A high selectivity planar filtering quasi‐Yagi antenna

Abstract

A high selectivity planar filtering quasi-Yagi antenna employing the codesign of bandpass filter (BPF) and antenna is investigated in this article. A stub-loaded resonator (SLR) and a half-wavelength resonator are utilized as the feeding network to excite the driven dipole of the quasi-Yagi antenna. The length of the driven dipole is about half-wavelength, which can be equivalent to the last stage resonator of BPF, achieving a good filtering gain response. To improve the frequency selectivity, an elaborate balun structure is utilized, and a transmission zero (TZ) on the lower side of the passband is acquired. Together with the TZ introduced by the SLR at the upper edge, the antenna can achieve a sharp band-skirt. An antenna prototype is fabricated and measured, showing a wide bandwidth up to 19.1% (from 3.1 to 3.76 GHz) with a flat gain response in band, an antenna peak gain of 4.85 dBi and a peak efficiency of −0.6 dB.