Short vertical monopole antenna over lossy ground

I am measuring radio noise in the HF band (3-30 MHz) with a short vertical monopole antenna. I have three scenarios I would like to analyze for this measurement: 1) monopole over infinite ground plane, 2) monopole over radial system, and 3) monopole over lossy ground. The antenna toolbox can handle cases 1 and 2 but not 3. Has anyone written code that computes the pattern and impedance for a short vertical monopole over lossy ground?

Answer 1

[Abhishek Chakram]

Hi Robert Achatz,

Creating a complete and accurate code for computing the pattern and impedance of a short vertical monopole over lossy ground is a complex task. You would likely need to use numerical methods and have a deep understanding of electromagnetics to implement a full solution.

Here is a simplified outline of steps you might take in MATLAB to model this scenario:

1. Define the properties of the monopole and the lossy ground.
2. Use an appropriate numerical method, like the Method of Moments, to solve for the current distribution on the monopole.
3. Calculate the far-field radiation pattern based on the current distribution.
4. Compute the input impedance of the monopole.

Here is a simplified MATLAB script outline to give you an idea of how you might start:

% Define physical constants
epsilon_0 = 8.854187817e-12; % Vacuum permittivity (F/m)
mu_0 = 4*pi*1e-7; % Vacuum permeability (H/m)
c = 1/sqrt(mu_0*epsilon_0); % Speed of light (m/s)

% Define monopole properties
h = 1; % Height of the monopole (m)
f = 10e6; % Operating frequency (Hz)
lambda = c / f; % Wavelength (m)
k = 2*pi / lambda; % Wave number (rad/m)

% Define lossy ground properties
epsilon_r = 15; % Relative permittivity of the ground
sigma = 0.005; % Conductivity of the ground (S/m)
epsilon = epsilon_r * epsilon_0 - 1i*sigma/(2*pi*f); % Complex permittivity

% Define discretization parameters for the monopole (Method of Moments)
N = 100; % Number of segments to divide the monopole into
dz = h / N; % Length of each segment

% (The following steps are placeholders and require the actual numerical
% implementation of the Method of Moments and other calculations.)

% Step 1: Calculate the impedance matrix (Z) for the monopole
Z = zeros(N, N); % Placeholder for the impedance matrix

% Step 2: Calculate the excitation vector (V)
V = zeros(N, 1); % Placeholder for the excitation vector

% Step 3: Solve for the current distribution (I)
I = Z\V; % Placeholder for the current distribution

% Step 4: Calculate the far-field radiation pattern based on I
% (Placeholder for radiation pattern calculation)

% Step 5: Compute the input impedance of the monopole
% (Placeholder for input impedance calculation)

% Visualization and analysis of results
% (Placeholder for plotting and analysis)

I hope this helps!

Best Regards,

Abhishek Chakram

[Robert Achatz]

Thank you for your help. I am keeping this question open in the event someone in the community has already implemented the approach you have suggested.