Dual-Polarized Slot-Coupled Microstrip Antenna Array With Stable Active Element Pattern

A dual-polarized slot-coupled microstrip antenna array with stable active element pattern is investigated. The antenna element of the array is a slot-coupled microstrip antenna with a reflector. The effect of the ground size on the radiation pattern of the antenna element is analyzed based on the electric field and current distributions. The method of adding copper pillars around the antenna element is proposed to mitigate the influence of the ground plane. A prototype of ${1} \times {3}$ microstrip antenna array is fabricated and measured. Its measured impedance bandwidth for $\mathrm{VSWR} < {2}$ is 520 MHz (1.69–2.21 GHz). Within the operating band, the performances of low mutual coupling, low cross polarization, and stable active element pattern are achieved.