Mutual coupling in antenna array

Hi all,

I'm trying to get the voltage distribution of the entire antenna array under specific excitation pattern when mutual coupling is taken into account.

However, I'm not sure about the results I've got from my program, below are the steps and results:

(1)Array geometry and working condition

1 transmit (top-left corner) and 3 receive elements arranged rectangular, spacing 0.5 * lambda in x/y direction;

terminated by 50ohm resisters(Default);

backed by infinitive ground;

only the transmit element is excited at 1V;

c = physconst('lightspeed');
fc = 24e9;
lambda = c/fc;

dx = 0.5 * lambda;
dy = 0.5 * lambda;
dz = 0.25 * lambda;
len = 0.495 * lambda;
width = cylinder2strip(lambda / 160);
Voltage_map = [1 0 0 0];

mydipole = dipole;
mydipole.Length = len;
mydipole.Width = width;
mydipole.Tilt = [90 90];
mydipole.TiltAxis = [0 1 0; 0 0 1];

myelement = reflector;
myelement.Exciter = mydipole;
myelement.GroundPlaneLength = inf;
myelement.Spacing = dz;

myarray = rectangularArray;
myarray.Element = myelement;
myarray.RowSpacing = dy;
myarray.ColumnSpacing = dx;
myarray.AmplitudeTaper = Voltage_map;

show(myarray);

(2)Voltage distribution derivation

Vo = Sparameters * Vin;

S = sparameters(myarray, fc);
Voltage = S.Parameters * Voltage_map';

(3)results

0.467586377317679 + 0.187044014975194i
0.201363968041588 - 0.122844419394166i
-0.0685242315036429 - 0.106783300795153i
-0.0190084411346258 + 0.0534820400032710i

However, the reults seems weird...and I'm not sure about the process is right or not.

Answer 1

[Chandra Amma Palanisamy]

Your results are consistent with the presence of mutual coupling. When the first port is excited, quantities such as ​, and describe the coupling from the first port to the other ports.

However, S-parameters are wave quantities rather than a voltage-transfer matrix. Hence, multiplying the S-parameter matrix by the excitation vector does not, in general, directly provide the physical terminal voltages.