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Monday, December 13, 2010

MATLAB PROGRAM FOR IMPLEMENTING CIRCULAR CONVOLUTION OF TWO SEQUENCES


function y=circular_convolution(x,h)
x= input ('enter the first sequence');
h= input ('enter the second sequence');
N1= length(x);
N2= length(h);
N=max(N1,N2);%length of sequence
x=[x zeros(1,N-N1)];  %modified first sequence
h=[h zeros(1,N-N2)];  %modified second sequence

for n=0:N-1;
    y(n+1)=0;
    for i=0:N-1
       j=mod(n-i,N);
       y(n+1)=y(n+1)+x(i+1)*h(j+1);  %shifting and adding
    end
end
%to display and plot circular convolution
n=1:N;
disp('output sequence of circular convolution');
disp(y);%to view output in command window
pause;
stem(n,y);%plotting circular convolution
grid minor;
xlabel('time index');
ylabel('amplitude');
title('circular convolution sequence of x and h');
 
 
OUTPUT WAVEFORM 
 

6 comments:

  1. can u explain me how the mod command works for positive and negative values

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    Replies
    1. it is just a remainder value.............there is no sign included

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  2. http://mathforum.org/library/drmath/view/52343.html
    I guess this would give the answer to your query@DHANESHBABU

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  3. This comment has been removed by the author.

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  4. Thanks Quiz Champion. It appears to work fine for short vectors. On the other hand, for huge vectors like those coming from sampling a sound wave at 44.1 kHz the algorithm gets bogged down. Have to use Matlab's cconv in that case. Perhaps an alternative version using indexing might be in order. In any case, an interesting illustration of how the circular convolution is defined.

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  5. Thanks dude.. You're a life saver..

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