Analysis of Basic Delta Loop Antenna over Ground

This example shows how to analyze the performance of a delta loop antenna over a metal ground. The length of the antenna is λ/3 on each side of the triangle, where λ is the wavelength. Equilateral delta antennas are single-band high frequency (HF) antennas. You vary the baseline parameters of an antenna such as the length and height above the ground to optimize antenna performance [1].

Define Basic Dimensions of Shape

Create the delta loop antenna using defined geometry parameters. Use strips instead of wires to create the antenna. Use the cylinder2strip function to calculate the equivatent strip dimesnions.

wireRadius = 1.5e-3;
stripWidth = cylinder2strip(wireRadius);

Create Triangular Strip

Create a triangular strip using a circle shape. Define inner and outer radii. Create circles with three points each using the calculated radii.

otRadius = 0.5774*15.06; % Outside radius of circumcircle of triangle
inRadius = 0.5774*(15.06-stripWidth); % Inside radius of circumcircle of triangle (less than outside radius by strip width)
ot = shape.Circle(Radius=otRadius, NumPoints=3); % Outside Triangle
in = shape.Circle(Radius=inRadius, NumPoints=3); % Inside Triangle

Create a metal strip by subtracting smaller triangle from the larger one. Rotate the strip vertically to place it over the flat ground.

triStrip = ot - in; % Triangular strip
show(triStrip)
title("Triangular Metal Strip");

[~] = rotate(triStrip,90,[0 0 0],[0 1 0]);

Add Metal Ground

Create a metal ground and place the strip above the ground. Add two shapes and visualize the resultant shape.

gnd = shape.Rectangle(Length=60,Width=60);
[~] = translate(gnd,[0 0 -24.5]);
ant = triStrip + gnd;
show(ant)
title("Triangular Metal Strip over Ground");

Create Delta Antenna

Use the customAntenna function to convert the triangular metal strip with ground to an antenna. Add feed to this antenna at a desird location.

ca = customAntenna(Shape=ant);
ca.createFeed([0,0,-8.0819],1);
show(ca)

Analyze Delta Antenna

Calculate and plot the reflection coefficient and impedance of the delta antenna.

Plot Reflection Coefficient

Plot the reflection coefficient for this antenna over the 5 MHz to 10 MHz frequency band with a reference impedance of 50 ohms.

sparam = sparameters(ca,linspace(5e6,10e6,200));
rfplot(sparam);
title("Return Loss of Delta Loop over Metal Ground");

Plot Impedance

Calculate and plot the impedance for this antenna over the 5 MHz to 10 MHz frequency band. The reactance is close to zero at 7 MHz.

impedance(ca,linspace(5e6,10e6,200))
title("Impedance of Delta Loop Antenna over Metal Ground");

Conclusion

In this example, you build and analyze the basic structure of the delta loop antenna over a metal ground. The results closely match to the design expectation.

References

[1] Herwade, Pranita A., and Sandeep V. Gaikwad. “Design of Broadband Delta Loop Antenna and Balun for Ionosonde Application.” In 2015 Annual IEEE India Conference (INDICON), 1–5. New Delhi, India: IEEE, 2015. https://doi.org/10.1109/INDICON.2015.7443498.