%==================================================================
% Name：cconv.m
% The program can be used to compute the convolution 
% of two continuou-time signals.
% please express the signals in terms of the unit step function.
% for example：e(t)=exp(-2*t).*u(t).
%==================================================================
clear;close all;
disp('請將參與卷積運算的信號用單位階躍函數表示出其時間范圍，')
disp('例如：e(t)=exp(-2*t).*u(t)。')
t0=-10;%input('請輸入信號的起始時間（建議取0—-10）：');
t1=10;%input('請輸入信號的終止時間（建議取0—10）：');
p=0.005;
t=t0:p:t1;
x=input('請輸入激勵信號：');
h=input('請輸入系統沖激響應：');
f=p*conv(x,h);             %卷積計算

% 將卷積的結果取得和兩個輸入的信號一樣長，
% 以便在相同的坐標中繪制其圖形并方便比較。
l=length(f);
m=2*t0:p:t0-p;
n=t1+p:p:2*t1;
m1=zeros(1,abs(t0/p));
n1=zeros(1,abs(t1/p));
lm=length(m1);
ln=length(n1);
f=f([lm+1:l-ln]);

clf;
subplot(3,1,1)
plot(t,x);grid on;
title('The input signal e(t)：');
subplot(3,1,2);
plot(t,h,'m');grid on;
text(0.9*t0,0.8*max(h),'The impulse response h(t)：');
subplot(3,1,3);
plot(t,f,'r');%axis([t0,t1,min(f),max(f)]);
text(0.9*t0,0.8*max(f),'The output response r(t)：');
xlabel('time t');grid on;