Mechanical Beam Steering Method for X-band Reflectarray Antenna

Abstract

This paper proposes a mechanical beam-steering technique in which the feed horn antenna is moved along an arc trajectory above the reflectarray aperture. To implement this concept, a circularly polarized reflectarray antenna operating in the X-band (8.2 GHz) was designed. The reflecting surface consists of 393 unit cells arranged in a circular configuration, and a reflection phase tuning range of approximately 310° was achieved by adjusting the radius of the metallic ring in each unit cell. Based on this phase range, the antenna was configured to produce the required phase distribution for each incident angle as the feed moves along the designed arc path. To optimize the antenna performance, the electromagnetic characteristics associated with various design parameters were thoroughly analyzed. First, the conventional linear feed movement method was compared with the proposed arc-type movement to quantitatively evaluate phase errors and aperture illumination variations under beam deflection. In addition, the nonuniform distribution of incident angles across the aperture caused by changes in feed position, and its influence on the reflection-phase response and radiation patterns, were investigated. The results confirmed that the proposed arc-based movement maintains relatively small phase errors and stable aperture illumination even over a wide steering range. Simulations demonstrated that the designed antenna achieves a peak gain of 26.2 dBi and an aperture efficiency of 44%, enabling continuous beam steering from 0° to 60°. For experimental validation, the metasurface substrate was fabricated and its radiation characteristics were measured inside an anechoic chamber. During measurement, the feed horn was manually moved along the arc trajectory to replicate the incident-angle conditions used in the simulations, while the F/D ratio was fixed at 0.5. A simple test fixture was fabricated to align the feed and metasurface, incorporating only basic height and angle adjustment features and minimizing electromagnetic interference within the measurement environment. The measured radiation patterns showed good agreement with the simulation results.