2FSK 信号的调制解调与频谱绘制的 matlab 仿真
a=randint(1,16);
t=0.0001:0.001:1;
inisig=a(ceil(t./(1/15)));
subplot(5,1,1)
plot(t,inisig)
axis([0,1,-1.5,1.5])
title('原信号');
%调制
f1=200;
f2=100;
carrier1=cos(2*pi*f1*t);
carrier2=cos(2*pi*f2*t);
modulation_wave=zeros(1,length(t));
for i=1:length(t)
if(inisig(i)==0)
modulation_wave(i)=carrier1(i);
else
modulation_wave(i)=carrier2(i);
end
end
subplot(5,1,2)
plot(t,modulation_wave)
axis([0,1,-1.5,1.5])
title('调制信号');
%2fsk 信号加噪
noise_wave=awgn(modulation_wave,100);
%设计带通滤波器
[num1 den1]=butter(10,[2*0.9*f1*pi,2*1.1*f1*pi],'s');
[num2 den2]=butter(10,[2*0.9*f2*pi,2*1.1*f2*pi],'s');
daiout1_h=tf(num1,den1);
daiout2_h=tf(num2,den2);