A NOVEL DESIGN OF FOLDED DIPOLE FOR BROADBAND PRINTED YAGI-UDA ANTENNA

Abstract

In this paper, a printed wideband Yagi-Uda antenna with a novel folded dipole driver is proposed. The folded dipole driver is comprised of a folded dipole and a microstrip feedline which functions as an internal balun to mainly determine its wide impedance bandwidth. With the optimized parameters, an operating band of 1:69GHz » 2:72GHz can be obtained. Besides the folded dipole driver, the broadband printed Yagi-Uda antenna also consists of three directors and a re∞ector. Its wideband performance is mainly determined by the folded dipole driver, while the re∞ector and directors improve its performance slightly. By optimizing the geometrical parameters of the folded dipole driver, a bandwidth of 61.8% (1:53GHz » 2:93GHz) for return loss being higher than 10dB is achieved. The proposed printed Yagi-Uda antenna is realized on FR4 substrate with a measured operating bandwidth of 62% (1:51GHz » 2:94GHz), a ∞at gain (5:6dB » 7:3dB), more than 10dB front-to-back ratio and lower than i15dB cross-polarization level.