Fluctuated Impedance Design Method for Multistate Fusion of Broadband Reconfigurable Absorbers

The limitation between the tunable bandwidth and the number of states greatly restricts the application and development of reconfigurable absorbers. Therefore, the fluctuated impedance design (FID) method is proposed for the first time to provide a solution for reconfigurable absorbers with few states. The point of FID is to introduce fluctuation factors (FFs) to disrupt the monotonicity of impedance, creating multiple susceptance offset points to achieve multistate fusion. The working principle of FID was analyzed by equivalent circuit model. Simulations of the surface field distribution illustrate its physical mechanism. Through the reconfigurable property of the PIN diode, the FID absorber covers a tuning absorption band from 0.72 to 5.84 GHz using only two states. Multiple absorption peaks at low frequencies are fused into one broadband low-frequency absorption state with the percentage bandwidth expanded to 64.2%. The thickness is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.048\lambda _{L}$ </tex-math></inline-formula> (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{L}$ </tex-math></inline-formula> is the wavelength of the lowest operating frequency).