武汉理工大学——通信原理实验报告调试图以及实验代码

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 modulationA = 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 demodulationrt = 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 F2Trt = real(st);% ==== END of lpfsubplot(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 T2Fpsf = (abs(sf).^2) / T;plot(f, psf);axis([-2 * fc 2 * fc 0 max(psf)]);title('AM 信号功率谱');xlabel('f');>>实验二>> clear all;close all;A = 1;fc = 2; %2HzN_sample = 8;N = 500; %码元数Ts = 1; %1 Baud/sdt = Ts/fc/N_sample; %波形采样间隔t = 0: dt: N * Ts - dt;Lt = length(t);%产生二进制信源d = sign(randn(1, N));%dd = sigexpand((d + 1)/2, fc * N_sample);N = length((d + 1)/2);out = zeros(fc * N_sample, N);out(1, :) = d;dd = reshape(out, 1, fc * N_sample * N);%END of sigexpandgt = ones(1, fc * N_sample); %NRZ波形%gt = ones(1, fc * N_sample * N);figure(1);subplot(221); %输入NRZ信号波形（单极性）d_NRZ = conv(dd, gt);gt = ones(1, length(d_NRZ));d_NRZ = d_NRZ + gt;d_NRZ = 0.5 * d_NRZ;plot(t, d_NRZ(1 : length(t)));axis([0 10 0 1.2]);ylabel('输入信号');subplot(222); %输入NRZ频谱%[f, d_NRZf] = T2F(t, d_NRZ(1 : length(t)));dt = t(2) - t(1);T = t(end);df = 1/T;N = length(d_NRZ);f = -N/2 * df: df: N/2 * df -df;d_NRZf = fft(d_NRZ); d_NRZf = T/N * fftshift(d_NRZf);%END of T2Fplot(f, 10 * log10(abs(d_NRZf).^2/T)); axis([-2 2 -50 10]);ylabel('输入信号功率谱密度（dB/Hz）');%OOK信号ht = A * cos(2 * pi * fc * t);s_2ask = d_NRZ(1 : Lt) .* ht;subplot(223);plot(t, s_2ask);axis([0 10 -1.2 1.2]);ylabel('ASK');%[f, s_2askf] = T2F(t, s_2ask);dt = t(2) - t(1);T = t(end);df = 1/T;N = length(s_2ask);f = -N/2 * df: df: N/2 * df -df;s_2askf = fft(s_2ask);s_2askf = T/N * fftshift(s_2askf);%END of T2Fsubplot(224);plot(f, 10 * log10(abs(s_2askf).^2/T)); axis([-6 6 -50 10]);ylabel('ASK功率谱密度（dB/Hz）');figure(2);%2PSK信号d_2psk = 2 * d_NRZ - 1;s_2psk = d_2psk(1 : Lt) .* ht;subplot(221);plot(t, s_2psk);axis([0 10 -1.2 1.2]);ylabel('2PSK');subplot(222);%[f, s_2pskf] = T2F(t, s_2psk);dt = t(2) - t(1);T = t(end);df = 1/T;N = length(s_2psk);f = -N/2 * df: df: N/2 * df -df;s_2pskf = fft(s_2psk);s_2pskf = T/N * fftshift(s_2pskf);%END of T2Fplot(f, 10 * log10(abs(s_2pskf).^2/T));axis([-6 6 -50 10]);ylabel('2PSK功率谱密度(dB/Hz)');%2FSK信号sd_2fsk = 2 * d_NRZ - 1;s_2fsk = A * cos(2 * pi * fc * t + 2 * pi * sd_2fsk(1 : length(t)) .* t);subplot(223);plot(t, s_2fsk);axis([1 10 -1.2 1.2]);xlabel('t');ylabel('2FSK');subplot(224);%[f, s_2fskf] = T2F(t, s_2fsk);dt = t(2) - t(1);T = t(end);df = 1/T;N = length(s_2fsk);f = -N/2 * df: df: N/2 * df -df;s_2fskf = fft(s_2fsk);s_2fskf = T/N * fftshift(s_2fskf);%END of T2Fplot(f, 10 * log10(abs(s_2fskf).^2/T));axis([-6 6 -50 10]);xlabel('f');ylabel('2FSK功率谱密度（dB/Hz）');>>。