clear,
fi=-pi/2:.01:pi/2;
eo=cos(pi/2*cos(pi/2-fi))./sin(pi/2-fi);
eo=1;
for i=1:100
    dl=i/50;
    et=(1+exp(-j*(2*pi*2*dl*cos(fi)+pi))).*eo;
    et(1)=2;et(315)=2;
    polar(fi,abs(et).^2);
    set(findobj('Type','line'),'LineWidth',1.5)
    pause(.01)
end
