Reconfigurable Intelligent Surface Design using PIN Diodes via Rotation Technique – Proof of Concept

In this paper, we present the design of a reconfigurable intelligent surface (RIS) operating in the Ka-band (27 – 31GHz). The considered RIS operates in reflection mode; thus, it is a reflectarray antenna. The reflectarray unit cell has a relatively simple structure with four metal layers and two Isola Astra MT77 substrates. In order to achieve the electronic phase control of the unit cell, two p-i-n diodes were integrated on the reflecting patch. The alternation of the diodes states will create a rotation in the current distribution on the top of the reflecting patch, and thus a 1-bit phase shift resolution is obtained. The unit cell performances present 1.5 dB losses over the studied band (14% of relative bandwidth). The phase difference between the two unit cell states is 180° at the central frequency with acceptable phase errors over the frequency band. The designed unit cell is then used in the synthesis of reflectarray antennas. For this purpose, an in-house synthesis tool is developed to optimize the reflectarray analytically. Furthermore, an 8×8 elements reflectarray is designed using the aforementioned tool, and its theoretical results are compared to a full-wave simulation.