bessel -constantwidthbf_music.m

实现任意结构阵列的恒定束宽波束形成法

clear all;close all;clc;

M=15;
N=1000;n=1:N;
J=33;
f=linspace(10e3,14e3,J);f0=10e3;fc=12e3;
c=3.e8;d=0.5*c/fc;
DOA=[9 12];SNR=6;

ang=linspace(0,180,500);
r1=[90 97.7 105.5];
a=exp(j*2*pi*d*f0*(0:M-1).'*cos(ang/180*pi)/c);
b=chebwin(M,25);b=diag(b.');
w0=b*exp(j*2*pi*d*f0*(0:M-1).'*cos(r1/180*pi)/c);
P=abs(w0'*a);maxP=max(max(P));
figure(1)
plot(ang,20*log10(P/maxP),'k');
ne=51;Tf=zeros(M,2*ne+1);T0=zeros(M,2*ne+1);
for n=-ne:ne
    for m=1:M
        z=2*pi*(m-1)*d*f0/c;
        T0(m,n+ne+1)=besselj(n,z)*j^n*exp(j*n*pi/4);
    end
end
for p=1:J    
    for n=-ne:ne
        for m=1:M
            z=2*pi*(m-1)*d*f(p)/c;
            Tf(m,n+ne+1)=besselj(n,z)*j^n*exp(j*n*pi/4);
        end
    end
    T=Tf*inv(Tf'*Tf)*T0';
    wf=T*w0;
    a=exp(j*2*pi*(0:M-1).'*d*f(p)/c*cos(ang/180*pi));
    Ff=abs(wf'*a);maxF=max(max(Ff));
    figure(2)
    plot(ang,20*log10(Ff/maxF),'k');hold on;
end
break;


y=w'*X;
R=y*y'/N;           %computer coherent covariance in frequency domain 
[U1 D1]=eig(R);
En=U1(:,1);            %noise subspac  
b=(w'*a)'*En;
Pmusic=1./(sum(abs(b).^2,2));
figure(2)
plot(ang,10*log10(Pmusic));grid on;xlim([20 50]);