Gain optimization for millimeter wave reflectarray antennas based on a phase gradient approach

Abstract

This paper is concerned with reflectarray antenna design with multiple unit cells in order to enhance the gain at the design frequency, while keeping an acceptable bandwidth to work for 5-G mobile base station applications. The design is based on five unit cells. The design begins with an investigation of the phase responses of all unit cells. It is required to choose a unit cell that can span 360° with linear characteristics. Unfortunately, none of the unit cells has perfectly linear phase characteristics. Each of them has a limited linear phase region. The proposed reflectarray design method selects the most linear region from each phase curve for selecting the appropriate unit cell with the appropriate size for each required phase using a phase gradient approach. With this approach, piece-wise linear phase characteristics are adopted for the design of the reflectarray to enhance the gain at the design frequency.