How can I Implement a convolution function in MATLAB and perform it on the following signals and plot the results ?
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Vaban Dust
le 14 Mar 2018
Commenté : Walter Roberson
le 29 Déc 2021
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.
2 commentaires
Réponse acceptée
Abraham Boayue
le 16 Mar 2018
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);
3 commentaires
Niklas Endler
le 20 Oct 2020
Correct me if I'm wrong but this only works in cases where the step function h[m] is symmetric?
Walter Roberson
le 20 Oct 2020
discrete convolution and discrete filtering are the same mathematical operation, but they use the opposite convention on whether the matrix is applied left-to-right or right-to-left.
>> conv([1 2 3],[1 2 3])
ans =
1 4 10 12 9
>> conv([1 2 3],fliplr([1 2 3]))
ans =
3 8 14 8 3
conv() essentially flips the second vector and moves the result from left to right across the first vector; assume that there are zeros outside the first vector. This operation is thematically consistent with continuous convolution,
as opposed to ![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/386793/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/386788/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/386793/image.png)
Plus de réponses (3)
Ankur Agrawal
le 21 Sep 2021
Modifié(e) : Walter Roberson
le 29 Déc 2021
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;
0 commentaires
Abdullah Mohmmed
le 29 Déc 2021
Write a MATLAB code to calculate and plot the two-sided convolution between the two discrete time signals x(n) and h(n) shown below
1 commentaire
Walter Roberson
le 29 Déc 2021
No signal definitions were shown.
And if they had been, we would have just referred you to the discussion above, which includes full code.
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