1、用MATLAB命令函数分别绘出抽样信号、矩形脉冲信号、周期矩形脉冲信号、三角波脉冲信号、三角波周期信号的波形，理解其中参数的意义。

t=-20:0.01:20;f10=sinc(t);f20=rectpuls(t,2);f30=square(t,2);f40=tripuls(t,0.5);f50=sawtooth(t,0.5);subplot(5,1,1);plot(t,f10);axis([-10,10,-2,2]);subplot(5,1,2);plot(t,f20);axis([-10,10,-2,2]);subplot(5,1,3);plot(t,f30);axis([-10,10,-2,2]);subplot(5,1,4);plot(t,f40);axis([-10,10,-2,2]);subplot(5,1,5);plot(t,f50);axis([-10,10,-2,2]);t=-20:0.01:20;f20=rectpuls(t,2);f21=rectpuls(t,4);f22=rectpuls(t,8);f23=rectpuls(t,16); f24=rectpuls(t,32); subplot(5,1,1);plot(t,f20);axis([-10,10,-2,2]); subplot(5,1,2);plot(t,f21);axis([-10,10,-2,2]); subplot(5,1,3);plot(t,f22);axis([-10,10,-2,2]); subplot(5,1,4);plot(t,f23);axis([-10,10,-2,2]); subplot(5,1,5);plot(t,f24);axis([-18,18,-2,2]);m=5/pi;t=-20:0.0001:20;f30=square(t,4*pi); f31=square(t,8*pi); f32=square(t,16*pi); f33=square(m*t,25); f34=square(m*t,50); subplot(5,1,1);plot(t,f30);axis([-10,10,-2,2]); subplot(5,1,2);plot(t,f31);axis([-10,10,-2,2]); subplot(5,1,3);plot(t,f32);axis([-10,10,-2,2]); subplot(5,1,4);plot(t,f33);axis([-10,10,-2,2]); subplot(5,1,5);plot(t,f34);axis([-10,10,-2,2]);t=-20:0.01:20;f40=tripuls(t,2);f41=tripuls(t,4);f42=tripuls(t,8);f43=tripuls(t,16);f44=tripuls(t,32); subplot(5,1,1);plot(t,f40);axis([-10,10,-2,2]); subplot(5,1,2);plot(t,f41);axis([-10,10,-2,2]); subplot(5,1,3);plot(t,f42);axis([-10,10,-2,2]); subplot(5,1,4);plot(t,f43);axis([-10,10,-2,2]); subplot(5,1,5);plot(t,f44);axis([-18,18,-2,2]);m=5/pi;t=-20:0.0001:20;f50=sawtooth(t,0.25);f51=sawtooth(t,0.5);f52=sawtooth(t,0.75);f53=sawtooth(m*t,0.25); f54=sawtooth(m*t,0.75);subplot(5,1,1); plot(t,f50);axis([-10,10,-2,2]); subplot(5,1,2); plot(t,f51);axis([-10,10,-2,2]); subplot(5,1,3); plot(t,f52);axis([-10,10,-2,2]); subplot(5,1,4); plot(t,f53);axis([-10,10,-2,2]); subplot(5,1,5); plot(t,f54);axis([-10,10,-2,2]);2、分别用MATLAB 的数值运算和符号运算功能，绘出下列连续时间信号的波形。

(1) f (t )=(2−e −2t )u (t ) (2) f (t )=cos (πt2)[u (t )−u (t −4)](3) f (t )=e t cos (t )u (t ) (4) f (t )=23t u (t +2)f=sym('(2-exp(-2*t))*heaviside(t)'); ezplot(f,[-1,10]);t=-1:0.01:10;t1=-1:0.01:-0.01;t2=0:0.01:10;f1=[zeros(1,length(t1)),ones(1,length(t2))]; f=(cos(pi*t/2))*f1;plot(t,f)axis([-1,10,0,2.1])f=sym('cos(pi*t/2)*(heaviside(t)-heaviside(t-4))'); ezplot(f,[-2,10]);t=-1:0.01:10;f1=stepfun(t,0)-stepfun(t,4);f=(cos(pi/2*t)).*f1;plot(t,f)axis([-2,10,-1.1,1.1]);f=sym('exp(t)*cos(t)*heaviside(t)'); ezplot(f,[-2,10]);t=-2:0.01:10;f1=stepfun(t,0);f=(exp(t).*cos(t)).*f1;plot(t,f)axis([-2,10,-7000,1100]);f=sym('2/3*t*heaviside(t+2)'); ezplot(f,[-10,10]);t=-10:0.001:10;f1=stepfun(t,-2);f=2/3.*t.*f1;plot(t,f);axis([-10,10,-2,7]);3、已知信号f(t )的波形如右图所示，绘出满足下列要求的信号波形。

(1) f(−t)(2) f(t−2)(3) f(at) (其中a的值分别取0.5和2)(4) f(0.5t+1)1syms t y;f=sym('2*heaviside(t)-heaviside(t-1)-heaviside(t-2)');f1=subs(f,t,-t);subplot(2,1,1);ezplot(f,[-3,3]);subplot(2,1,2);ezplot(f1,[-3,3]); f(t)t22112yms t y;f=sym('2*heaviside(t)-heaviside(t-1)-heaviside(t-2)'); f1=subs(f,t,t-2);subplot(2,1,1);ezplot(f,[-3,6]);subplot(2,1,2);ezplot(f1,[-3,6]);3syms t y;f=sym('2*heaviside(t)-heaviside(t-1)-heaviside(t-2)'); f1=subs(f,t,0.5*t);f2=subs(f,t,2*t);subplot(3,1,1);ezplot(f,[-3,6]);title('f(t)');subplot(3,1,2);ezplot(f1,[-3,6]);title('f(0.5t)');subplot(3,1,3);ezplot(f2,[-3,6]);title('f(2t)');4syms t y;f=sym('2*heaviside(t)-heaviside(t-1)-heaviside(t-2)'); f1=subs(f,t,(0.5*t)+1);subplot(2,1,1);ezplot(f,[-3,3]);title('f(t)');subplot(2,1,2);ezplot(f1,[-3,3]);title('f(0.5t+1)');4、利用MATLAB画出复信号f(t)=2e j(t+π4)的实部、虚部、模和辅角。

cleart=-10:0.001:10;f=2*exp(j*(t+pi/4)); t_real=real(f);t_imag=imag(f);t_range = abs(f);t_angle = angle(f); subplot(2,2,1);plot(t,t_real);title('real');grid on;subplot(2,2,2);plot(t,t_imag)title('imag');grid on;subplot(2,2,3);plot(t,t_range);title('rang');grid on;subplot(2,2,4);plot(t,t_angle);title('angle');grid on;。