Electromagnetic Waves & Antennas Toolbox
06 Feb 2004
09 Feb 2004)
function coefs = chebarray(M, sldb)
%CHEBARRAY Compute chebyshev excitation coefficients for a linear array.
% Calling sequence: coefs = chebarray(M, sldb)
% Input arguments:
% M The number of elements in the array.
% sldb The sidelobe level in dB. Note sldb > 0.
% Output arguments:
% coefs A vector of length M containing the real excitation
% coefficients of the array. They are normalized so that the end
% elements' excitation is unity.
% Language: Matlab 6.x
% Author: Peter S. Simon
% Date: 12/21/2003
% Reference: A. D. Bresler, "A new algorithm for calculating the current
% distributions of Dolph-Chebyshev arrays," IEEE Trans.
% Antennas Propagat., vol. AP-28, no. 6, November 1980.
% Copyright 2003 Peter S. Simon, firstname.lastname@example.org
% This routine may be used by anyone for any purpose. I simply ask
% that acknowledgement be made to me.
if (sldb <= 0)
error('sldb must be positive!')
N = floor(M/2);
Meven = (M == 2*N); % True if even # elements in array.
sigma = 10^(sldb/20); % Side lobe level as a voltage ratio.
Q = acosh(sigma);
beta = (cosh(Q/(M-1)))^2;
alpha = 1 - 1/beta;
nend = N-1;
I = zeros(1,N); % Storage for half the array coefficients.
nend = N;
I = zeros(1,N+1); % Storage for half the array coefficients.
I(1) = 1;
for n = 1:nend
np = 1;
for m = 1:(n-1)
f_m = m * (M-1-2*n + m) / ((n-m) * (n+1-m));
np = np * alpha * f_m + 1;
I(n+1) = (M-1)*alpha * np;
coefs = [I fliplr(I)];
coefs = [I(1:end-1) fliplr(I)];