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Quarter Horn Antenna

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Description

Horn antennas are very popular at UHF (300 MHz-3 GHz) and higher frequencies. They are known to have a directional pattern with a high gain. A horn antenna that is flared in the E-plane is called an E-Plane horn, or simply an E horn. This example illustrates a basic model of an ideal horn (dimension around 3000 mm). The solver profits from the model's symmetry by analyzing only a quarter of it.

Quarter Ehorn antenna model (3D SolidWorks view)

Figure 1 - Quarter Ehorn antenna model (3D SolidWorks view)

Simulation

To simulate the behavior of this quarter Ehorn antenna, we create an Antenna study, and specify the relevant frequency range at which the antenna operates (The appropriate range frequencies is around 0.4 GHz. In an antenna simulation, radiation boundaries which are peculiar features of such a simulation are assigned to the surfaces truncating the air surrounding the antenna to simulate an anechoic chamber.

Solids and Materials

The antenna is filled in with air. So, we select all the solids and apply air to them as filling material. The faces of the solids are then treated as Perfect Electric Conductors depending on the relative direction of the electric field.

Load/ Restraint

The port is applied to the small lateral face of the antenna. PEC boundaries are assigned to lateral boundaries. PECS and PEMS boundaries are conveniently assigned to symmetry planes of the model.

Boundaries: Red= Radiation, yellow= PEC, blue= Port

Figure 2 - Boundaries: Red= Radiation, yellow= PEC, blue= Port

The model doesn't have very particular shapes. A uniform mesh of the assembly should be sufficient without any applied mesh controls. Therefore, we specify the number of mesh elements to be created on the diagonal of each solid body.

Results

Animating the 3D electric field's distribution by varying the omega-T angle gives us a hint on how the wave propagates into the port and gets radiated within the horn's flare. We can first have a look at the curve of the reflection coefficient at the port, to decide which frequency yields the best matching.

Wave propagation in the antenna at 0.4 GHz

Figure 3 - Wave propagation in the antenna at 0.4 GHz

This figure shows the variation of the reflection coefficient at the port. As mentioned within the beginning of this report, HFWorks computes Scattering Parameters within antenna studies as well. In this example, the antenna is best matched at 0.9 GHz.

Variations of reflection coefficient at the antenna's port

Figure 4 - Variations of reflection coefficient at the antenna's port

The polar plots cover a wide range of parameters: radiated electric field, radiation intensity, directivity, gain pattern, axial ratio... etc. This is a plot of the radiated electric field (Radiation Intensity) at 0.4 GHz.

Radiated Electric field vector distribution at 0.4 GHz

Figure 5 - Radiated Electric field vector distribution at 0.4 GHz

References

[1] M.S. Narasimhan and V. Venkateswara Rao, "A correction to the available radiation formula for E-Plane sectorial horns", IEEE Trans. Antennas Propagat., vol. AP-21, pp. 878-879, Nov 1973.