An Ultrawideband Dual-Polarized Phased Array Antenna for Sub-3–GHz 5G Applications With a High Polarization Isolation

Abstract

A dual-polarized ultra-wideband phased array antenna with a wide scanning range and high isolation polarization characteristics is presented in this paper. A tightly coupled dipole with an etched slot is proposed as the element antenna, which has a low active input impedance in a wideband and a wide scanning range. Thus, a simple feed strategy without requiring additional external matching networks and baluns could be adopted for the designed scheme. To obtain a large polarization isolation, a capacitively-loaded cross-shaped metallic wall is proposed. It is also helpful to improve the in-band matching by mitigating the bandwidth-limiting loop mode at lower frequencies and removing the undesirable common-mode resonance. As a demonstration, an array is designed with a 4.1:1 bandwidth (0.69-2.88 GHz) and an active VSWR < 3.4 while scanning up to ±45° in the E-, H-, and D-planes. Its polarization isolation is better than 45 dB at the broadside and 35 dB within most of the bandwidth when scanning to ±45° in the E-/H-planes. Its cross-polarization level is more than 51 dB at broadside and 40 dB in scanning up to ±45° in the E- and H- planes. A dual-polarized 8×8 array prototype (64 ports per polarization) is manufactured and evaluated. Results from the experiment demonstrate good agreement between the measurement and design. The designed antenna is scalable, has a high polarization isolation, a wide scanning range, an ultra-wide bandwidth, and a low cost.