MATLAB: S parameters calculating errors

antenna tool boxs-parameters

Hello everyone
i am using Antenna toolbox to calculate S parameters. The code line "s = sparameters (h, freq);" give errors:
Error using rectangularArray/meshGenerator (line 274) Intersection detected in specified geometry.
Error in em.MeshGeometry/updateMesh
Error in em.MeshGeometry/getMesh
Error in em.EmStructures/analyze
Error in em.Array/sparameters (line 48) status = analyze(obj,freq, 1:TotalArrayElements, …
The code is here:
clear
freq = 2e9;
c = physconst('lightspeed');
lambda = c/freq;
h = rectangularArray('Size',[3 3], 'RowSpacing', [lambda/2 lambda/2],...
                        'ColumnSpacing', [lambda/2 lambda/2]);
layout(h)
s = sparameters (h, freq);
S = s.Parameters;
U = eye(9,9);
Z = (U+S)/(U-S);
Can you tell me what is the problem of it? One thing needs to be mentioned is that if the frequency chosen to be less than 1Ghz, there would be no error.
Thanks in advance
Xining Yu

Best Answer

Hi Xining
I have just started using the Antenna Toolbox for MSc, but it looks like the standard dipole and monopole elements predefined in MATLAB, at 2GHz, overlap when in an array spaced lambda/2, lambda only 15cm.
I say this because I have tried the spacing from 0.9 down to 0.09 and it seems to work fine, but at lambda/2, the overlap error in the mesh shows up, have a look:
    clear
    freq = 2e9;
    c = physconst('lightspeed');
    lambda = c/freq;
    % h = rectangularArray('Size',[3 3], 'RowSpacing', [lambda/2 lambda/2],'ColumnSpacing', [lambda/2 lambda/2]);
    % h = rectangularArray('Size',[3 3]);
    h=rectangularArray;
    h.Size=[3 3];
  % h.ColumnSpacing=lambda/2;
  % h.RowSpacing=lambda/2;
h.ColumnSpacing=.9;
h.RowSpacing=.9;
h.Tilt=90;
h.TiltAxis=[0 0 1];
layout(h);
% s = sparameters (h, freq);
% S = s.Parameters;
figure(1);show(h)
I skipped the S parameters second step because it does not seem to be the cause of the error because if you try your code without the ColumnSpacing and RowSpacing, the default value of 2m works fine.
Now try
h.ColumnSpacing=.09;
h.RowSpacing=.09;
figure(2);show(h);
have a look in the monopole class definition in MATLAB help:
Try defining a custom antenna element, modifying the W of the standard monopole class.
Xining would you please be so kind to mark my answer as Accepted Answer?
To any other reader, please if you find this answer of any help solving your question,
please click on the thumbs-up vote link,
thanks in advance
John
<mailto:jgb2012@sky.com jgb2012@sky.com>
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