75fd869e2090f3f2f1cadd93c573c644.docx

1、第二章1.(1)t = 0:0.01:5;y = 2 * cos(3 * t + pi / 4);plot(t,y)grid onxlabel(t),ylabel(y)title(y = 2 * cos(3 * t + pi / 4)axis(0 5 -2.5 2.5); (2)t = -1:0.01:5;y = (2 - exp(-t) .* (t=0);plot(t,y)grid onxlabel(t),ylabel(y)title(y = (2 - exp(-t)*(t =0)axis(-1 5 -0.5 2.5); (3)t = -1:0.01:5;y = t .* (t=0) - (

2、t-1)=0);plot(t,y)grid onxlabel(t),ylabel(y)title(y = t .* (t=0) - (t-1)=0)axis(-1 5 -0.5 1.5); (4)t = -1:0.01:5;y = (1 + cos(pi * t).* (t=0) - (t-2)=0);plot(t,y)grid onxlabel(t),ylabel(y)title(y = (1 + cos(pi * t).* (t=0) - (t-2)=0)axis(-1 5 -0.5 2.5); 2.（1）t = -4:0.01:10;a = pi / 4;b = pi / 2;y = 2

3、 + exp(a * i) * t) + exp(b * i) * t);subplot(2,2,1);plot(t,real(y);title(实部);axis(-4 10 0 4.5);grid on;subplot(2,2,2);plot(t,imag(y);title(虚部);axis(-4 10 -3 4);grid on;subplot(2,2,3);plot(t,abs(y);title(模);axis(-4 10 0 4.5);grid on;subplot(2,2,4);plot(t,angle(y);title(相角);axis(-4 10 -1.5 1);grid on;

4、 (2)t = -4:0.01:10;k = 2;b = pi / 4;y = k * exp(t+ b * i) * i);subplot(2,2,1);plot(t,real(y);title(实部);axis(-4 10 -2 2);grid on;subplot(2,2,2);plot(t,imag(y);title(虚部);axis(-4 10 -3 4);grid on;subplot(2,2,3);plot(t,abs(y);title(模);axis(-4 10 0 2);grid on;subplot(2,2,4);plot(t,angle(y);title(相角);axis

5、(-4 10 -4 4);grid on; 3.P = 2 * pi;t = 0:0.01:5;y = square(P * t,50);plot(t,y)grid on;axis(0 6 -2 1.5);title(幅度为1、周期为1,、占空比为0.5的周期矩形脉冲信号) 第三章1.(1)t = 0:0.01:5;y = exp(-t) .* sin(10 * pi * t) + exp(-1/2 * t) .* sin(9 * pi * t);plot(t,y)grid on;title(y = exp(-t) .* sin(10 * pi * t) + exp(-1/2 * t) .*

6、sin(9 * pi * t)axis(0 5 -2 2) (2)t = 0:0.01:5;y = sinc(t).*cos(10 * pi *t);plot(t,y)grid on;title(y = sinc(t).*cos(10 * pi *t)axis(0 5 -1.5 1.5) 2.定义一个函数function f = fun( t )f = (t+1).*(heaviside(t+2)-heaviside(t+1) + heaviside(t+1) + heaviside(t)- heaviside(t-1) - heaviside(t-2) + (1-t).*(heaviside

7、(t-1)-heaviside(t-2);end 调用这个函数t = -2:0.01:6;f1 = fun(t-1);f2 = fun(2-t);f3 = fun(2*t+1);f4 = fun(4-t/2);f5 = (fun(t) + fun(-t) .* (t=0);subplot(231);plot(t,f1);title(f(t-1);axis(-2 6 -2 4);grid onsubplot(232);plot(t,f2);title(f(2-t);axis(-2 6 -2 4);grid on;subplot(233);plot(t,f3);title(f(2t+1);axis

8、(-3 4 -2 4);grid on;subplot(234);plot(t,f4);title(f(4-t/2);axis(-1 8 -2 4);grid on;subplot(235);plot(t,f5);title(f(t)+f(-t)u(t);axis(-3 5 -2 4);grid on; 3t = 0:0.01:3;f = (heaviside(t) - heaviside(t-2).*(1-t);f1 = fliplr(f);fe = (f+f1)/2;fo = (f-f1)/2;subplot(1,2,1);plot(t,fe);title(fe);grid on;subp

9、lot(1,2,2);plot(t,fo);title(fo);grid on; 第四章1.dt =0.001;t=-1:dt:3.5;xt1 = heaviside(t)-heaviside(t-2);xt2 = heaviside(t) + heaviside(t-1) - heaviside(t-2) - heaviside(t-3);f = conv(xt1,xt2)*dt;n = length(f);tt = (0:n-1)*dt-2;plot(tt,f);grid on 第五章1.(1)dt = 0.01;t = 0:dt:4;f = heaviside(t);sys = tf(1

