Frequency Selective Rasorber with Low Insertion Loss and Dual-Band Absorptions Using Planar Slotline Structures

Abstract

This letter proposes a dual-polarized frequency selective rasorber (FSR), which exhibits bandpass filtering response together with absorption performance at both sides of the passband. Although the design concept is modified from a three-dimensional FSR, the proposed FSR is implemented by cross-inserting a few identical printed circuit board pieces etched with planar slotline structures, thus releasing difficulties in fabrication and assembly. The bandpass characteristic is provided by lossless resonators constructed in the slotlines with center-loaded U-type strips, whereas the absorption bands are realized by lossy resonators formed in short-circuited slotlines with lumped resistors. Surface current distributions are illustrated to explain the operation mechanism. A prototype of the designed FSR is fabricated and measured. The measured results show that the minimum insertion loss in the passband is about 0.3 dB, and the absorption bandwidths are ranged from 1.6 to 2.3 GHz and from 3.6 to 4.6 GHz, respectively. To further demonstrate the design concept, another FSR with wider absorption bands is developed by introducing more lossy resonators. Moreover, the proposed FSRs feature stable performance under oblique incident angles.