%SMI方向图和性能
clear all
close all
clc
j=sqrt(-1);
% 天线参数的设定%
N=16; %阵元数
d_lamda=0.5; %阵元间距与波长的比值
M=500; %采样点数
fs1=[1000 400 350]; %input('analong frequency is:');
fs2=[25000 26000 24000]; %input('carrying frequency is:');
mod=[0.4 0.4 0.6]; %Ka 调幅指数
snr=[0 40,50 ]; %[期望信号 干扰信号1 干扰信号2]的信噪比
doa=[20 40 60]; %[期望信号 干扰信号1 干扰信号2]的方位角
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
m=0:M-1;
n=0:N-1;
amp=10.^(snr/20); %最大幅度值
%形成信号矩阵和方向矢量矩阵。
for k=1:size(amp',1)
st(k,:)=amp(k)*(1+mod(k)*sin(2*pi*fs1(k)/100000*m)).*exp(j*2*pi*fs2(k)/100000*m); %AM调幅波
d(:,k)=exp(j*2*pi*d_lamda*n'*sin(doa(k)*pi/180)); %直线阵
end
for i=1:N
noise(i,:)=randn(1,M);
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%输出采样协方差矩阵
X=d*st+noise+j*noise; %输出信号
R=1/M*X*X';
%%形成SMI加权矢量。
Wopt=inv(R)*d(:,1); %d(:,1)表示期望信号方向矢量。
%用于搜索
R=0;
for angle1=-90:90
R=R+1;
d1(:,R)=exp(j*2*n'*pi*d_lamda*sin(angle1*pi/180));
end
%得到方向图,方向矢量中包含有期望信号和干扰信号。
p(1,:)=Wopt'*d1;
p=abs(p);
pmax=max(p);
p0=p/pmax; %规一化
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
angle1=-90:90;
p0dB=20*log10(p0);
plot(angle1,p0dB,'-r');
title('p of SMI');
xlabel('Arrival Angle');
ylabel('Array Response dB');
grid on
figure;
subplot(3,1,1);
plot(m,st(1,:),'-m');
title('期望信号');
subplot(3,1,2);
plot(m,st(2,:),'.-.g');
title('干扰信号1');
subplot(3,1,3);
plot(m,st(3,:),'-*b');
title('干扰信号2');