field=apfield_sza(r,diameter) SZA feeds will have Gaussian taper
0001 function field=apfield_sza(r,diameter) 0002 % field=apfield_sza(r,diameter) 0003 % 0004 % SZA feeds will have Gaussian taper 0005 0006 % Diameters default to actual sizes 0007 if(~exist('diameter')) 0008 diameter=3.5; 0009 end 0010 0011 if(length(diameter)==1) 0012 diameter(2)=0.35; 0013 end 0014 0015 % dB down in power at edge of dish 0016 %dB=-14; 0017 % 2008 we measured and calculated and decided that we have 12dB 0018 % taper, not 14 0019 dB=-11.6; 0020 0021 % Corresponding Gauss prob rel to peak of 1 0022 p=10^(dB/10); 0023 0024 % Electric field is sqrt of power 0025 p=sqrt(p); 0026 0027 % Find x val for this on Gauss curve with sigma=1 0028 % Probably a better way to do this... 0029 x=0:0.01:10; 0030 y=gauss([1,0,1],x); 0031 x=interp1(y,x,p,'cubic'); 0032 0033 % Sigma to p at dia 0034 s=(diameter(1)/2)/x; 0035 0036 % Calc app field values 0037 field=gauss([1,0,s],r); 0038 0039 % Zero beyond dish edge 0040 field(r>diameter(1)/2)=0; 0041 0042 % Zero where shadowed by secondary 0043 % turn this off - due to coarse resolution in beam calc shadowed area 0044 % is bigger than proper... 0045 field(r<diameter(2)/2)=0; 0046 0047 return