Reflectarray antenna design

The process of reflectarray antenna design can be usually carried out into two separate steps: element design and aperture phase distribution design. In the step of element design, reflectarray elements need to be devised based on the requirements of phase range, element bandwidth, polarization and so on. Then, different methods can be employed to analyze and predict the reflection phase for a given geometry of reflective element within reflectarray structure, such as TEM waveguide approach, infinite array method or quasi-periodic model with forced linked boundary conditions (FLBC). In the process of aperture phase distribution design, the desired aperture phase distribution can be derived though ray tracing principle, conjugated field matching (CFM) technology or optimization techniques such as alternating projection algorithm (APA) and particle swarm optimization (PSO) to satisfy the design specifications. Then the geometrical features of individual element in the reflectarray aperture need to be adjusted properly to match the desired phase distribution. It is noted that during this step of phase matching, effects of oblique incident angle for edge elements should also be taken into account especially for low-profile reflectarrays or offset configurations, based on the superposition of TM and TE wave incidences. Additionally, the multi-point phase matching method (PMM), where the achieved phase shifts of the array elements match the desired phases at multiple frequencies, can be employed to achieve wideband performance [1]. It is noted that PMM can also be extended to design dual-band reflectarray in frequency domain [2], circularly polarized reflectarrays with low axial ratio in polarization domain [3], and wide-angle beam scanning reflectarray in spatial domain. Finally, due to no specialized software dedicated to analysis of reflectarrays, full-wave electromagnetic software such as HFSS, CST, and FEKO can be applied to obtain accurate radiation characteristics of reflectarray antennas. In particular, FEBI or datalink option in HFSS can be used to reduce computing resource. Other analysis methods such as array-theory approach and aperture-field approach can also be employed to analyze and derive the radiation performances of the reflectarrays with reduced computational time and resources at the expense of accuracy [4]. © 2017 IEEE.