Single-Layer, Dual-Port, and Dual-Mode Antenna With High Isolation for WBAN Communications

In this letter, a single-layer, dual-port, and dual-mode antenna with high isolation between the ports is suggested. This antenna consists of a short-circuited ring patch antenna that surrounds a substrate integrated waveguide (SIW)-based circular cavity in the center. An annular-ring slot is etched on the upper surface of the circular cavity and constitutes a cavity-backed annular ring slot antenna. Dimensions of the antenna are chosen in a way that TM₂₁ mode and TM₁₁ mode are placed at the frequency of 5.8 GHz for the short-circuited ring patch antenna and SIW cavity-backed antenna, respectively; the former has an omnidirectional radiation pattern and the latter has a broadside radiation pattern. Due to having two rows of vias, one for the short-circuited ring patch antenna and the other for SIW cavity-backed antenna, the isolation between the two ports is excellent owing to reduced surface waves. The measurement results of a fabricated prototype are properly consistent with the simulation results. This antenna is an appropriate option to be used in wireless body area networks for having simple structure, dual-mode, single-frequency, and high isolation.