Topological Broadband Reciever Protectors based on High Order Exceptional Point Degeneracy

Reciever Protectors (RPs) are essential devices for protecting vulnerable circuitry from damage due to high-power sources. Conventional RP designs often suffer from narrow operational bandwidths and low damage thresholds, restricting their application and reliability. We introduce a broadband reflective RP (BRRP) design that leverages high-order exceptional point degeneracy (EPD) of reflectionless scattering modes (RSMs) to achieve broadband transmission and subsequent limiting action while also enhancing the BRRP damage threshold. The extreme broadening is achieved at a 6th order EPD due to simultaneous parity-time (𝒫𝒯) symmetry and chiral-time (𝜒𝒯) anti-symmetry where the corresponding RSMs are in the exact phase of both anti-linear operators. Theoretical analysis and simulations have been performed using Coupled Mode Theory and Computer Simulation Technology microwave studio software, respectively. The experimental platform consisted of evanescently coupled high-Q resonators within a parallel plate waveguide and interrogated by kink antennas via a vector network analyzer. The experiment was performed in the 4-5 GHz range, showing close agreement with the modeling, and limiting action was demonstrated via in-situ perturbations. Future integration of suitable nonlinear elements (e.g., meta-atom embedded with varactor diode) will enable true self-induced BRRP functionality, significantly advancing the capability for device protection against high-powered sources.