实验三 信号与系统&Matlab 连续时间信号的频域分析

    clear all
    clc
    m = input('m=');
    t = -2*pi:0.01:2*pi;
    n = round(length(t)/8);
    f = [ones(n,1);-1*ones(n,1);-1*ones(n,1);ones(n,1);ones(n,1);-1*ones(n,1);-1*ones(n+1,1);ones(n,1)];
    y = zeros(m+1,max(size(t)));
    y(m+1,:)=f';
    figure(1);
    plot(t/pi,y(m+1,:));
    grid;
    axis([-2 2 -1.5 1.5]);
    title('周期方波');
    xlabel('单位pi','Fontsize',8);
    x = zeros(size(t));
    kk = '1';
    for k=1:2:2*m-1
    pause;
    x = x+4/pi*cos(k*t)*sin(k*pi/2)/k;
    y((k+1)/2,:) = x; 
    plot(t/pi,y(m+1,:));
    hold on;
    plot(t/pi,y((k+1)/2,:));
    hold off;
    grid;
    axis([-2 2 -1.5 1.5]);
    title(strcat('第',kk,'次谐波叠加'));
    xlabel('单位pi','Fontsize',8);
    kk = strcat(kk,'、',num2str(k+2));
    end
    pause;
    plot(t/pi,y(1:m+1,:));grid;
    axis([-2 2 -1.5 1.5]);
    title('各次谐波叠加波形');
    xlabel('单位pi','Fontsize',8);

    clear all;
    clc
    syms t w;
    f=e
    xp(-2*t)*heaviside(t);
    t1=-2:0.01:2;
    f1=subs(f,t,t1)
    subplot(1,2,1)
    plot(t1,f1)
    title('f(t)')
    F=fourier(f,t,w)
    w1=-2:0.01:2;
    F1=subs(F,w,w1)
    subplot(1,2,2)
    plot(w1,abs(w1))
    title('|F(w)|')

    clear all;
    clc
    syms t w;
    f=exp(-2*abs(t));
    t1=-2:0.01:2;
    f1=subs(f,t,t1)
    subplot(1,2,1)
    plot(t1,f1)
    title('f(t)')
    F=fourier(f,t,w)
    w1=-2:0.01:2;
    F1=subs(F,w,w1)
    subplot(1,2,2)
    plot(w1,abs(w1))
    title('|F(w)|')

    clear all;
    clc
    syms t w;
    f=t.*(t>0.5)-t.*(t>(-1*0.5));
    t1=-6:0.01:6;
    f1=subs(f,t,t1)
    subplot(1,2,1)
    plot(t1,f1)
    title('f(t)')
    F=fourier(f,t,w)
    w1=-2:0.01:2;
    F1=subs(F,w,w1)
    subplot(1,2,2)
    plot(w1,abs(w1))
    title('|F(w)|')

    clear all;
    clc
    syms t w;
    f = (1-abs(t)).*(abs(t)<=1)
    t1=-2:0.01:2;
    f1=subs(f,t,t1)
    subplot(1,2,1)
    plot(t1,f1)
    title('f(t)')
    F=fourier(f,t,w)
    w1=-2:0.01:2;
    F1=subs(F,w,w1)
    subplot(1,2,2)
    plot(w1,abs(w1))
    title('|F(w)|')

    clear all;
    clc
    syms t w;
    f = sin(t)/t;
    t1=-10*pi:0.001:10*pi;
    f1=subs(f,t,t1)
    subplot(1,2,1)
    plot(t1,f1)
    title('f(t)')
    F=fourier(f,t,w)
    w1=-10*pi:0.001:10*pi;
    F1=subs(F,w,w1)
    subplot(1,2,2)
    plot(w1,abs(w1))
    title('|F(w)|')

    syms t w; 
    F=2/(1+w^2) ; 
    f=ifourier(F,t)