Miniaturized wide-angle rasorber with a wide inter-absorption high transparent bandpass based on multiple 2.5-D resonators

A miniaturized high selectivity Frequency Selective Rasorber (FSR) with a wide inter-absorption high transparent bandpass based on multiple 2.5-Dimensional (2.5-D) resonators is investigated. The main contribution is the achievement of a wide and high transparent passband by combining the large inductance of Parallel Resonators (PRs) and cascading two 2.5-D PRs, which also provide the function of miniaturization. The 2.5- D PR is implemented by connecting the interdigited capacitor and the metal meandered strip-line on both surfaces of a lossy layer through metalized vias. The inductor and capacitor values of 2.5-D PR can be individually adjusted to shift passband’s central frequency. The lossy element is realized by inserting two 2.5-D strip-type PRs at the center of each side of a meandered cross-dipole loaded with two resistive sheets on both sides. An Equivalent Circuit Model (ECM) is proposed to analyze its operating principle. The dimensions of the miniaturized element are 0.12λL×0.12λL×0.118λL. While maintaining good wide passband (-1dB relative bandwidth is 21.2%), the miniaturized FSR satisfies the characteristic of polarization insensitivity (TE and TM) and angular insensitivity (up to 45°). A prototype of miniaturized FSR has been manufactured and measured, showing a reasonable agreement with simulations.