60 GHz Electronically Tunable Leaky-Wave Antenna Based on Annular Surface Plasmon Polariton Media for Continuous Azimuth Scanning

This article proposes a single-layered electronically tunable annular surface plasmon polariton (SPP)-based leaky-wave antenna at 60 GHz for continuous azimuthal beam scanning. Initially, the groundless annular SPP transmission line is designed having specialized feeding mechanism which is operational at 60 GHz under SPP mode. Periodic radiating semicircular patches are incorporated into the vicinity of the TL that form an additional momentum caused to convert the slow-wave SP mode to radiating leaky-mode and placement of extra metallic ground makes the radiated beam unidirectional. Furthermore, implementation of the varactor diodes with imposed suitable switching conditions make the geometry electronically tunable to achieve a continuous complete azimuth coverage. The theoretical predictions, numerical simulations and the experimental validations of the proposed structure show good agreement. The proposed antenna show an overall scanning range of 275°, peak gain of 19.9 dBi with average sidelobe level of −10 dB and minimum cross polar level of −20 dB. Availing the benefits from the low-profile compactness and improved performance, the proposed groundless LWA appears as a promising candidate for integration in 60-GHz mm-wave applications.