武汉理工大学——通信原理实验报告调试图以及实验代码.pdf
版权申诉
5星 · 超过95%的资源 192 浏览量
2022-07-09
05:59:51
上传
评论 1
收藏 71KB PDF 举报 
实验一
>> close all;
clear all;
dt = 0.001;
fm = 1;
fc = 10;
T = 5;
t = 0: dt : T;
mt = sqrt(2) * cos(2 * pi * fm * t);
%N0 = 0.01
%AM modulation
A = 2;
s_am = (A + mt).* cos(2 * pi * fc * t);
B = 2 * fm;
%noise = noise_nb(fc, B, N0, t);
%s_am = s_am + noise;
figure(1);
subplot(311);
plot(t, s_am); hold on;
plot(t, A + mt, 'r--');
title('AM 调制信号及其包络');
xlabel('t');
%AM demodulation
rt = s_am.* cos(2 * pi * fc * t);
rt = rt - mean(rt);
%[f, rf] = T2F(t, rt);
dt = t(2) - t(1);
T = t(end);
df = 1/T;
N = length(rt);
f = -N/2 * df: df: N/2 * df -df;
rf = fft(rt);
rf = T/N * fftshift(rf);
% END of T2F
% ==== [t, rt] = lpf(f, rf, B);
df = f(2) - f(1);
T = 1/df;
hf = zeros(1, length(f));
bf = [-floor(B / df): floor(B / df)] + floor(length(f) / 2);
hf(bf) = 1;
yf = hf.* rf;
% ==== [t, st] = F2T(f, yf);
df = f(2) - f(1);
Fmx = (f(end) - f(1) + df);
dt = 1 / Fmx;
N = length(yf);
T = dt * N;
% ==== t = -T / 2: dt: T/2 -dt;
t = 0: dt: T - dt;
sff = ifftshift(yf);
st = Fmx * ifft(sff);
% ==== END of F2T
rt = real(st);
% ==== END of lpf
subplot(312);
plot(t, rt); hold on;
plot(t, mt/2, 'r--');
title('相干解调后的信号波形与输入信号的比较');
xlabel('t');
subplot(313);
%[t, sf] = T2F(t, s_am);
dt = t(2) - t(1);
T = t(end);
df = 1/T;
N = length(s_am);
f = -N/2 * df:df: N/2 * df -df;
sf = fft(s_am);
sf = T/N * fftshift(sf);
% END of T2F
psf = (abs(sf).^2) / T;
plot(f, psf);
axis([-2 * fc 2 * fc 0 max(psf)]);
title('AM 信号功率谱');
xlabel('f');
>>
资源评论
科加斯5852023-06-10终于找到了超赞的宝藏资源，果断冲冲冲，支持！
