A highly feasible approach to achieve a broadband radar cross section (RCS) reduction using a simple magnetic metasurface is presented. A magnetic absorbing material (MAM) with high permittivity and magnetic loss is introduced into the metasurface design instead of the more common dielectric material to considerably reduce its thickness. The metasurface is composed of an optimized two-dimensional array of MAM meta-atoms and a metal plate in back. The meta-atoms share a simple square ring shape but with variable geometrical parameters, forming strong absorption in different frequency bands with large reflection phase differences. By hybridizing the absorption and phase-cancelation technique, a 10-dB RCS reduction from 3.4 to 18 GHz is achieved at a thickness of only 4 mm. Further experimental measurements are provided to evaluate the performance. Our work provides a promising way to broaden the bandwidth of RCS reduction with low density, reduced thickness, and stable performance, which can be utilized in harsh physical and chemical environments.
This paper presents a high-temperature-resistant frequency selective metasurface with wide-band low-backward scattering at lower frequencies and wide-band efficient transmission at higher frequencies. According to functions, it consists of three functional layers: a lagging made of low-loss insulation tile, a diffusive metasurface, and a frequency selective surface. The diffusion metasurface is comprised of special arranged various square rings, where meander lines are integrated ensuring transmission at higher frequencies. Separated by a piece of honeycomb paper, a triple-layer coupled-resonator spatial filter frequency selective surface is placed below the diffusive metasurface. Based on the phase cancellation technique and dual-resonance transmission, 10 dB reduction of radar cross-section (RCS) is achieved from 2.45 GHz to 11.55 GHz, and a wide-band transmission lower than 1 dB is obtained in 17.33–19.08 GHz. In addition, a standard thermal test and subsequent electromagnetic test show that our sample maintains good performance after being heated at 500 ℃ for 5 s. This work opens a new route of designing frequency-selective metasurfaces with high-temperature resistance.
We study the edge modes of a finite LC-resonator circuit that consists of alternatingly arranged inductors, separated by identical capacitors, each of which is grounded. The circuit has the configuration of the Su-Schrieffer-Heeger (SSH) model, and one-to-one correspondence between these two models can be established. Interestingly, when the corresponding SSH model is in the topological nontrivial regime, only one topological edge mode appears in the finite LC-resonator circuit, and the other is absent. Through the analysis of the circuit Hamiltonian, we find that only by reducing the boundary capacitance can the missing topological edge mode occur, but the reappeared topological mode is different from the standard one. When the boundary capacitance is lower than a critical value, a Tamm mode related to the local resonance also appears. When the finite circuit system is in the trivial regime, the replacement of the boundary capacitor could result in only the Tamm mode due to the restriction of the bulk-edge correspondence. The present study of the influence of the boundary configuration on the topological edge modes will deepen our understanding of topolectrical circuits.
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