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

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.