A Wide-Angle Scanning Circularly Polarized Concentric Ring Array With Large Element Spacing

A wide-angle scanning circularly polarized (CP) concentric ring array (CRA) with large element spacing is proposed. With large element spacing, 75% of transmitter/receiver components (T/Rs) can be saved compared with a traditional compact uniform array. In addition, two-unit elements are adopted to improve the aperture efficiency of the CRA. Meanwhile, sequential rotation technology and specially designed radiating units are employed to achieve wide axial ratio (AR) bandwidth and wide gain bandwidth of the CRA. To verify the proposed method, a 64-element CP CRA working in a frequency band of 7.15 GHz to 8.65 GHz (19%) with an average element spacing of $1{\rm{\lambda }} \times 1{\rm{\lambda }}$ is designed, fabricated, and measured. The CRA can scan from $ - \text{50}^\circ $ to $\text{50}^\circ $ in the elevation plane for all azimuth directions with AR less than 4.2 dB, scan loss less than 6.9 dB, and aperture efficiency in the Zenith direction higher than 44.7%.