A Modular Wideband Dual CP Tightly Coupled Phased Array Antenna With 70° Scanning

In this article, the beam scanning range expansion and polarization diversity of a circularly polarized (CP) tightly coupled (TC) phased array are investigated. A systematic theoretical analysis of the scanning axial ratio (AR) is conducted, and guidelines for implementing wide-angle CP beam scanning phased array are provided. Following these guidelines, to achieve similar radiation patterns in the element’s E- and H-planes, a novel method based on the Fourier transform relationship theory is proposed which instructs the element structure design by tailoring its surface current distribution. The influence of spatial phase difference between two orthogonal linearly polarized (LP) waves is analyzed, motivating the adoption of a colocated feed array topology. Furthermore, a wideband coupler is developed, and scanning blindnesses are effectively mitigated. An $8\times 8$ dual CP phased array prototype is simulated, fabricated and measured, which demonstrates good impedance matching and scanning AR performance across the X-band with a beam scanning range up to ±70°. In addition, the proposed array features a fully planar and modular architecture.