test_script.m

% GNU General Public License v3.0 | Copyright (c) 2022 Alexandros Pitilakis

clear all; close all; clc;

% This script produces a test configuration for the metasruface (e.g. a
% grating, and a circular aperture) and calculates & plots the scattering
% pattern for an obliquely-incident plane wave illumination.
%
% This particular grating implements an (approximately) retro-reflecting
% metasurface, when illuminated from theta=30 deg (oblique incidence). You
% can compare this pattern against the the specular reflection pattern,
% by setting pp=0*pp (i.e., like a flat metallic reflector plate).

% ----------- Test Configuration for Metasurface ------------

% Define a phase-grating on the metasurface
N=40;
[nn,mm] = meshgrid( 1:N,1:N );
pp = zeros(size(nn));
per = 10;
pp( mod(nn,per)<=((per-1)/2) ) = pi; % pp == phase_profile

% Define a circular aperture (absorbing cells at the four corners)
ap = ones(size(pp));
dd = sqrt( (nn-N/2).^2 + (mm-N/2).^2 );
ap( dd > N/2 ) = 0; % ap = amplitude_profile

% ----------- Function Inputs ------------
freq = 1e12; % [Hz] Operating frequncy
wl = 3e8 / freq;

MetaSurf.duc = wl/10; % [m] cell-width (square)
MetaSurf.NumCellsXY = [ N N ]; % [.] number of cells in each dimension
MetaSurf.Refl_Ampli = ap; % [rad]
MetaSurf.Refl_Phase = pp; % [.]
MetaSurf.Cell_ScatPat_Exp = 1; % [.] cell-scat-pat is cos(theta)^n

Illumin.Type = 1; % Illumination/source type: 1=Plane, else=Spherical
Illumin.DOA = [ 30 , 0 ]; % [deg] theta+phi angles (for Type==1)
Illumin.xyz = [ 0 , 0 , 3e8/freq*5 ]; % [m] sphere center (for Type~=1)

Method.SPAR = 3; % [deg] % SPAR: Scattering-Pattern Angle-Resolution
Method.angspan = 0; % [deg] if set to zero, we scan entire hemisphere
Method.focusDir = [0,0]; % [deg](theta,phi) to "focus" calc on

% ----------- Call function to calc. scat-patt -----------
[E, theta, phi] = calc_ScatPat( freq , MetaSurf , Illumin , Method );
Unorm = abs(E).^2/max(abs(E(:)).^2);

% ----------- Plot scat-patt ----------- 
try
    figure;
    plot_3D_Pattern( theta*180/pi, phi*180/pi, Unorm , [3 6] )
    colormap jet  
catch
    error( ' Get "plot_3D_Pattern" from GitHub to plot the pattern!' )
end