A Compact Ultra-Wideband Planar Printed Bow-Tie Quasi-Yagi Antenna with Rhombus Director and Tapered CPS Connection Structure

Abstract

ABSTRACTA compact ultra-wideband (UWB) planar printed bow-tie quasi-Yagi antenna is proposed and experimentally studied in this paper. It is composed of three wideband configurations: micro-strip-line to slot-line transition structure with a shorting vias (balun), a pair of bow-tie driver, and rhombus director, which aims at breaking the bandwidth limitation of the conventional micro-strip (MS) quasi-Yagi antenna. To further improve the impedance matching, the tapered co-planar strip-line is adopted between the bow-tie driver and the balun as bridge. The overall size of the proposed antenna is only 30 mm × 27 mm. A prototype UWB quasi-Yagi antenna is fabricated and measured to verify the validity of this design. The measured impedance bandwidth, defined by −10 dB reflection coefficient, can reach an operating bandwidth of 101% from 3.62 to 11 GHz, over which the antenna exhibits excellent end-fire radiation with a front-to-back ratio of greater than 19 dB and a moderate gain of better than 3.81 dBi. In contrast to the conventional micro-strip quasi-Yagi antenna design, our proposed antenna features a smaller size and wider −10 dB reflection coefficient bandwidth.