How do I simulate a ground antenna with a V shaped reflector?

I managed to build a ground antenna but I am not able to build a V shpaped reflector around it. This is what the code looks like for now:

tx = design(monopoleRadial, fc);

%% Adjust Rod Lengths and Radial Angles

% 1. Set the vertical monopole rod length (in meters)

tx.Height = 0.58;

% 2. Set the length of each ground radial rod (in meters)

tx.RadialLength = 0.58;

% 3. Set the angle between the radials and the horizontal plane (in degrees)

tx.RadialTilt = 45;

% 4. Set the total number of ground radials

tx.NumRadials = 4;

% Designing a reflector

rc = reflectorCorner;

rc.Exciter = tx;

rc.Spacing = 0.15;

rc.CornerAngle = 90;

rc.GroundPlaneLength = 0.86;

rc.GroundPlaneWidth = 1.05;

rc.rotate([1 0 0], 90);

figure;

show(rc)

pattern(rc, fc)

I know I have to shift it as well but the error that is showing is for rc.rotate([1 0 0], 90) and I tried to get help of the Copilot but it did not help.

Answer 1

[Cris LaPierre]

I am not an antenna expert, but was intrigued because you said Copilot did not help. I therefore tried to understand the issue with my own prompting.

Note that we do not have your design requirements, so this response is exploratory at best.

The main issue I found is that reflectorCorner does not have a rotate method, so rc.rotate([1 0 0],90) is invalid. You probably need to use a supported property like Tilt and TiltAxis.

For testing, I used fc = 122 MHz. My goal was to get a working reflector rather than preserving all the original design parameters. The main implication is that, for your given antenna geometry, a strict 90 degree V reflector was problematic.

Working Frequency

The value below is the validated starting frequency for the stated monopole dimensions.

fc = 122e6;
fcMHz = fc/1e6

fcMHz = 122

Build the Working Reflector

This section uses the construction order that solved correctly in MATLAB.

rc = reflectorCorner;
rc.Exciter = monopoleRadial;
rc = design(rc,fc);
rc.Exciter.Height = 0.58;
rc.Exciter.RadialLength = 0.58;
rc.Exciter.RadialTilt = 45;
rc.Exciter.NumRadials = 4;
rc.Spacing = 0.58;
rc.CornerAngle = 140;
rc.GroundPlaneLength = 0.86;
rc.GroundPlaneWidth = 1.05;
rc.TiltAxis = [1 0 0];
rc.Tilt = 90;
show(rc)

Resulting Reflector Geometry

The reflector panel size is left at the value generated by design because smaller manual panel sizes caused mesh intersection errors.

reflectorDesign = struct;
reflectorDesign.Spacing_m = rc.Spacing;
reflectorDesign.CornerAngle_deg = rc.CornerAngle;
reflectorDesign.GroundPlaneLength_m = rc.GroundPlaneLength;
reflectorDesign.GroundPlaneWidth_m = rc.GroundPlaneWidth;
reflectorDesign

reflectorDesign = struct with fields:
              Spacing_m: 0.5800
        CornerAngle_deg: 140
    GroundPlaneLength_m: 0.8600
     GroundPlaneWidth_m: 1.0500

Radiation Pattern

The updated reflector geometry solves and the pattern can be evaluated at fc.

pattern(rc,fc)

Warning: Graphics acceleration hardware is unavailable. Graphics quality and performance might be diminished. See MATLAB System Requirements.

Changes from your original script

• Replaced the invalid rotate call with the supported Tilt and TiltAxis properties
• Set fc = 122e6 Hz as the working frequency for the monopole geometry with Height = 0.58 m, RadialLength = 0.58 m, RadialTilt = 45 deg, and NumRadials = 4
• Built the reflector by assigning rc.Exciter = monopoleRadial first and then calling rc = design(rc,fc)
• Reapplied the custom monopole dimensions after design because the reflector design step resized the exciter
• Increased Spacing to 0.58 m because smaller tested values produced reflector intersection errors
• Kept the original reflector panel dimensions of GroundPlaneLength = 0.86 m and GroundPlaneWidth = 1.05 m because those values do work once the spacing and corner angle are corrected
• Used CornerAngle = 140 deg because a tighter 90 deg V-shape still intersected for this monopole radial geometry

If a strict 90 deg V-reflector is still required, the built-in reflectorCorner object is not enough for this monopole radial geometry and a custom reflector geometry will be needed.

If the monopole dimensions change, rerun an S-parameter or impedance sweep and update fc before redesigning the reflector.

[Cris LaPierre]

So the biggest change is with the position of the V reflector. In the original code, it was too close to the monopole/radials and collided with the antenna geometry, leading to the 'Intersection detected in specified geometry.' error.

I had to move the reflector placement to fix this error when running pattern(rc,fc)