%用公式法實(shí)現(xiàn)圓陣指向性圖的繪制
close all
 clear all;
 N=28;M=60;
 c=1500;
 f=1500;
  fs=5000; 
  lamda=c/f;
r=lamda/0.4;
 jiajiao=2*pi/N;
nfft=256;
d=0.5;
n=1:nfft;
alpha=0.5;
derta2=0;
f0=5000;
A=2;
k=zeros(N,181);

for i=1:N
    z=[];
   for x=0:pi/180:pi
        s=x-(i-1)*jiajiao;
derta=2*pi*f0*alpha*(1+cos(2*s))./(c*cos(s))+derta2;
y=A*cos(2*pi*f0*n/fs)+A*alpha*cos(2*pi*f0*n/fs-derta);
p=sum(y.^2);
z=[z,p];
end
z=z/max(z);
k(i,:)=z;
end

R=[];
 for x=0:pi/180:pi;
a=0;b=0;
 for i=1:N
    der=r/c*[cos(x-(i-1)*jiajiao)-cos((i-1)*jiajiao)];
     a=a+k(i,:).*cos(2*pi*f.*der);
     b=b+k(i,:).*sin(2*pi*f.*der);
 end
 R=[R,sqrt(sum(a.^2)+sum(b.^2))/N];
end
R=R/max(R);
plot(x,abs(R));
 title('圓陣的指向性');xlabel('信號(hào)入射方向'),ylabel('指向性函數(shù)值');
 hold on;
 
N=60;
 c=1500;
 f=1500;
 alpha=2*pi/N;
 lamda=c/f;
r=lamda/0.4;
 x=0:pi/180:pi;
 theter=0 

 for i=1:60
    derta=r/c*[cos(x-(i-1)*alpha)-cos(theter-(i-1)*alpha)];
     a=a+cos(2*pi*f.*derta);
     b=b+sin(2*pi*f.*derta);
 end
c=sqrt(a.^2+b.^2)/N;






 
 x=0:pi/180:pi;
 plot(x,abs(R));
 title('圓陣的指向性');xlabel('信號(hào)入射方向'),ylabel('指向性函數(shù)值');
 hold on;
 plot(x,abs(c),'b');hold off;
 legend('加檔后','加檔前')