%用公式法實現(xiàn)圓陣指向性圖的繪制
close all
 clear all;
 N=60;
 c=1500;
 f=1500;
 alpha=2*pi/N;
 lamda=c/f;
r=lamda/0.4;
 x=0:pi/180:pi;
 theter=[0 pi/6];
 for j=1:2
     a=0;b=0;
 for i=1:60
    derta=r/c*[cos(x-(i-1)*alpha)-cos(theter(j)-(i-1)*alpha)];
     a=a+cos(2*pi*f.*derta);
     b=b+sin(2*pi*f.*derta);
 end
R=sqrt(a.^2+b.^2)/N;
 if j==1
     subplot(211);plot(x,abs(R));title('圓陣的指向性：無相移');xlabel('信號入射方向'),ylabel('指向性函數(shù)值');
 else 
subplot(212);plot(x,abs(R));title('圓陣的指向性：有相移');xlabel('信號入射方向'),ylabel('指向性函數(shù)值');
end
end