High-Gain Photonic Crystal Antenna Based on Tamm Plasmon Polaritons.

To overcome the large size of conventional high-gain antennas and the structural complexity of typical photonic crystal antennas, this paper proposes a cavity-free photonic crystal (PC) antenna driven by microwave-band Tamm plasmon polaritons (TPPs), which eliminates the conventional half-wavelength resonant cavity while maintaining a moderate total height (38.4 mm, ~2.1λ0). The core innovation of this work lies in shifting the gain-enhancement paradigm from traditional bulky, volume-based spatial resonances to a direct 2-D interface feeding strategy. By rigorously satisfying the phase-matching condition between a one-dimensional PC and a highly reflective substrate, a strong TPP mode is excited. Distinct from conventional designs, we embed a simple microstrip patch exactly at this phase-matched boundary to directly exploit the extreme electric field localization of TPPs. This novel mechanism enables a cavity-free architecture that achieves highly directional emission without complex feeding networks or metallic cavities. Simulations and measurements exhibit excellent agreement. At 16.43 GHz, the measured peak gain reaches 16.4 dBi, with 3-dB beamwidths of 13.5° and 18.5°. Ultimately, this TPP-driven paradigm offers a practical solution tailored for advanced wireless communications and radio astronomy.