# Design of a 3-Bit Circularly Polarized Reconfigurable Reflectarray
## 1 Introduction
In recent years, scholars at home and abroad have focused on studying the implementation schemes of various reconfigurable reflectarray antennas, including mechanical regulation [19; 20; 21; 22], electronic control [23; 24; 25; 26; 27], and loading novel materials [28; 29; 30]. In 2022, [PERSON] et al. proposed a mechanically reconfigurable reflectarray with reflection phase control. This reflectarray consists of a rectangular microstrip patch unit and a support connection structure made of polylactic acid. The central operating frequency is 16 GHz, and the height of the unit is adjusted by the support connection structure. Different heights result in different phase differences, by which it can enable the modulation of the reflection phase [31]. In the same year, [PERSON] et al. published a 1-bit wideband reconfigurable reflectarray in Ku-band [32]. This reflectarray utilizes a 1-bit phase shifter with a microstrip line structure loaded with a PIN diode. The reflection phase is regulated by a receive-phase-shift-transmit structure, allowing for a beam scanning range of \(\pm 50^{\circ}\) in the azimuthal plane and \(-20^{\circ}\) to \(50^{\circ}\) in the elevation plane. In 2021, [PERSON] et al. proposed a Ku-band dual-bandwidth circularly polarized reconfigurable reflectarray [33]. The reflector unit proposed consists of two ring resonant structures with similar shapes but different sizes. Both ring resonant structures are loaded with four varactors and operate in two frequency bands. By electrically adjusting the capacitance of the varactor, the resonant frequency of the ring resonant structure can be changed, and the phase response can be changed. This design aims to achieve a beam scanning range of \(\pm 50^{\circ}\). In 2020, [PERSON] et al. proposed a light-controlled programmable metasurface [34]. The unit structure is loaded with a varactor, and the DC bias circuit is located at the back of the metasurface, which is composed of a PIN diode. When the light shines into the circuit, the circuit will be converted into different DC voltages according to the strength of the light, and then the control of the varactor can be achieved. In the same year, [PERSON] et al. proposed a thermal sensing programmable metasurface [35] in which the unit phase shift is controlled by the on-off of a PIN diode, and the DC bias circuit of each PIN diode is connected to a row of thermistors. By adjusting the distribution of heat source intensity, the reflected beam can be regulated. Currently, there are many research studies on linear polarized reconfigurable reflectarray, but there are few research studies on circular polarized reconfigurable reflectarray antenna, especially on multi-bit circular polarized reconfigurable reflectarray. In this study, a 3-bit circularly polarized reconfigurable reflectarray was designed by using the phase shift principle of the rotating element structure and loading phase delay line on a circular metal patch, which provides technical support for the research of multi-bit circular polarimetric reconfigurable reflectarray. The contributions of this paper are as follows: (1) A 3-bit circularly polarized reconfigurable reflectarray is proposed. (2) Based on the phase-shifting principle of the rotating element structure, the design of the circularly polarized reconfigurable reflectarray is realized by loading phase delay line on the circular metal patch. (3) The proposed 3-bit circularly polarized reconfigurable reflectarray has the advantages of low loss, high aperture efficiency, a wide beam scanning range, and excellent stability in wide-angle oblique incidence.