MATLAB: How tomplement a convolution function in MATLAB and perform it on the following signals and plot the results

convolution

Hi guys,
I have the following function:
impulse_response = zeros(1, length(input) + length(delta) - 1 );
for t_samp = 1:length(input)
for c_samp = 1:length(delta)
   index = t_samp + c_samp - 1;
value = delta(c_samp) * input(t_samp);
impulse_response(index) = impulse_response(index) + value;
end
end
I am new to Matlab and I want to understand how to Implement a convolution function in MATLAB and perform it on the following signals and plot the results ?
Task (1):
x[n] = [1,1,1,1] h[m] = [1,0,−1] x[n] = sin(n) h[m] = [−1,−2,8,−2,−1] 20 ≤ n < 20
Task (2): Given the input signal x[n]=0.3∗sin(n/5)+sin(n/50) : -Create your own delta signal h[m] that removes the higher frequency sinusoidal component to get yl[n].
Thanks in advance for your kind explanation.

Best Answer

Hey Vaban, you already got a code that implements convolution in matlab, all you need to do is to use it to solve your exercises: Alternatively, you could use matlab built in function called conv(), but it seems like your teacher wants you to learn how to code in matlab. Here is how you can use the code you have. Ex. Task 1.
% This is just a cleaner code, same as the one you posted
clear variables
close all
n = -20:20;
x = sin(n);            
h = [-1,-2,8,-2,-1];  
N = length(x);
M = length(h);
Ny = N + M -1;
y = zeros(1,Ny);
for i = 1:N
      for k = 1:M
       y(i+k-1) = y(i+k-1) + h(k)*x(i);
      end
end
m = 0: Ny-1;
% Make plot
figure
stem(m,y,'linewidth',3,'color','m')
grid;
a = title('Output of an LTI System y(n)');
set(a,'fontsize',14);
a = ylabel('y(n)');
set(a,'Fontsize',14);
a = xlabel('n');
set(a,'Fontsize',14);
% Using matlab built in function (you get the same results)
figure
y2 = conv(x,h);
stem(m,y2,'linewidth',3,'color','r')
grid;
a = title('Output y(n) using conv(x,h)');
set(a,'fontsize',14);
a = ylabel('y(n)');
set(a,'Fontsize',14);
a = xlabel('n ');
set(a,'Fontsize',14);
% % input = [1 1 1 1]; % input = x (n) = [1 1 1 1]
% % delta = [1 0 -1];  % h(m) = [-1 0 1]
% impulse_response = zeros(1, length(input) + length(delta) - 1 );
% for t_samp = 1:length(input)
% for c_samp = 1:length(delta)
%      index = t_samp + c_samp - 1;
%      value = delta(c_samp) * input(t_samp);
%      impulse_response(index) = impulse_response(index) + value;
% end

% end
% Ny = length(input) + length(delta)-1;
% y =  impulse_response;
% m = 0:Ny-1;
% % plot
% stem(m,y,'linewidth',3,'color','b')
% grid;
% a = title('Output of an LTI System y(n)');
% set(a,'fontsize',14);
% a = ylabel('y(n)');
% set(a,'Fontsize',14);

% a = xlabel('n [1 4]');
% set(a,'Fontsize',14);
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