thin_wire.m

用矩量法计算细线天线的场分布

% pattern of a thin wire of lengh L
clear
rad=pi/180;
k=2*pi;
L=input('Enter wire length in wavelengths: ');
kl=k*L;
it=0;
for th=0:1:360
   thr=th*rad;
   it=it+1;
   E=0;
   if abs(sin(thr))>0.0001
      E=(cos(kl*cos(thr)/2)-cos(kl/2))/sin(thr); 
   end
   F(it)=abs(E);
   TR(it)=th*rad;
   T(it)=th;
   Fdb(it)=20*log10(abs(E)+1e-2);
end
figure(1),clf
subplot(121),polar(TR,F/max(F),'k-')
title('Polar Voltage Plot')
subplot(122),polardb(T,Fdb-max(Fdb),'k-')
% note: title location based on 40 dB dynamic range
text(-15,40*1.3,'Polar dB Plot')
 it=0;
 for th=0:3:180
	 jt=0; it=it+1;
   for ph=0:3:360
      jt=jt+1;
      thr=th*rad;
	   phr=ph*rad;
	   phd(it,jt)=ph;
	   thd(it,jt)=th; ct=cos(thr);
	   E=0;
      if abs(sin(thr))>0.0001
        E=(cos(kl*cos(thr)/2)-cos(kl/2))/sin(thr); 
      end
 	   u=sin(thr)*cos(phr);
	   v=sin(thr)*sin(phr);
	   w=cos(thr);
	   ff=abs(E);
	   f(it,jt)=ff;
	   X(it,jt)=f(it,jt)*u;
	   Y(it,jt)=f(it,jt)*v;
	   Z(it,jt)=f(it,jt)*w;
   end
end
MAX=max([max(max(X)),max(max(Y)),max(max(Z))]);
figure(2),clf
mesh(X/MAX,Y/MAX,Z/MAX)
axis([-1,1,-1,1,-1,1])
axis square
hold on
plot3([0 0],[0 0],[-1 1],'k-')
xlabel('X=|E|sin(t)cos(p)')
ylabel('Y=|E|sin(t)sin(p)')
zlabel('Z=|E|cos(t)');