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Sensor Array Analyzer, element gain and array factor not adding up as expected

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Sharath Ananth
Sharath Ananth on 30 Jul 2020 at 22:22
Edited: Sharath Ananth on 30 Jul 2020 at 22:23
I am using the sensor array analyzer to compute directvity. The attached screenshot shows a simple linear array with 10 elements and 1/2 lamda spacing.
The overall Array Directivity is shown as 16.14 dBi.
However the array factor of a simple 10x1 array is 10 dB.
Each individual antenna gain for a cosine(1,1) antenna is 7.7 dBi.
This would imply that the total gain should be 17.7 dBi and not 16.14 dBi. Can you explain what extra loss is being modelled to get us 16.14 dBi antenna gain instead of 17.7 dB
Code snippet to generate this:
%MATLAB Code from Sensor Array Analyzer App
%Generated by MATLAB 9.6 and Phased Array System Toolbox 4.1
%Generated on 30-Jul-2020 15:22:36
% Create a uniform linear array
h = phased.ULA;
h.NumElements = 10;
h.ElementSpacing = 0.2;
h.ArrayAxis = 'z';
%Create Cosine Antenna Element
el = phased.CosineAntennaElement;
el.CosinePower = [1 1];
h.Element = el;
%Assign frequencies and propagation speed
F = 750000000;
PS = 300000000;
%Create figure, panel, and axes
fig = figure;
panel = uipanel('Parent',fig);
hAxes = axes('Parent',panel,'Color','none');
NumCurves = length(F);
%Plot 2d graph
fmt = 'rectangular';
cutAngle = 0;
pattern(h, F, cutAngle, -90:90, 'PropagationSpeed', PS, 'Type', ...
'directivity', 'CoordinateSystem', fmt );
axis(hAxes,'square')
%Create legend
legend_string = cell(1,NumCurves);
lines = findobj(gca,'Type','line');
for idx = 1:NumCurves
[Fval, ~, Fletter] = engunits(F(idx));
legend_string{idx} = [num2str(Fval) Fletter 'Hz; No Steering'];
end
legend(legend_string, 'Location', 'southeast');

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