Beam-steering reflectarray based on two-bit aperture-coupled reflectarray element

In this paper, a two-bit phase-shifter element for reconfigurable reflectarray antennas is presented. The element is formed by a cut-ring patch coupled to the delay line through an annular slot. The method using a shorting via is applied to this element to separate the line into two delay lines in order that the phase shift can be proportional linearly with respect to the length of two delay lines. The length of each delay line is optimized to provide four-phase states with a step of 90 degrees according to ON/OFF states of two switches. A reflectarray prototype consisting of 8x12 elements has been fabricated and measured to validate the design. Experimental results indicate good characteristics of the reflectarray element and excellent beam-steering capabilities according to the ON/OFF states of the switches.