Broadband Transmission Rasorber With Dual-Broadband Absorption by High-Accuracy Equivalent Admittance Analysis Method With Convergent Solution Conditions

In this article, we propose a new frequency selective rasorber (FSR) design method based on equivalent admittance analysis. The analysis separates the effects of the metal structure and substrate on the frequency response of the FSR by equivalence separation, thus improving the accuracy of the equivalence. Meanwhile, the admittance analysis solves the problem of poor quantitative analysis of transmission condition due to the infinite discontinuity of the impedance curve in the traditional impedance analysis method, thus resulting in the convergence of the solution conditions. Then, wide passband design schemes for lossy and lossless layer have been analyzed in the admittance analysis. Subsequently, a TA FSR and a wide passband AT FSR are designed separately. Finally a broadband transmission FSR with dual-broadband absorption is proposed by sequentially cascading the both, and the cascade FSR is optimized by introducing a supplementary absorption layer to improve the frequency selectivity. The multilayer structure guarantees large operating frequency span and wide absorption bandwidth, and the compact structure facilitates good angular stability. The equivalent circuit model and the surface current distribution explore the physical mechanism. The proposed prototype is fabricated, and the measured results achieve a good agreement with the simulated results. The transmission loss is lower 1.5 dB in 6.5–12.5 GHz (63.15%), and the absorption is 85% in 1.6–4.4 GHz (93.3%) and 15.5–24.4 GHz (44.6%). It is significant for the out-of-band broadband electromagnetic shielding of broadband antennas.