Dual-Polarized Omnidirectional Antenna with Simple Feed and Ultra-wide Bandwidth

Abstract

A dual-polarized omnidirectional antenna with simple feed and ultrawide operational bandwidth is presented. The antenna is a combination of four vertical monopoles and four horizontal dipoles. The four vertical monopoles are printed on two thin FR4 substrates arranged orthogonally to each other. This arrangement not only makes the design easy to fabricate, but also significantly simplifies the feed and design of the horizontal dipoles. To avoid the feeding intersection, the feedline of the horizontal dipoles is placed at an off-center position. This allows placing three additional metallic posts, which makes the system mechanically stable while preserving the design symmetry for a high isolation. The final design with 0.23 $\lambda _{\text{min}}$ profile was realized ( $\lambda _{{\min}}$ is the free-space wavelength at the minimum operating frequency). An overlapped bandwidth of 78.6% (1.70–3.90 GHz) with a measured isolation of more than 34 dB is achieved. Satisfactory omnidirectional patterns in the horizontal plane in both modes are obtained with the peak gains of 6.9 and 5.4 dBi, respectively.