A Highly Selective Rasorber Based on Second-Order Resonance

A novel frequency-selective rasorber with one highly selective passband between two absorption bands is presented. Based on the equivalent circuit analysis, the approach of using a second-order band-pass response in the lossless layer is adopted to improve the selectivity of the passband. A two-layered structure consisting of one lossy and one lossless layer is then used for implementation. The lossy layer is constructed using stub resonators, while an aperture-coupled resonator is used to realize lossless layer and achieve the highly selective passband. Under normal incidence, the operating bandwidth of the proposed rasorber is 110.6%. One passband with sharp roll-off edge and small insertion loss (0.08 dB) is achieved at 4.3 GHz. For demonstration, one prototype was fabricated and measured, and a good agreement is observed accordingly.