function result = Rxx_laplacian(d_norm,phi_0_deg,sigma_deg,delta_phi_deg)
% result = Rxx_laplacian(d_norm,phi_0_deg,sigma_deg,delta_phi_deg)
%
% Computes the correlation of the real and imaginary parts of the
% signals in the case of a laplacian Power Azimuth Spectrum (PAS)
% at spacings given by d_norm. The PAS is characterised by the
% Angle Of Arrival (AOA) phi_0_deg and by its standard deviation
% sigma_deg.
%
%
% STANDARD DISCLAIMER
%
% CSys is furnishing this item "as is". CSys does not provide any
% warranty of the item whatsoever, whether express, implied, or
% statutory, including, but not limited to, any warranty of
% merchantability or fitness for a particular purpose or any
% warranty that the contents of the item will be error-free.
%
% In no respect shall CSys incur any liability for any damages,
% including, but limited to, direct, indirect, special, or
% consequential damages arising out of, resulting from, or any way
% connected to the use of the item, whether or not based upon
% warranty, contract, tort, or otherwise; whether or not injury was
% sustained by persons or property or otherwise; and whether or not
% loss was sustained from, or arose out of, the results of, the
% item, or any services that may be provided by CSys.
%
% (c) Laurent Schumacher, AAU-TKN/IES/KOM/CPK/CSys - July 2001

D             = 2*pi*d_norm;
% Conversion degree -> rad
phi_0_rad     = phi_0_deg*(pi/180);
sigma_rad     = sigma_deg*(pi/180);
delta_phi_rad = delta_phi_deg*(pi/180);

m                = 0;
result           = zeros(size(D));
tmp_xx_laplacian = ones(size(result));
while (m < 100)
    m = m +1;
    tmp_xx_laplacian = 4.*besselj(2*m,D).*cos(2*m*phi_0_rad) ...
	.*(sqrt(2)/sigma_rad+exp((-1)*sqrt(2)*delta_phi_rad/sigma_rad) ...
	   *(2*m*sin(2*m*delta_phi_rad) ...
             -sqrt(2)*cos(2*m*delta_phi_rad)/sigma_rad)) ...
	./(4*sqrt(2)*sigma_rad*m^2+sqrt(8)/sigma_rad);
    result = result + tmp_xx_laplacian;
end;