Compact loop‐dipole composite antenna with wideband operation and dual polarization

Abstract

AbstractA design of the antenna with dual diagonal polarizations for 2G/3G/LTE base station applications is first described in this paper. The antenna has a compact size, and its structure is mainly composed of two orthogonally situated dipoles fed with coaxial baluns, a cross strip mounted on the dipoles, and a planar reflector. The cross strip can be regarded as dual orthogonal loop antennas. By embedding thin slots into the loop‐dipole composite antenna, the impedance bandwidth for return loss less than 15 dB can cover the frequency band from 1.7 to 2.7 GHz. Because the adopted balun also serves as an impedance transformer, the cross polarization level at the broadside is lower than −30 dB for all operation frequencies. Then, we found that by varying the dimensions of the slot, the loop‐dipole composite antenna can also deliver a 70% impedance bandwidth for return loss less than 10 dB, and the cross polarization level is lower than −25 dB in whole E‐plane and H‐plane. Antenna prototypes are constructed, and experimental and simulated results have good agreements.