A wide‐angle beam scanning circularly polarized, tightly coupled dipole array based on two‐layer parasitic ring structure elements

Abstract

In this paper, a wide-angle beam scanning circularly polarized (CP) phased array element, which consists of a concentric tightly coupled dipole array (TCDA) element with a two-layer parasitic ring structure and a wideband 90° phase shifter, is proposed. To solve the problem of the scanning blindness zone caused by a concentric layout, the grounded coupling patch for the traditional TCDA element is ‘split’ into a combination of a grounded parasitic ring and coupling patch. This combination structure can not only suppress the in-band common-mode resonance but also destroy the scanning blind zone mode formed by the dipole and grounded coupling patch. In addition, a two-layer parasitic ring structure is introduced to obtain a wider axial ratio (AR) beamwidth relative to a single-layer structure, so a wide-angle beam scanning AR is realized. An 8 × 8 left-handed CP planar array based on the proposed wide-angle beam scanning CP elements is designed and prototyped. Results show that the array can operate over a 3.2:1 (3.75–12.0 GHz) overlapping bandwidth, meeting an AR < 3 dB in the main beam and an active voltage standing wave ratio <2.8 within a ±60° angle scanning range.