fig4_27.m

《最优阵列处理》一书第四章的MATLAB例程

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%
%%%% Fig 4.27
%%%% Pattern sampling on psi space, using ifft to get weight
%%%% and get the reconstructed beampattern using fft 
%%%% Xiaomin Lu  11-2-98	
%%%% Updated by K. Bell 9/29/00	
%%%% Updated by Lillian Xiaolan Xu 02/12/2001, K. Bell 7/23/01, 9/30/01
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*****************************%


clear all
close all

N = 11;
[ux,uy] = meshgrid(-1:1/30:1);

for k1 = 0:N-1
   for k2 = 0:N-1
      r = sqrt( (k1-(N-1)/2)^2+(k2-(N-1)/2)^2 );
      if( r < sqrt(5) )  Bpsi(k1+1,k2+1) = 1; end
      if( r == sqrt(5) )  Bpsi(k1+1,k2+1) = 1/2; end
      if( r > sqrt(5) )  Bpsi(k1+1,k2+1) = 0; end
   end
end

for k1 = 0:N-1
   for k2 = 0:N-1
     t1 = k1-(N-1)/2;
     t2 = k2-(N-1)/2;
   B(k1+1,k2+1) = exp(-j*(N-1)/2*(t1*2*pi/N)-j*(N-1)/2*(t2*2*pi/N))*Bpsi(k1+1,k2+1)';
   end
end

w = ifft2(B);
w = real(w)-j*imag(w);

for n = 0:N-1
   for m = 0:N-1
     w(n+1,m+1) = w(n+1,m+1)*exp(j*pi/N*(N-1)*(n+m));
    end
end 


Beam = 0;
for n = 0:N-1
  for m = 0:N-1
      Beam = Beam + w(n+1,m+1)*exp(j*n*pi*ux+j*m*pi*uy);
  end
end
Beam = Beam.*exp(-j*(N-1)/2*pi*ux-j*(N-1)/2*pi*uy);

Beam = 20*log10(abs(Beam));
for k1 = 1:size(Beam,1)
  for k2 = 1:size(Beam,2)
     if (Beam(k1,k2)<-80) Beam(k1,k2)=-80; end
  end
end


mesh(ux,uy,Beam)
axis([-1 1 -1 1 -80 0])
xlabel('\it u_x','Fontsize',14);
ylabel('\it u_y','Fontsize',14);
zlabel('Beam pattern (dB)','Fontsize',14);
%title('Regenerated Beampattern, using pattern sampling') 
figure

u = -1:1/100:1;
t = 1;
for phi = [0 30 60 90]
   ux = u*cos(phi/180*pi);
   uy = u*sin(phi/180*pi);
   
   Beam = 0;
   for n = 0:N-1
     for m = 0:N-1
      Beam = Beam + w(n+1,m+1)*exp(j*n*pi*ux+j*m*pi*uy);
     end
   end
   Beam = Beam.*exp(-j*(N-1)/2*pi*ux-j*(N-1)/2*pi*uy);
   table(t,:) = 20*log10(abs(Beam));
   
   t = t+1;
end
subplot(2,2,1)
plot(u,table(1,:))
grid
axis([-1 1 -60 10])
xlabel('\it u_r','Fontsize',14);
ylabel('Beam pattern (dB)','Fontsize',14);
text(-0.9,4,'\phi = 0^o','Fontsize',12)
%text(-1,18,'                        Pattern cuts at several phis')

subplot(2,2,2)
plot(u,table(2,:))
grid
axis([-1 1 -60 10])
xlabel('\it u_r','Fontsize',14);
ylabel('Beam pattern (dB)','Fontsize',14);
text(-0.9,4,'\phi = 30^o','Fontsize',12)

subplot(2,2,3)
plot(u,table(3,:))
grid
axis([-1 1 -60 10])
xlabel('\it u_r','Fontsize',14);
ylabel('Beam pattern (dB)','Fontsize',14);
text(-0.9,4,'\phi = 60^o','Fontsize',12)

subplot(2,2,4)
plot(u,table(4,:))
grid
axis([-1 1 -60 10])
xlabel('\it u_r','Fontsize',14);
ylabel('Beam pattern (dB)','Fontsize',14);
text(-0.9,4,'\phi = 90^o','Fontsize',12)