Low Cross-Polarization Level Circularly Polarized Phased Arrays Using a Spiral Sequential Rotation Technique

This letter introduces a novel subarray-configuration method of n × m spiral sequential rotation (SSR) to achieve low cross-polarization level (XPL) and low sidelobe level (SLL) over wide scanning area for circularly polarized phased arrays. Different from the conventional sequentially rotated technique (SRT), the SSR overcomes the problem of high XPL and high SLL that usually arise in the D-plane during wide-angle scanning by disrupting the periodic phase distribution while maintaining a simplified and regular rotation angle. Moreover, the SSR can broaden the 3 dB axial ratio bandwidth as well as the scanning angle, which could be a competitive candidate for the wide-angle coverage satellite application. One prototype of a 4 × 6 cross-dipole array working at 20 GHz has been fabricated, and the measured circularly polarized (CP) patterns are in good agreement with the predicted patterns.