Miniaturization of Omnidirectional Cavity Antennas Using Substrate-Integrated Impedance Surfaces

This communication presents a compact cavity antenna with horizontally polarized omnidirectional radiation pattern. The dimension miniaturization of an omnidirectional resonant cavity is achieved by loading the capacitive substrate-integrated impedance surface (SIIS). Specifically, the SIIS is composed of a row of blind vias that are periodically arranged near the antenna's radiating aperture, effectively providing a shunt capacitance that can be controlled by the insertion depth, period, and diameter of blind vias. The dispersion of the omnidirectional cavity antenna is theoretically studied and the explicit design formula is derived. Our results report that loading the capacitive SIIS can significantly reduce the size of an omnidirectional cavity antenna (52.4%). As a proof of concept, a prototype was fabricated and characterized, with a good agreement between the measurement and simulation results. The results also show that omnidirectional radiation patterns can be maintained well when the operating frequency is tuned, with the realized gain slightly fluctuated between 2.7 and 3.2 dBi. The proposed antenna exhibits potentials in volume-limited omnidirectional wireless communication systems.