不用MATLAB里面的函数，自己写出来的2ASK的仿真程序，加入了白噪声，经过滤波后的波形有些变形，可能是滤波器的原因.zip

function [Pe]=ask2(snr_in_dB) %==================程序初始化及产生基带信号=================% N = 1000; fdc = 100; %码子个数N;抽样频率fdc=100 t = 0.01:0.01:N; source = randsrc(1,N,[0,1;0.5,0.5]); %产生0、1随机序列 A1 = ones(fdc,1); seq = A1 * source; A = seq(:)'; sy = sin(2*pi*3*t); %生成信号源 s =A .* sy; %被调信号s(t) %subplot(2,3,1); %plot(t,s); %hold on %=========================ASK信号的调制=====================% c = cos(300*t); %产生载波信号载波频率fc=300Hz x = s.*c; %ASK基带信号 %subplot(2,3,2); %plot(t,x); %hold on %==================ASK基带信号加入高斯白噪声=================% sigma = sqrt(10^(-snr_in_dB/10)/2); noise=sigma*randn(1,N*fdc); %subplot(2,3,3); %plot(t,noise); %hold on xnoise=x+noise; %有高斯白噪声的ASK信号 y=1/2*xnoise.*c; %相干解调 %subplot(2,3,4); %plot(t,y); %hold on %==============设计巴特沃思数字低通滤波器====================% wp=0.1*pi;ws=0.12*pi;Rp=1;Rs=15; [n,wn] = buttord(wp/pi,ws/pi,Rp,Rs); [b,a] = butter(n,wn); s1 = filter(b,a,y); %滤波 [H,w]=freqz(b,a,N,'whole'); f=(-N/2:1:N/2-1); %subplot(2,3,5); %plot(f,abs(fftshift(H))); %hold on S = 2*s1; %subplot(2,3,6); %plot(t,S); %=========================计算误码率==========================% %====================输入接收信号，并判决=====================% cntError = 0; %误码个数 Pe = 0; %误码率 temp = 1;errortemp = 0; e = 0; B = ones(1,N*fdc); T = B.*S; for i =1:N; T1 = T(temp:(i*fdc)); p = abs(T1); for I = temp:(i*fdc); if I <= 100; if p(I) > 0.1; e = e + 1; else e = e; end else if p(I-(i-1)*fdc) > 0.1; e = e + 1; else e = e; end end end if e < fdc/2 ; receive(i) = 0; else receive(i) = 1; end temp=i*fdc+1; e=0; end for j=1:N; if source(j) == receive(j); errortemp = 0; else errortemp = 1; end cntError = cntError + errortemp; end Pe=cntError/N;