Characteristic Mode Design of Dual-Band Reconfigurable Frequency Selective Surface

In this paper, a characteristic mode design of dual-band reconfigurable frequency selective surface (RFSS) with transmission/reflection band is presented. Through the visualization of modal behavior, the theory of characteristic modes (TCM) is used to guide design from a physical perspective. At first, the dominant modes of two basic structures that have a major impact on reflection are clarified by observing the modal behaviors. The appropriate combination of the two structures forms an initial element with bandpass properties. Then, the positive-intrinsic-negative (PIN) diode is placed in the middle of the microstrip line and as the state shifts from ON to OFF, the dominant mode resonant frequency of the microstrip line shifts upward. Such a feature can be used to design the transmission/reflection RFSS. Experimentally, a dual-band RFSS operating at 8.8 GHz and 10.4 GHz is designed and fabricated. The measured results that agree with the full-wave simulation validate the proposed TCM-based design.