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 arises 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 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 20GHz has been fabricated, and the measured CP patterns are in good agreement with the predicted patterns.