Broadband Dual-Polarized Dual-Dipole Planar Antennas: Analysis, Design, and Application for Base Stations

Abstract

In this article, we propose a compact ±45° dual-polarized dual-dipole (DPDD) antenna for second-, third-, and fourth-generation (2G/3G/4G) long-term evolution (LTE) base stations. The antenna consists of two perpendicularly crossed dual-dipole elements. Each dual-dipole element is directly fed by a coaxial cable. Two dual-dipole elements are printed on the same substrate, making the antenna planar and compact. Due to the coupling between two crossed dual-dipole elements, the antenna can achieve a broad bandwidth of 51% for a return loss greater than 15 dB (1.61-2.71 GHz) with a high isolation of 30 dB. The dual-polarized antenna has a gain of 9 dBi and a halfpower beamwidth (HPBW) of 65 ± 5° for ±45° polarization with a flat metallic reflector. For applications in LTE700/GSM850/900 base stations, a new artificial magnetic conductor (AMC) surface is introduced to replace the metallic reflector. It is shown that the antenna height can be significantly lowered from 105 mm (0.29λ0.83, where λ0.83 is the freespace wavelength at the frequency of 0.83 GHz) for a metallic reflector to 31.52 mm (0.087λ0.83) for an AMC surface while a broad bandwidth of 52% (0.68-1.16 GHz) is still achieved. The broadband ±45° antenna is described in the Broadband ±45° section, and the ±45° antenna with an AMC surface is demonstrated in the DPDD Antenna with an AMC Surface section.