldn'...

Convolution Tutorial

I have created a tutorial on the convolution integral. It uses an interactive flash program with embedded audio files. It is located here: http://www.fourier-series.com/Convolution/index.html ...

Want to Understand Convolution

I've looked at the equations for convolution and correlation and, yes, I can work them. And I've heard that common illustration of clapping your hands in an echo chamber. But I just can't get my brain around just what it happening there. Anyone know of a book giving a good intuitive grasp of c...

linear n circular convolution relation

I have the knowledge of fourier transform of the circular convoluion of two vectors say h and s, ie i know FFT (s ** h) [saying ** stands for circular convolution]. I want to know FFT of linear convolution of s and h ie my target is to calculate FFT(s*h) [where * is the linear convolution]. I ne...

Questions about Convolution of Spectra and Matlab 'conv()' function

Hello. I would like to obtain the convolution of two spectra. I have the complex form Fourier coefficients for the first 300 harmonics of each spectra. I was looking at the definition of convolution in one of my books and the sumation term goes from -infinity to infinity. Can I obtain a good a...

FFT convolution giving different results from convolution

I read the chapter about FFT convolution (chapter 18) on dspguide.com and from what I understood, to perform a FFT convolution, you perform a FFT on your filter kernel and on your signal (after you have changed their size and zero padded), you multiply each real and imaginary part of the two sig...

Convolution and Correlation

Hello all, When the two sequances are symmetrical then the correlation and the convolution are same from the classical definitions. My query is that, the correlation (if not ergodic) has joint pdf term in its definition which is not there in convolution. So can I assume that the above defin...

convolution

hi guys.....i am beginner in dsp..... Can somebody tell me the physical meaning of convolution.....wht does it do actually?? ...

How to decide system response using step response?

Hi all, Suppose the forced input to the system is f(t), the step response of the system is a(t) and the output is y(t). Now we want to find y(t), I am confused: Which of the following is the correct output y(t)? (1) y(t)=convolution(differentiate(a(t)), f(t)) and (2) ...

Tutorial on Convolution and FIR Filters

Hi, I have created a three flash program that demonstrate: Discrete convolution Low Pass FIR filters Band Pass FIR filters. It is located here: http://www.fourier-series.com/fourierseries2/convolution.html Brent ...

fastest cyclic convolution algorithm

Hello everyone: First of all, thanks to all those who have posted before and for saving the archives. As you know this is my first post here. I searched the archives by terms and by circular convolution but did not find anything, hope I didn't miss a post. You see, I'm trying to implement a par...

Search for Convolution method in JAVA

Hello! I'm searching for a method/class/package in JAVA that implements a linear convolution algorithm between two signals. For example "public convolution(double[] signal1, double[] signal2)" that convolves signal 1 with 2. I've searched in many webpages, but I've found nothing. I think, I...

help with convolution and product theorem

hi I'm a bit screwed up by the notation used in fourier transform, on convolution and product theorems. I'm drawing a blank with regard to what's the difference between: f1(t)*f2(t) F1(w)F2(w) [convolution theorem] f1(t)f2(t) F1(w)*F2(w) [product theorem] what's the difference betw...

convolution code for matlab

hi.. here i m sending correct convolution code for matlab...%************************************************************************* % Convolution of Two signals %************************************************************************** %DKV clc; close all; clear all;...

Re: Frequency /time domain equalization

Hi, I am capturing that effect by just using circular convolution instead of linear convolution and sending the blocks (packets) independent from each other. Best Regards, -SaiRamesh. ...

Frequency convolution

Hello everyone. I have a question I cant find an answer to: Say you have, X(z) the z transform of a sampled time response x[n], i.e. Z{x[n]} = X(z) Does a Y(z) exist s.t. Z{x[n]^2} = Y(z) and if so, how does it relate to X(z)? If you dont feel challenged enough, try this other one: ...

Convolution

I need to convolve two polynomials which are the same - only one has all its roots outside the unity circle and the other within.eg a(z^-1) =a0+a1z^-1 + a2z^-2 +... with a(z) = a0+a1z+a2z^2+... ie one is causal in terms of z^-1 and the other is in terms of z (or can be interpreted thus). ...

why do we need Polyphase decimatation filter?

