An active multifunctional metamaterial with four operating modes

To improve the flexibility and integration of conventional metamaterials, active multifunctional metamaterials (AMMs) have been intensively investigated in recent years. In this paper, a simple but efficient methodology based on equivalent circuits model (ECM) is proposed to design AMMs with four operating modes. The device can be electronically switched between reflective linear-to-linear polarization converter (RLTL-PC), absorber, frequency selective surface (FSS) and transmissive linear-to-circular PC (TLTC-PC) modes. Further, a unit cell (UC) structure consisting of a resistive layer and a double-layer FSS is designed according to the ECM. The operating mode is controlled by electronically tuning the states of PIN diodes attached on each layer. The results achieved with ECM calculation are validated against full-wave simulation and a prototype of the proposed AMM is also fabricated and experimentally tested. This work is promising in seeking the all-in-one solution for practical AMM.