Design of a Contactless AF-SIW Horn Antenna with Compact Size and Enhanced Directivity

This work presents an H-plane contactless air-filled substrate integrated waveguide (CLAF-SIW) horn antenna, whose directivity is enhanced by incorporating a metasurface along the horn flaring. CLAF-SIW structures allow efficient and cost-effective handling of the propagation zones to incorporate metasurfaces. In this way, it is possible to reduce phase errors at the aperture, a common issue in horn antennas. The metasurface is designed using substrate integrated hole (SIH) unit cells with a patch based on parallel plate waveguides (PPW). An analysis of the distribution of the unit cells along the horn antenna is conducted to obtain the equivalent effective refractive indices required in the metasurface. By varying the size of the hollow where the metal patch is located, the equivalent refractive index for the propagating mode of the PPW can be tuned. The directivity achieved is comparable to that of a horn antenna with optimal dimensions, but with a 41% reduction in length. The simulated results demonstrate an impedance bandwidth below −10 dB from 32.8 to 49.7 GHz, with a directivity above 12 dBi.