Tunable SIW-Based Evanescent-Mode Cavity-Backed Slot Antenna With Contactless Tuning

This paper presents a frequency reconfigurable evanescent-mode cavity-backed slot antenna (ECBSA) with a wide tuning range, high-power handling capability, and simplified manufacturing. The tuning mechanism consists of external long-range linear actuators and a contactless tuner disc to vary the capacitive loading of an evanescent-mode cavity. The antenna's operating frequency is tuned by changing the cavity's critical gap size. Radiation occurs through an annular slot aperture on the cavity's ground plane. The design is realized on a printed circuit board (PCB) using substrate-integrated waveguide (SIW) technology to facilitate easier system integration with other planar circuits. The fabricated prototype of the antenna shows 40% tuning from 1.71-2.58 GHz when the contactless tuner is displaced vertically across a distance of 508~\mu \text{m} . Measurement results for the peak realized gain of ECBSA is as high as 5.48 dB at the maximum operating frequency of 2.58 GHz. Due to a larger range of the cavity's critical gap sizes, achieved using external linear actuators, the power handling capability is higher than the typically used piezoelectric disk tuners in ECBSA design. The proposed antenna also exhibits the largest tuning range among the high-power mechanically-tuned cavity-backed slot antennas presented in the literature.