MATLAB数字信号调制解调（ask,psk,fsk等）仿真

clear all close all i=10; j=5000; fc=4; fm=i/5; B=2*fm; t=linspace(0,5,j); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%产生基带信号 a=round(rand(1,i));%对10个随机数取整 st1=t;%将st1定义成了5000个数的序列 for n=1:10 if a(n)<1; for m=j/i*(n-1)+1:j/i*n%500个 st1(m)=0; end else for m=j/i*(n-1)+1:j/i*n st1(m)=1; end end end figure(1); subplot(311); plot(t,st1); title('二进制随机序列'); axis([0,5,-1,2]);%t范围0-5,st2范围-1到2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%差分变换 b=zeros(1,i); b(1)=a(1); for n=2:10 if a(n)>=1; if b(n-1)>=1 b(n)=0; else b(n)=1; end else b(n)=b(n-1); end end st1=t; for n=1:10 if b(n)<1; for m=j/i*(n-1)+1:j/i*n st1(m)=0; end else for m=j/i*(n-1)+1:j/i*n st1(m)=1; end end end subplot(312); plot(t,st1); title('相对码'); axis([0,5,-1,2]); st2=t; for k=1:j; if st1(k)>=1; st2(k)=0; else st2(k)=1; end end; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%载波信号 s1=sin(2*pi*fc*t); subplot(313); plot(s1); title('载波信号'); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%调制 d1=st1.*s1; d2=st2.*(-s1);%相移180 figure(2); subplot(421); plot(t,d1); title('st1*s1'); subplot(422); plot(t,d2); title('st2*s2'); e_dpsk=d1+d2; subplot(423); plot(t,e_dpsk); title('调制后波形'); noise=randn(1,j); dpsk=e_dpsk+noise;%加入噪声 subplot(424); plot(t,dpsk); title('加噪声信号'); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%相干解调 dpsk=dpsk.*sin(2*pi*fc*t);%与载波相乘 subplot(425); plot(t,dpsk); title('与载波相乘后波'); [f,af] = T2F(t,dpsk);%通过低通滤波器 [t,dpsk] = lpf(f,af,B); subplot(426); plot(t,dpsk); title('通过低通滤波器波形'); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%抽样判决 st=zeros(1,i); for m=0:i-1; if dpsk(1,m*500+250)<0; st(m+1)=0; for j=m*500+1:(m+1)*500; dpsk(1,j)=0; end else for j=m*500+1:(m+1)*500; st(m+1)=1; dpsk(1,j)=1; end end end subplot(427); plot(t,dpsk); axis([0,5,-1,2]); title('抽样判决后波形') %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%码反变换 dt=zeros(1,i); dt(1)=st(1); for n=2:10; if (st(n)-st(n-1))<=0&&(st(n)-st(n-1))>-1; dt(n)=0; else dt(n)=1; end end st=t; for n=1:10 if dt(n)<1; for m=j/i*(n-1)+1:j/i*n st(m)=0; end else for m=j/i*(n-1)+1:j/i*n st(m)=1; end end end subplot(428); plot(t,st); title('码反变换后波形'); axis([0,5,-1,2]);