In this example, we present a self-filtering horn antenna for satellite communications. The antenna uses a WR-62 (15.8 x 7.9) radiator. The self filtering properties are established by the use of a small bi-omega particles placed in the mid-way of the antenna's waveguide. These particles causes the antenna to operate at a very narrow bandwidth around 12.6 GHz. At this frequency band, the antenna shows as much radiation performance as a WR-62 radiator. The next figures describe the structure of the antenna and the slab.
Figure 1 - the structure's 3D view in SolidWorks
Figure 2 - the structure's dimensions
Figure 3 - The bi-omega particles' structure
In a first step, we can simulate the antenna's behavior without particles. SolidWorks multi-configuration feature allows us to create several configurations: for example, one for the antenna with the slab and another without it. Then, we can create an HFWorks study for each configuration and leave them to run.
The bi-omega particles are assimilated to a filter. Thus, we can simply simulate them in the WR-62 waveguide to observe their role and ignore the flaring of the antenna: this will reduce the simulation time and memory requirements.
The antenna is made up of a 1 mm PEC metal. The port is applied to the lateral small face of the horn antenna. The omega particles are treated as a PEC printed on a GML 2032 body (Er=3.2 ; Tand= 0.0029).
The antenna's port The conductor on the slabThe slab through the screen's slit
The mesh element size should not exceed one tenth of the free space wavelength. As for the slab's conductor, we should have a finer mesh because it has a small thickness of 35 microns and curved shapes.
The antenna's return loss has a sharp curve around 12.6 GHz. A fast sweep simulation can give an approximate S11 plot. The next figures shows the simulated S11 of an HFWorks discrete sweep frequency plan:
Figure 4 - Simulated return loss (HFWorks)
By using the section clipping feature of HFWorks, we can view the electric field distribution in the inner areas at the intended frequency. We can also view the electric field on isolated parts or bodies.
Figure 5 - Electric field inner distribution
The results were gathered and illustrated in one single plot to compare HFWorks' simulation and measurements. This plot highlights the filtering role of the bi-omega particles.
Figure 6 - Simulated and Measured return loss
As we can see, the simulated results show good agreement with the measured ones . We note that we used the Scattering Parameters solver to compute the return loss and that we can use the Antenna solver if we want to plot radiation patterns or compute the the antenna's parameters such as the gain, the axial ratio... etc.
 Self-Filtering Low-Noise Horn Antenna for Satellite Applications Filiberto Bilotti, Senior Member, IEEE, Luca Di Palma, Davide Ramaccia, and Alessandro Toscano, Senior Member, IEEE