Abstract
Conventional metamaterial absorbers eliminate the transmitted electromagnetic wave by attaching the metal plate with the unidirectional absorption performance; these absorbers limit the practical applications to a large extent. In this paper, we present a broadband bi-directional metamaterial absorber by etching chip resistors on the resonators for expanding the bandwidth, and two orthogonal I-shaped structures are pasted on the both sides of the ultra-thin substrate (FR-4) instead of the metal plate for enhancing absorptance of the absorber. Simulated results show that absorptance of the designed absorber is larger than 0.9 in 1.43–2.51 GHz along the forward and backward directions under both TE and TM polarizations. Microwave experiments in the chamber are performed to verify the simulations, and the experimental results exhibit the excellent agreement with the simulations. Additionally, two I-shaped structures are orthogonally pasted on an ultrathin substrate, leading to the impedance-matching of both forward and backward directions, and the absorptance can be tailed dynamically via the middle layer of the substrate. The physics of the absorption are visualized by using a transmission line based on equivalent circuits. We claim that the designed bi-directional metamaterial absorber can be a good candidate for electromagnetic stealth and energy harvesting.
Highlights
Metamaterial perfect absorbers (MPAs)-based energy harvesters can transfer the electric energy to the nodes in a wireless sensor network and eliminate the undesirable EM radiations around electronic equipment
A great deal of effort has been made on the design and implementation of multi-band [22–25] and broadband MPAs [1,2,26–30] via tailing the various of patterns and structures
We propose a broadband bi-directional polarization-insensitive MPA working at 1.43–2.51 GHz to efficiently use electromagnetic energy in the environment
Summary
The tunable/switchable MPAs by loading the varactor or PIN diodes have been achieved by plentiful research achievements [35–39]
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