Hybrid Rasorber Based on 3-D Bandpass Frequency-Selective Structures

A dual-polarized hybrid frequency selective rasorber with absorption-transmission-absorption frequency response is proposed in this letter. The rasorber has a flat transmission window with low insertion loss within a wide absorption band. A 3-D bandpass structure is designed based on multiple propagating modes to generate a second-order passband and also to act as a reflecting ground for the upper lossy layer. A 2-D resistor-loaded layer of metallic patches is then cascaded with the bottom 3-D structure to absorb undesired reflected waves at two-sided frequencies. Furthermore, the total structural thickness of the rasorber is only around 0.09 wavelengths at the lowest operating frequency, which is a much thinner structure compared with many conventional 3-D frequency selective rasorbers.