Compact single-varactor diode frequency-reconfigurable microstrip patch antenna

Abstract

A single-varactor frequency-reconfigurable microstrip patch antenna is presented. The antenna comprises a symmetrical arrangement of four metallised patches coupled and interconnected via slots and metallic bars, respectively. The antenna structure is excited through a single feed probe connected to one of the patches. To achieve a compact size of 22 × 21 × 1.57 mm, a shorting pin is placed close to the feed point to pull down the antenna's resonant frequency. By adding a varactor diode at the centre of the patch, frequency reconfigurability is introduced. Variation in the varactor's DC reverse bias voltage from 0 to 7.5 V results in a corresponding resonant frequency shift from 1000 to 1150 MHz, thus providing a tuning range of 15%. The proposed design is compact and achieves frequency reconfiguration with a single-varactor diode and a low bias voltage requirement compared with the design characteristics reported in existing works. The antenna can find application in various existing and emerging communication systems.