Topology-Enabled Finite-Band Absorption Framework Based on a Bioinspired Nested Dual-Loop Architecture

The Rozanov limit provides a fundamental causality constraint for passive electromagnetic absorbers, but practical ultrabroadband absorbers are also governed by how efficiently structural topology injects, stores, redistributes, and dissipates the available material loss. Here, we propose a topology-enabled finite-band absorption framework to evaluate structural loss utilization under fixed material and thickness constraints, rather than replacing the classical Rozanov causality theorem. Inspired by the selective transport mechanism of nuclear pore complexes, a nested dual-loop architecture is developed to create coupled energy-transport and dissipation pathways. Combined with Co/Fe3O4 dual-magnetic composites and neural-network-assisted genetic optimization, the absorber achieves continuous ultrabroadband attenuation from 2 to 40 GHz with a thickness of 11 mm. Reference comparisons with planar slab, single-loop, and pyramid structures show that the dual-loop topology provides complete band coverage and a finite-band structural utilization score of 82%. When applied to missile-scale curved surfaces, the absorber reduces the equivalent radar cross section to 1% of the metallic counterpart. This work establishes a practical topology-centered evaluation and design route for ultrabroadband, conformal electromagnetic stealth structures.