Design of a Compact Broadband X-Band Reflectarray Antenna Using an Archimedean–Sinusoidal Hybrid Element

Abstract

This letter proposes a single-layer X-band reflectarray antenna employing an Archimedean–sinusoidal hybrid element in a subwavelength configuration. By integrating sinusoidal perturbations into four-arm Archimedean spirals, the unit cell achieves an extended reflection-phase range (~550° at 10 GHz) and improved phase linearity while maintaining a compact 0.4λ₀ periodicity. To enhance the bandwidth, a Vivaldi antenna is employed as the feed source, ensuring reflection coefficients below − 10 dB across the X-band. By arranging mirror-symmetric elements, the cross-polarization of the reflectarray is effectively suppressed. An 11 × 11 prototype antenna was designed, fabricated, and measured, achieving a peak gain of 18.9 dBi at 10.4 GHz. The measured 3-dB gain bandwidth is 30.7% (8.29–11.36 GHz), and the measured cross-polarization and sidelobe levels are − 20.8 dB and − 7.1 dB, respectively.