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# need help - convolution using DFT

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#### kalpana.aravind

##### Junior Member level 3
linear convolution using dft

Hi,

i want to know,

how to do the linear convolution of two sequences,
x1(sinusoid of frequency f1) and x2(sinusoid of frequency f2) using DFT in MATLAB.
please provide any website address where to find the MATLAB code for DFT.
any suggestions welcome.

thanks

matlab code for linear convolution using dft

just go to matlabcentral.com n search for DFT u will see a huge database of codes...

### kalpana.aravind

Points: 2
convolution using dft

Linear convolution of 2 arbitrary non-finite discrete-time sequences in Matlab is usually done using the function conv(a,b), where a,b - operands of convolution. It's not difficult to notice, that this computation is absolutely equivalent to polynomial multiplication (the coefficients of these polynomials are places in the row vectors a and b).

DFT is not exactly the linear convolution, it's the circular convolution. The main differences between these 2 types of convolution is the size of the final vector. Provided you evaluate the circular one it's equal to the size of the vectors, whereas concerning the linear one it's equal to length(a)+length(b)-1.

With respect,

Dmitrij

dft convolution

do search in mathworks.com

there are many applications over there...
u will surely get the code for convolution as well as DFT

types of convolution

i wrote one dft code