10、,1,4,3);y = lsim(sys,f,t);plot(t,y),grid onxlabel(t),ylabel(y(t)title(零状态响应) (2).dt = 0.01;t = 0:dt:4;f = exp(-t).*heaviside(t);sys = tf(1,3,1,4,4);y = lsim(sys,f,t);plot(t,y),grid onxlabel(t),ylabel(y(t)title(零状态响应) 2.（1）t = 0:0.001:4;sys = tf(1,1,3,2);h = impulse(sys,t);g = step(sys,t);subplot(1,2

11、,1);plot(t,h);xlabel(t),ylabel(h(t);title(冲激响应);grid onsubplot(1,2,2);plot(t,g);xlabel(t),ylabel(g(t);title(阶跃响应);grid on （2）t = 0:0.001:4;sys = tf(1,0,1,2,2);h = impulse(sys,t);g = step(sys,t);subplot(1,2,1);plot(t,h);xlabel(t),ylabel(h(t);title(冲激响应);grid onsubplot(1,2,2);plot(t,g);xlabel(t),ylabe

12、l(g(t);title(阶跃响应);grid on 第六章1 T=2所以函数傅里叶级数为 fx=12+42(cost+132cos3t+152cos5t+.)注意：以下代码需在MATLAB中运行才有多个图，在Word里运行只有一个图t=-5:0.001:5;omega=pi;y=1/2+1/2*sawtooth(2*pi*1/2*(t+1),0.5);plot(t,y);axis(-5,5,-0.3,1.1);grid on;xlabel(t),ylabel(y);title(周期三角波的信号)n_max=1 3 5 9 13;N=length(n_max);for k=1:Nn=1:2:n

13、_max(k);b=4./(pi*pi*n.*n);x=1/2+b*cos(omega*n*t);figure;plot(t,y);hold on;plot(t,x);hold off;xlabel(t),ylabel(部分和的波形)axis(-5,5,-0.3,1.1),grid ontitle(最大谐波数=,num2str(n_max(k)end 2r代表宽度，T代表周期三角信号的傅里叶系数为A*Sa(2*pi/T)n = -30:30;T = 2;w1 = 2*pi/T;f = sinc(n*pi);subplot(311);stem(n*w1,f);axis(-20 20 -1 2);

14、grid on;title(r=T=2) n = -30:30;T = 8;w1 = 2*pi/T;f = sinc(n*pi);subplot(312);stem(n*w1,f);axis(-20 20 -1 2);grid on;title(r=T=8) n = -30:30;T = 16;w1 = 2*pi/T;f = sinc(n*pi);subplot(313);stem(n*w1,f);axis(-20 20 -1 2);grid on;title(r=T=16) 第七章1.（1）f = sym(sin(2*pi*(t-1)/(pi*(t-1);Fw = simplify(four

15、ier(f);subplot(2,1,1);ezplot(abs(Fw);grid on;axis(-4 4 -1 2);title(幅度谱)phase = atan(imag(Fw)/real(Fw);subplot(2,1,2);ezplot(phase);grid on;title(相位谱) 警告: Support of character vectors that are not valid variable names or define a number will be removed in a future release. To create symbolic expressi

16、ons, first create symbolic variables and then use operations on them. In symconvertExpression (line 1559) In symconvertChar (line 1464) In symtomupad (line 1216) In sym (line 179)Fw Fw =-exp(-w*1i)*(heaviside(w - 2*pi) - heaviside(w + 2*pi) (2)fs = sinc(pi*t);f = sym(fs2);Fw = simplify(fourier(f)sub

17、plot(2,1,1);ezplot(abs(Fw);grid on;axis(-4 4 -1 2);title(幅度谱)phase = atan(imag(Fw)/real(Fw);subplot(2,1,2);ezplot(phase);grid on;title(相位谱) 警告: Support of character vectors that are not valid variable names or define a number will be removed in a future release. To create symbolic expressions, first

18、 create symbolic variables and then use operations on them. In symconvertExpression (line 1559) In symconvertChar (line 1464) In symtomupad (line 1216) In sym (line 179)Fw =-2*pi*dirac(2, w)2.(1)syms t;Fw = sym(10/(3+j*w)-4/(5+j*w);ft = simplify(ifourier(Fw,t)ezplot(ft),grid on 警告: Support of charac

19、ter vectors that are not valid variable names or define a number will be removed in a future release. To create symbolic expressions, first create symbolic variables and then use operations on them. In symconvertExpression (line 1559) In symconvertChar (line 1464) In symtomupad (line 1216) In sym (l

20、ine 179)ft =-(exp(-(t*5i)/j)*(sign(imag(1/j) - sign(t)*(5*exp(t*2i)/j) - 2)*1i)/j(2)syms tFw = sym(exp(-4*w2);ft = simplify(ifourier(Fw,t)ezplot(ft),grid on 警告: Support of character vectors that are not valid variable names or define a number will be removed in a future release. To create symbolic e

