A Functional Antenna Tuner for Slot Patch Antenna

Abstract

Abstract-In this paper, without using external power and active components, a design of pin coupled functional antenna tuner is presented. The tuner consists of two parts, a coupling pin and a tuning circuit. It is used to tune the bandwidth and antenna gain of the proposed slot patch antenna. The prototype, including a slot patch antenna and the tuner, was constructed and excited through a T-shape microstrip feed circuit resonated at 2.6 GHz. The impedance bandwidth BW (−10 dB return loss) of the slot patch antenna without coupling to the tuner was 3% referred to the operation frequency at 2.6 GHz. When the tuner was matched with the impedance 75 Ω through the coupling pin to the proposed antenna, the BW of the antenna was increased to 11% operated at 2.6 GHz. However, if the tuner was matched with the impedance 25 Ω to the proposed slot patch antenna, the impedance bandwidth of the antenna was increased 21% at operation frequency. Relatively uniform antenna gain was obtained when the matching impedance was decreased from 75 Ω to 20 Ω. In the meantime, the lower matching impedance corresponds to more reducing cross-polarization of the proposed slot patch antenna can be observed in the measured field patterns.