A Broadband Dipole Antenna With Parasitic Patch Loading

Abstract

By loading a parasitic patch, a novel broadband unidirectional dipole antenna is presented. The antenna fed by a coaxial balun consists of a folded dipole, a parasitic patch, and a ground plane. The folded dipole has two bowtie elements and a U-shaped structure. In the low operating band, the folded dipole works as an electric dipole and the parasitic patch works as a director. By using the director, the impedance matching performance is improved dramatically. In the high operating band, the two bowtie elements are as an electric dipole, and a magnetic dipole is formed by combining the parasitic patch and U-shaped structure. A new resonant frequency is generated and the impedance bandwidth is enhanced due to the magnetic dipole. Measured results show that an impedance bandwidth of 1.61–3.45 GHz (72.7%) for S 11 ≤ −15 dB is obtained. Stable radiation patterns, low cross polarization, and a maximum gain 8.77 dBi are achieved.