Frequency Agile Slot Antenna Using Contactless Capacitive Loading

Abstract

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.

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

“…Mechanical tuning elements like metallic tuning screws [10] or posts [11], and piezo-enabled tuners [12], [13] can be used to attain frequency-agility with high power handling and high linearity, unlike the semiconductor junction devices. In [13], a mechanically tunable evanescent-mode (EVA-mode) cavity-backed slot antenna (CBSA) is presented with a Power Handling Capability (PHC) of up to 80 W. The EVA-mode antenna's center frequency is tuned by changing the critical gap between the post and cavity ceiling of the EVA-mode cavity with a piezoelectric disk that is bonded onto the cavity [13].…”

“…This tuning method has been applied to design highpower tunable filters up to Ka-Band [16], and in high-power impedance tuners [17]. In [12], contactless capacitive loading was integrated with a slot on a ground plane to achieve octave tunability from 2-4 GHz, with a bi-directional radiation pattern. However, this tuning method has not been investigated in miniaturized cavity-backed slot antennas.…”