mie2_ab.m

MieMatlabMaetzler.zip 非常全功能的Mie散射程序 matlab

function result = Mie2_ab(eps1,mu1,x)

% Computes a matrix of Mie Coefficients, an, bn, of order
% n=1 to nmax, for given complex permittivity and permeability
% ratios eps1=eps1'+ieps1", mu1=mu1'+imu1" between inside and outside 
% of the sphereand size parameter x=k0*a 
% where k0= wave number in ambient medium for spheres of radius a;
% Eq. (4.88) of Bohren and Huffman (1983), BEWI:TDD122
% C. M鋞zler, July 2002

m=sqrt(eps1.*mu1);            % refractive index ratio
z=m.*x;
z1=sqrt(mu1./eps1);           % impedance ratio
nmax=round(2+x+4*x.^(1/3));
nmx=round(max(nmax,abs(z))+16);
n=(1:nmax); nu = (n+0.5); 
sx=sqrt(0.5*pi*x);
px=sx.*besselj(nu,x);
p1x=[sin(x), px(1:nmax-1)];
chx=-sx.*bessely(nu,x);
ch1x=[cos(x), chx(1:nmax-1)];
gsx=px-i*chx; gs1x=p1x-i*ch1x;
dnx(nmx)=0+0i;
for j=nmx:-1:2      % Computation of Dn(z) according to (4.89) of B+H (1983)
    dnx(j-1)=j./z-1/(dnx(j)+j./z);
end;
dn=dnx(n);
da=dn.*z1+n./x; 
db=dn./z1+n./x;

an=(da.*px-p1x)./(da.*gsx-gs1x);
bn=(db.*px-p1x)./(db.*gsx-gs1x);

result=[an; bn];