A Physical Insight Into Reconfigurable Frequency Selective Surface Using Characteristic Mode Analysis

In this letter, we provide a physical insight into the operating mechanism of a reconfigurable bistate active frequency selective surface (AFSS) based on characteristic mode analysis. At first, we study the modal behavior of the unit structure under different load resistances and found that the modal significance bandwidths of the fundamental mode and the high-order modes increase with the load resistance. When the load resistance is very high, the fundamental resonant frequency will move to high frequencies and the high-order modes may not change. Such features can be used in the design of the reconfigurable transmission/reflection frequency selective surface. It is found that the isolation between transparent and reflective states is mainly determined by the radiated field from fundamental mode. At the same time, we provide two improvement approaches to design this kind of frequency selective surfaces. And a reconfigurable AFSS operating at 2.1 GHz is designed, fabricated, and measured. The letter makes sense for the design of reconfigurable bistate AFSSs.