With the development of modern wireless systems, the spectral environment has become increasingly crowded. This has spawned a strong interest in frequency, bandwidth, and pattern reconfigurable antennas, which can adaptively tune their response to reduce interference. Most recent development in frequency reconfigurable antennas has focused on tuning by use of microelectromechanical systems, pin diodes, or varactors. However, these tuning techniques are ill-suited for high power applications due to breakdown, non-linear effects, and other performance issues. These problems can be solved by the use of mechanical tuning. In this paper, a piezoelectric linear actuator tuned slot antenna is presented. The design is based upon changing the capacitive loading of a slot antenna, and thereby increasing the electrical length, through physical displacement of a metal plate. The antenna was simulated, fabricated, and measured to tune a full octave from 2-4 GHz while maintaining a maximum return loss of greater than 9.0 dB. Simulations also show a 65.74% to 95.75% radiation efficiency across S-band. A broadside realized gain of greater than 1.73 dB was measured over the entire tuning range. Moreover, the tuning mechanism was proven robust above other methods by withstanding up to 100 W of power incident on the feed at 3 GHz.

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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 µm. 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 highpower mechanically-tuned cavity-backed slot antennas presented in the literature.INDEX TERMS Tunable slot antennas, evanescent-mode cavity, high-power, contactless tuning, substrateintegrated waveguide (SIW)