高频电子线路Matlab仿真实验

1.仿真题目

（1）线性频谱搬移电路仿真

根据线性频谱搬移原理，仿真普通调幅波。

基本要求：载波频率为8kHz，调制信号频率为400Hz，调幅度为0.3；画出调制信号、载波信号、已调信号波形，以及对应的频谱图。

扩展要求1：根据你的学号更改相应参数和代码完成仿真上述仿真；载波频率改为学号的后5位，调制信号改为学号后3位，调幅度设为最后1位/10。（学号中为0的全部替换为1，例如学号**********，则载波为*****Hz，调制信号频率为114，调幅度为0.4）。

扩展要求2：根据扩展要求1的条件，仿真设计相应滤波器，并获取DSB-SC和SSB的信号和频谱。

（2）调频信号仿真

根据调频原理，仿真调频波。

基本要求：载波频率为30KHz，调制信号为1KHz，调频灵敏度，仿真调制信号，瞬时角频率，瞬时相位偏移的波形。

扩展要求：调制信号改为1KHz的方波，其它条件不变，完成上述仿真。

2.说明

（1）仿真的基本要求每位同学都要完成，并且记入实验基本成绩。

（2）扩展要求可以选择完成。

1.0

>> ma = 0.3;

>> omega_c = 2 * pi * 8000;

>> omega = 2 * pi * 400;

>> t = 0 : 5 / 400 / 1000 : 5 / 400;

>> u_cm = 1;

>> fc = cos(omega_c * t);

>> fa = cos(omega * t);

>> u_am = u_cm * (1 + fa).* fc;

>> U_c =fft(fc,1024);

>> U_o =fft(fa,1024);

>> U_am =fft(u_am, 1024);

>> figure(1);

>> subplot(321);plot(t, fa, 'k');title('调制信号');grid;axis([0 2/400 -1.5 1.5]);

>> subplot(323);plot(t, fc, 'k');title('高频载波');grid;axis([0 2/400 -1.5 1.5]);

>> subplot(325);plot(t, u_am, 'k');title('已调信号');grid;axis([0 2/400 -3 3]);

>> fs = 5000;

>> w1 = (0:511)/512*(fs/2)/1000;

>> subplot(322);plot(w1, abs([U_am(1:512)']),'k');title('调制信号频谱');grid;axis([0 0.7 0 500]);

>> subplot(324);plot(w1, abs([U_c(1:512)']),'k');title('高频载波频谱');grid;axis([0 0.7 0 500]);

>> subplot(326);plot(w1, abs([U_am(1:512)']),'k');title('已调信号频谱');grid;axis([0 0.7 0 500]);

1.1

>> ma = 0.8;

>> omega_c = 2 * pi * 11138;

>> omega = 2 * pi * 138;

>> t = 0 : 5 / 400 / 1000 : 5 / 400;

>> u_cm = 1;

>> fc = cos(omega_c * t);

>> fa = cos(omega * t);

>> u_am = u_cm * (1 + fa).* fc;

>> U_c =fft(fc,1024);

>> U_o =fft(fa,1024);

>> U_am =fft(u_am, 1024);

>> figure(1);

>> subplot(321);plot(t, fa, 'k');title('调制信号');grid;axis([0 2/400 -1.5 1.5]);

>> subplot(323);plot(t, fc, 'k');title('高频载波');grid;axis([0 2/400 -1.5 1.5]);

>> subplot(325);plot(t, u_am, 'k');title('已调信号');grid;axis([0 2/400 -3 3]);

>> fs = 5000;

>> w1 = (0:511)/512*(fs/2)/1000;

>> subplot(322);plot(w1, abs([U_am(1:512)']),'k');title('调制信号频谱');grid;axis([0 0.7 0 500]);

>> subplot(324);plot(w1, abs([U_c(1:512)']),'k');title('高频载波频谱');grid;axis([0 0.7 0 500]);

>> subplot(326);plot(w1, abs([U_am(1:512)']),'k');title('已调信号频谱');grid;axis([0 0.7 0 500]);

2

>> kf = 2 * pi * 3000;

>> omega_c = 2 * pi * 30000;

>> omega = 2 * pi * 1000;

>> t = -4*pi/omega : 1/30000/100 : 4*pi/omega;

>> fx = cos(omega * t);

>> dOmega = omega_c + kf * cos(omega * t);

>> dFi = kf /(omega) * sin(omega * t);

>> Ucm = 1;

>> Ufm = Ucm * cos(omega_c * t + dFi);

>> subplot(411);plot(t, fx, 'k');title('u_{\\Omega}(t)');grid;axis([0 4*pi/omega -1.5 1.5]);

>> subplot(412);plot(t, dOmega, 'k');title('\\Omega(t)');grid;axis([0 4*pi/omega omega_c-1.1*kf omega_c+1.1*kf]);

>> subplot(413);plot(t, dFi, 'k');title('\\Delta\\phi(t)');grid;axis([0 4*pi/omega -4 4]);

>> subplot(414);plot(t, Ufm, 'k');title('u_{FM}(t)');grid;axis([0 4*pi/omega -1.5 1.5]);

2.1

kf = 2 * pi * 3000;

omega_c = 2 * pi * 30000;

omega = 2 * pi * 1000;

t = -4*pi/omega : 1/30000/100 : 4*pi/omega;

fx = square(omega * t);

dOmega = omega_c + kf * fx;

temp = sawtooth(omega * t, 0.5);

dFi = kf /(omega) * temp;

Ucm = 1;

Ufm = Ucm * cos(omega_c * t + dFi);

subplot(411);plot(t, fx, 'k');title('u_{\\Omega}(t)');grid;axis([0 4*pi/omega -1.5 1.5]);

subplot(412);plot(t, dOmega, 'k');title('\\Omega(t)');grid;axis([0 4*pi/omega omega_c-1.1*kf omega_c+1.1*kf]);

subplot(413);plot(t, dFi, 'k');title('\\Delta\\phi(t)');grid;axis([0 4*pi/omega -4 4]);

subplot(414);plot(t, Ufm, 'k');title('u_{FM}(t)');grid;axis([0 4*pi/omega -1.5 1.5]);