21、xpressions, first create symbolic variables and then use operations on them. In symconvertExpression (line 1559) In symconvertChar (line 1464) In symtomupad (line 1216) In sym (line 179)ft =exp(-t2/16)/(4*pi(1/2)3.dt = 0.01;t=-2:dt:2.5;f = (heaviside(t+2)-heaviside(t+1).*(t+2)+heaviside(t+1)-heavisi

22、de(t-1)+(heaviside(t-1) - heaviside(t-2).*(2-t);N = 100;k = -N:N;W = pi*k/(N*dt);Fw = f*exp(-i*t*W)*dt;plot(W,abs(Fw);grid on;axis(-5*pi 5*pi -0.1 4);title(频谱图) 4.由题可知，两个门函数完全相同，才能得到三角形脉冲首先将门函数进行时域卷积运算，再将卷积后的结果做傅里叶变换，源程序如下：dt = 0.01;t = -2:dt:2.5;f1 = heaviside(t+0.5)-heaviside(t-0.5);%定义一个门函数f = co

23、nv(f1,f1)*dt;%卷积运算ft = sym(f);Fw = fourier(ft)%对卷积运算所得结果进行傅里叶变换 Fw =pi*dirac(1, w)*2i 再求出一个门函数进行傅里叶变换，再与自身相乘，如果下面所得结果与上述Fw相同，说明验证了傅里叶变换的时域卷积定理，源程序如下：dt = 0.01;t = -2:dt:2.5;f1 = heaviside(t+0.5)-heaviside(t-0.5);ft = sym(f1);Fw1 = fourier(ft);Fw = Fw1*Fw1 Fw =4*pi2*dirac(1, w)2 第八章1.由图可知，该电路频率响应为H(w

24、) = jw/(0.2(jw)3+0.2(jw)2+jw)w = -6*pi: 0.01: 6*pi;b = 10 0;a = 2 2 10 0;H = freqs(b,a,w);subplot(2,1,1);plot(w,abs(H);grid on;xlabel(omega(rad/s),ylabel(|H(omega)|); title(电路系统的幅频特性)subplot(2,1,2);plot(w,angle(H);xlabel(omega(rad/s),ylabel(phi(omega); grid on;title(电路系统的相频特性) 2.(1)频率响应为H(w) = jw/(j

25、w+3/2)t = 0:0.01:20;H = (w*j)/(w*j+3/2);f = cos(2*t);y = abs(H)*cos(2*t+angle(H);subplot(211);plot(t,f);grid on;title(激励信号的波形)subplot(212);plot(t,y);grid on;title(稳态响应的波形) （2）t = 0:0.01:20;w1=2;w2=5;H1 = (-1i*w1+2)./(1i*w1)2+2*1i*w1+3);H2 = (-1i*w2+2)./(1i*w2)2+2*1i*w2+3);f = 3+cos(2*t)+cos(5*t);y =

26、 3+abs(H1)*cos(w1*t+angle(H1)+abs(H2)*cos(w2*t+angle(H2);plot(t,y);grid on;title(稳态响应的波形) 第九章1.Ts = 0.00025;dt = 0.0001;t1 = -0.1:dt:0.1;ft = sin(200*pi*t1);subplot(221);plot(t1,ft);grid on;axis(-0.01 0.01 -1.1 1.1);title(f1的信号)N = 100;k = -N:N;W = pi*k/(N*dt);Fw = ft*exp(-i*t1*W)*dt;subplot(222);pl

27、ot(W,abs(Fw);grid on;axis(-5000 5000 -0.1 0.2);title(f1信号的频谱)t2 = -0.1:Ts:0.1;fst =sin(200*pi*t2);subplot(223);plot(t1,ft,:);hold on;stem(t2,fst);grid on;axis(-0.01 0.01 -1.1 1.1);title(抽样后的信号);hold offFsw = fst*exp(-i*t2*W)*Ts;subplot(224);plot(W,abs(Fsw);grid on;axis(-5000 5000 -0.1 0.2);title(抽样信

28、号的频谱) 2.syms t;Sa(t) = sin(t)./t;subplot(211);ezplot(Sa(t);grid on;title(Sa(t)函数的波形)Fw = simplify(fourier(Sa(t);subplot(212);ezplot(abs(Sa(t);grid on;xlabel(omega),ylabel(H(jw);title(Sa(t)的频谱) 由图可知，Sa(t)的频谱大部分集中在0,6之间，所以可设其截至频率Wm=6,因而Ts=pi/6;采用截至频率Wc = 1.2Wm的低通滤波器对抽样信号滤波后重建信号法f(t),并计算重建信号与原Sa(t)信号的绝对误差Wm = 6;Wc = 1.2*Wm;Ts = 0.4;n = -100:100;nTs = n*Ts;fs = sinc(nTs/pi);t = -6:0.1:6;ft = Ts*Wc/pi*fs*sinc(Wc/pi)*(ones(length(nTs),1)*t)-nTs*ones(1,length(t);t1 = -6:0.1:6;f1= sinc(t1/pi);subplot(311);plot(t1,f1,:),hold on;stem(nTs,fs);axis(-6 6 -1 1);xlabel(nTs