Miniaturized Wide-Angle Rasorber With a Wide Interabsorption High Transparent Bandpass Based on Multiple 2.5-D Resonators

A miniaturized high selectivityfrequency selective rasorber (FSR) with a wide interabsorption 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 interdigitated 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 the 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 is proposed to analyze its operating principle. The dimensions of the miniaturized element are 0.12 lambda(L) x 0.12 lambda(L) x 0.118 lambda(L). While maintaining a 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 degrees). A prototype of miniaturized FSR has been manufactured and measured, showing a reasonable agreement with simulations.