2-D Photonic Crystal Leaky-Wave Antennas: Theoretical Investigation and Design Approaches

The electromagnetic radiation from an electric line source embedded within dielectric photonic crystals is thoroughly investigated in this contribution. The structures analyzed consist of periodic chains of circular voids in dielectric media. We demonstrate the potential utility of these holey lattice structures in the design of leaky-wave antennas that show high directivity. The radiation mechanism of two-dimensional (2-D) dielectric lattices has been investigated in terms of leaky modes [1], presenting a method based both on the analysis of the band diagrams of the Bloch waves propagating in the 2-D photonic crystals (PCs) and the leaky-wave investigation of open waveguides. This study provided an insightful perspective on antenna design. In [2] the leaky-wave radiation from bisected Dielectric Rod Photonic Crystals (DRPCs) and Holey Photonic Crystals (HPCs) was investigated. Bisected DRPCs consist of two-dimensional periodic chains of circular dielectric rods in free space and over a metal plate, while HPCs involve air columns drilled in a dielectric host medium. It was found that HPCs are the optimal choice for achieving high directive radiation, outperforming dual structures based on DRPCs by 6 dB in terms of directivity. In this contribution, further details on the working principle and guidelines for the design of highly directive HPC leaky-wave antennas (HPCLWAs) bisected by a metal plate are provided. In particular, it is shown how high directivity is maintained even when the relative permittivity of the hosting dielectric medium is decreased and the total band gap of the 2-D PC vanished. Indeed, even in the absence of a complete stopband in the 2-D PC band diagram, it is still possible to design a directive HPCLWA, by carefully investigating the leaky and bound modes of the relevant open waveguide. This original finding holds significance in manufacturing, as it enables the utilization of cost-effective methods like three-dimensional (3-D) printing. An example of HPCLWAs, designed to operate at f = 24 GHz and excited by a simple probe source, is shown in Fig. 1. More details will be shown at the conference.