I did a decimator FIR filter simply by doing the convolution only once every M' input sample. for example M=3: feed x0,feed x1, feed x2, convolution, feed x3,feed x4, feed x5, convolution, feed x6,.... Then I find many people talk about polyphase decimation filter, I wonder if it is more effi...

circular convolution

I'm perusing the web and I suspect worse case I'll grab a few texts to further assist me, nonetheless, given two sequences ( radar application ) - reference and receive of length 1024. It was explained to me that the for linear convolution, I'll pad the sequences with zeros, then compute the FFT...

Cross-correlation by convolution (unexpected results)

Since an image is word ten thousand words, here's what sums up what i'm trying to do http://www.geocities.com/michel0528/correlation.jpg As you can see, I'm trying to correlate the first signal by the second by correlation. The problem is, I didn't really expect the result you can see on the p...

Java fft (not power of 2)

Hi to all, I've been writing an application in JAVA that uses the Fourier Transform, and performs several operations, such as the convolution. The convolution is being processed in the time domain, so when signals lenths are big (i.e. 1000 values or more), it takes very long to process the con...

Re: efficient inverse fft of a band-pass function

anando wrote: > Hi > > I'd be grateful if somebody could point me to the right literature for the > following problem: > > I have a function r(t) which is known as well as its Fourier transform > R(f). Thus R(f) --> IFFT --> r(t). Both of them are known. > > Now suppose I hav...

DFT circular convolution

hello everybody!! can anyone tell me in calculating circular convolution using DFT what will happen if i use two different length signal? suppose one is of 4 point and the other is of 3 point then what will be the system?i have to do both 4 point DFT?or 4+3-1 or 6 point DFT as like linear con...

Image FFT Convolution - C++/VC++ source code

I'm looking for a simple (need not be very efficient) VC++/C++ library that does the image (png) convolution, 2D FFT. I would like to develop a image search feature (http://www.dspguide.com/ch24/6.htm) with a VC+ + based GUI around it. http://www.codeproject.com/KB/graphics/ImageConvolution.aspx ...

Derivative of convolution

If y = conv(x,w) What is the derivative of y with respect to w ? Here y is the convolution between x and w, all are one dimensional. Thanks This message was sent using the Comp.DSP web interface on www.DSPRelated.com ...

Deconvolution question

Suppose I have an acoustic guitar with a (relatively good-sounding) peizo pickup (a K&K, for those interested). I can mic the guitar and record the peizo simultaneously. But when I deconvolve the miked signal against the peizo, the resulting convolution signature isn't very coherent. Most co...

fastest convolution

Hi, Does anybody have the fastest method (using paper and pencil) to calculate the convolution: y[n]=x[n]*h[n] where x[n]=u[n-3] - u[n-14], h[n]=u[n-5] - u[n-8], where u[n] is the step function, u[n]=1 for n> =0, and u[n]=0 for n ...

why we want to do folding while performing convolution

hi all can u explain in detail why there is need for folding when we perform convolution operation with an (practical)example? thanks in advance sk ...

Re: Need argent help regarding delay estimation

L - 1 > Pxy(n,k) = 1/ L summation x*(n- l -k) y(n - l) > l = 0 > > Can you please help me in this regard Sir. > > _____________________________________ > Do you know a company who employs DSP engineers? > Is it already listed athttp://dsprelated.com/...

Scaling Factor In Approximating Continuous-time Convolution by Discrete-time Convolution

Hello, I know this may sound a common or even a basic question to many, however I will appreciate if someone can give me insight on this. I read some of the older posts on related topics but a fraction of doubt still remains. I am trying to find the correct scaling factor for the output of ...

Why linear convolution in OFDM causes ICI;

Hello group We know that the use of cyclic prefix (CP) in an OFDM turns the linear convolution (between the channel and the transmitted signal) into a circular convolution. This is efficient to do because then we can easily equalize the channel. In most books it is referred that CP combats IS...

Re: Is FFT Overlap-add needed here?

Shafik wrote: > If you dont mind me asking: > > How then, is the FFT used for filtering of images, where the FFT of an > image is taken, modified in the frequency domain, then converted back. > The same is done with time-domain signals as well. > Why is the issue of aliasing not consi...