A wideband and low-cost square radial line slot array antenna for circularly polarized applications

Abstract

A circularly polarized radial line slot array with enhanced bandwidth is presented in this letter. The proposed antenna consists of two parallel plates, a monopole probe and a spiral slot array. The parallel plates form a radial cavity and is fed by the probe. Then, the spiral slot array etched on the upper substrate can be excited by the radially outward wave to provide broadside radiation. In this design, the side wall of the cavity is left open, which helps to obtain wideband operation and has little effect on radiation patterns. To enhance the bandwidth further, a square cavity is used here to substitute for an initial circular one. With such a structure, the antenna is wide in bandwidth and compact in size. The proposed antenna is designed and fabricated. Measured results reveal that the antenna can provide an impedance bandwidth of 37.2% (15.1–22.0 GHz) and an axial ratio bandwidth of 31.0% (15.0–20.5 GHz), respectively. Additionally, the measured maximum gain is 26.7 dBic at 17.5 GHz.