Broadband reflectarray antenna using circular ring additional helical microstrip lines

Abstract

This article proposes a new type of single-layer unit aimed at improving the operating bandwidth of reflectarray antennas (RA). Specially, the novel element comprised of a circular ring patch combined to four helical microstrip lines (HMLs), where the rotation angle of each HML around the center of the circular ring differs by 90°. The optimized unit can achieve a linear phase response of 400° phase at 10 GHz. Additionally, the phase response curves remain nearly parallel over the 8–13 GHz band, so that using the unit as a broadband reflector antenna in the X-band is an effective means. Finally, an octagonal aperture center fed reflectarray antenna consisting of 464 elements was designed and tested. The test results indicate that the designed RA achieves a 1-dB gain bandwidth of 35.5 % from 8.8 to 12.6 GHz. In addition, the sidelobe level for the E-plane is tested to be below −19 dB at 10 GHz.