I'm using the Phased Array System Toolbox R2019b.
I'm trying to run a 16x16 element subarray inside a panel of varying size.
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If I make the panel 3 x 3 subarrays, I get a reported directivity of 40 dBi. This is the right answer.
fc = 8.5 GHz; lambda = 0.0353 m; element seperation = 0.6 lambda; length of one side of panel = 3*16*0.6*0.0353 = 1.0166 m
Area = 1.0335 m^2; Antenna Gain = 4*pi*A / lambda^2 = 4*pi*1.0335 / 0.0353^2 = 1.0422e+04 => 40.1795 dBi
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If I make the panel 16 x 16 subarrays, I get a reported directivity of 46 dBi.
Antenna Gain = 4*pi*29.3992 / 0.0353^2 = 2.9648e+05 => 54.7200 dBi is what I think it should be.
If I make the panel 20 x 20 subarrays, I still get a reported directivity of 46 dBi. Source code below.
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%% Control:
fc = 8.5e9; % Frequency of operation (Hz)
Az_Steer = 0; % Az beam steer (deg)
El_Steer = 0; % El beam steer (deg)
Panel_Subarray_Rows = 20; % Number of sub-arrays in row
Panel_Subarray_Cols = 20; % Number of sub-arrays in column
%% Constants & Derived:
c = physconst('LightSpeed'); % Lightspeed (m/s)
Steer_Vec = [Az_Steer; El_Steer]; % Steering Vector (deg)
Lambda = 3e8/fc; % Wavelength (m)
M = 16; % Sub-array number of elements on each row
N = 16; % Sub-array number of elements on each column
dy = 21.5e-3; % Sub-array spacing between elements on each row (m)
dz = 21.5e-3; % Sub-array spacing between elements on each column (m)
%% Element:
Element = phased.CosineAntennaElement('FrequencyRange',[7.75e9 8.5e9], 'CosinePower',1.0);
% Plot Element Pattern Az and El:
figure
subplot(2,1,1)
pattern(Element,fc,-90:0.5:90,0,'Type','powerdb','CoordinateSystem','polar')
title('Element Az Cut (El Angle = 0 deg)')
subplot(2,1,2)
pattern(Element,fc,0,-90:0.5:90,'Type','powerdb','CoordinateSystem','polar')
title('Element El Cut (Az Angle = 0 deg)')
%% Subarray:
% Create Subarray with Triangular Grid:
Subarray = phased.URA([N M],[dz dy],'Lattice','Triangular','Element',Element);
% View Subarray:
figure
viewArray(Subarray,'Title','BFIC Sub-Array with Triangular Grid');
% Steer Subarray:
Steer_Vec_Sub_Arry = phased.SteeringVector('SensorArray',Subarray,'PropagationSpeed',c);
w_sub = Steer_Vec_Sub_Arry(fc,Steer_Vec);
% Plot Steered Subarray - Az and El:
figure
subplot(2,1,1)
pattern(Subarray,fc,-90:0.5:90,0,'Type','directivity','CoordinateSystem','rectangular', ...
'PropagationSpeed',c,'Weights',w_sub);
title(['Subarray Az Cut (El Angle = 0 deg) For Beamsteer = ' num2str(Az_Steer) ' deg'])
subplot(2,1,2)
pattern(Subarray,fc,0,-90:0.5:90,'Type','directivity','CoordinateSystem','rectangular', ...
'PropagationSpeed',c,'Weights',w_sub);
title(['Subarray El Cut (Az Angle = 0 deg) For Beamsteer = ' num2str(El_Steer) ' deg'])
%% Array Panel:
Panel = phased.ReplicatedSubarray('Subarray',Subarray,...
'Layout','Rectangular',...
'GridSize',[Panel_Subarray_Rows Panel_Subarray_Cols], ...
'GridSpacing','Auto', ...
'SubarraySteering','Phase', ...
'PhaseShifterFrequency',fc);
% Steer Panel:
Steer_Vec_Panel = phased.SteeringVector('SensorArray',Panel,'PropagationSpeed',c);
wts_panel = Steer_Vec_Panel(fc,Steer_Vec);
figure
viewArray(Panel,'Title','Panel Using BFIC');
% Directivity:
figure
subplot(2,1,1)
pattern(Panel,fc,-90:0.5:90,0,'Type','directivity','CoordinateSystem','rectangular', ...
'PropagationSpeed',c,'Weights',wts_panel);
title(['Panel Az Cut (El Angle = 0 deg) For Beamsteer = ' num2str(Az_Steer) ' deg'])
subplot(2,1,2)
pattern(Panel,fc,0,-90:0.5:90,'Type','directivity','CoordinateSystem','rectangular', ...
'PropagationSpeed',c,'Weights',wts_panel);
title(['Panel El Cut (Az Angle = 0 deg) For Beamsteer = ' num2str(El_Steer) ' deg'])
