field=sza_apfield(r,diameter) Design aperture field of SZA feeds - truncated Gaussian
0001 function field=sza_apfield(r,diameter) 0002 % field=sza_apfield(r,diameter) 0003 % 0004 % Design aperture field of SZA feeds - truncated Gaussian 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=-11.6; 0017 0018 % Corresponding Gauss prob rel to peak of 1 0019 p=10^(dB/10); 0020 0021 % Electric field is sqrt of power 0022 p=sqrt(p); 0023 0024 % Find x val for this on Gauss curve with sigma=1 0025 % Probably a better way to do this... 0026 x=0:0.01:10; 0027 y=gauss([1,0,1],x); 0028 x=interp1(y,x,p,'cubic'); 0029 0030 % Sigma to p at dia 0031 s=(diameter(1)/2)/x; 0032 0033 % Calc app field values 0034 field=gauss([1,0,s],r); 0035 0036 % Zero beyond dish edge 0037 field(r>diameter(1)/2)=0; 0038 0039 % Zero where shadowed by secondary 0040 % turn this off - due to coarse resolution in beam calc shadowed area 0041 % is bigger than proper... 0042 field(r<diameter(2)/2)=0; 0043 0044 return