How to use antenna toolbox with a measured antenna ?

Hello !

I am trying to plot an antenna pattern from in situ real measurements of an antenna. My measurements comprise X, Y Z in m and the measured attenuation in dB.

After conversion into azimuth and elevation, unfortunately, this does not seem compatible with either measuredAntenna or patterncustom.

With patterncustom I get the following error :

Error filling holes for shared_channel:patternCustom:RepeatedPoints.

Floating point numbers are not allowed as holes. They should be

converted to character vectors.

With measured antenna, MagE I do not have, as I only have the measured attenuation...

Anyway to get my antenna plots (3D and sections) from my measurements ?

Thanks in advance,

Kindly,

[Ganapathi Subramanian R]

What do you mean by attentuation here and do you have any other data related to directivity?

[Félix]

Thank your for your help !

I do not have any directivity data, we cover a semi sphere around our measured antenna. At each sample point, we measure the signal intensity loss, in dB, which I refer to as attenuation.

Typically looks like this :

X(m) Y(m) Z(m) Attenuation(dB)

-2,488942666 6,88120177 21,05000067 -36.5

-2,06476295 7,036021853 21,19000068 -28.1

Thanks !

[Ganapathi Subramanian R]

Hi Felix,

According to recent MATLAB documentation, the 'patternCustom' function requires antenna directivity, E-fields, H-fields, or power of an antenna or array as input for 'magE' parameter . I suggest you to transform the attentuation data into directivity by finding a correlation between the observed attentuation and directivity.

For further information regarding 'patternCustom' function, please refer to the below documentation.

https://www.mathworks.com/help/antenna/ref/patterncustom.html

[Félix]

thannks, it is what i had gathered as well...

Answer 1

[Pooja Kumari]

Hi Felix,

I unserstand you are trying to plot an antenna pattern from in situ real measurements of an antenna. You are facing "Error filling holes for shared_channel:patternCustom:RepeatedPoints.Floating point numbers are not allowed as holes. They should be converted to character vectors." error using Pattern Custom function.

If you have attenuation in dB (Attenuation), you can convert it to a relative magnitude scale by assuming that the attenuation is relative to the maximum signal strength you measured or a known reference.

I think the error will be resolved when the parameters are passed in the correct order as follows:

patternCustom(magE, theta, phi);

For more information on Pattern Custom function, you can refer to the below documentation:

https://www.mathworks.com/help/antenna/ref/patterncustom.html

[Félix]

I have tried that as well, unsuccesfully. I will try to measure something else than attenuation, thanks for your help

Answer 2

[Shashank Kulkarni]

The problem: You have antenna measurements as X, Y, Z positions with signal attenuation, but both patternCustom and measuredAntenna expect angular data — not Cartesian coordinates.

Why you got errors:

- patternCustom expects theta and phi angles (spherical coordinates in degrees), not X/Y/Z positions. The "RepeatedPoints" error occurs when it can't interpret your inputs as a valid angular grid.

- measuredAntenna expects a Direction matrix with columns [azimuth, elevation, radius] in degrees/meters — again, not Cartesian X/Y/Z.

What you need to do:

1. Convert your X/Y/Z positions to angles. Compute the distance R from the origin to each point, then derive theta (angle from the vertical axis) and phi (angle in the horizontal plane) using inverse trig

functions.

2. Convert attenuation to a pattern quantity. Flip the sign (less attenuation = more gain), then normalize so the peak is 0 dB. This gives you a relative radiation pattern.

3. For patternCustom: Pass the converted pattern values, theta angles, and phi angles — all as vectors of the same length. Alternatively, interpolate onto a regular angular grid and pass as a matrix with

theta and phi vectors.

4. For measuredAntenna with txsite: Interpolate your data onto a regular azimuth/elevation grid. Set E = [] and populate Directivity. Note that txsite requires a specific internal data ordering — the

Direction matrix must use meshgrid-default ordering (no transpose), while the Directivity values must be transposed before flattening.

% === Your measured data ===
% x, y, z: measurement positions (meters)
% atten_dB: measured attenuation at each point (dB)

% Step 1: Convert Cartesian to spherical angles
R = sqrt(x.^2 + y.^2 + z.^2);
theta_meas = rad2deg(acos(z ./ R));    % theta: 0=zenith, 90=horizon
phi_meas = rad2deg(atan2(y, x));       % phi: angle in x-y plane

% Step 2: Convert attenuation to relative pattern
patternData_dB = -atten_dB;
patternData_dB = patternData_dB - max(patternData_dB);

% Step 3: Visualize with patternCustom (all vectors, same length)
figure;
patternCustom(patternData_dB, theta_meas, phi_meas);

% === To create measuredAntenna for txsite/rxsite ===
% Interpolate onto regular az/el grid
az = -180:5:180;  el = -90:5:90;
az_meas = rad2deg(atan2(y, x));
el_meas = rad2deg(asin(z ./ R));

[azGrid, elGrid] = meshgrid(az, el);
F = scatteredInterpolant(az_meas(:), el_meas(:), patternData_dB(:), "natural", "nearest");
patAzEl = F(azGrid, elGrid);  % Nel-by-Naz

% Direction: el-fast (NO transpose — required for txsite)
[phi_d, elv_d] = meshgrid(az, el);
numPoints = numel(phi_d);
R_far = max(R);
Direction = [phi_d(:) elv_d(:) R_far*ones(numPoints, 1)];

% Directivity: az-fast (transpose then flatten)
D = patAzEl';  D = D(:);

freq = 2.4e9;  % your measurement frequency
mAnt = measuredAntenna( ...
    E = [], ...
    Directivity = D, ...
    Direction = Direction, ...
    FieldFrequency = freq, ...
    Azimuth = az, ...
    Elevation = el);

% Use with txsite
tx = txsite(Antenna=mAnt, TransmitterFrequency=freq, ...
    TransmitterPower=10, AntennaHeight=30);
coverage(tx, SignalStrengths=[-60 -70 -80 -90], MaxRange=5000);