Miniaturized multi-band polarization-insensitive microwave absorber using microstrip interdigital capacitor

Abstract

A simple approach for designing a miniaturized multi-band metamaterial absorber using a single meta-pattern is presented at microwave frequencies. The proposed absorber unit cell consists of a set of microstrip interdigital capacitor (IDC) structures strategically configured as a single resonator on a metal-backed dielectric substrate. The geometrical parameters of the unit cell are optimized in such a way that the proposed absorber exhibits quadruple absorption peaks at 2, 3.05, 4.41, and 6.48 GHz with absorption rates of 90.10, 97.90, 93.38, and 95.99%, respectively. The absorption performance was investigated under different polarization angles as well as oblique incidence for both transverse-electric (TE) and transverse-magnetic (TM) polarized waves. The absorber structure has an ultra-thin electrical thickness of 0.010λo with miniaturized periodic unit cell dimensions of 0.1167λo × 0.1167λo (with respect to lowest absorption peak frequency), occupies a compact physical area of only 17.5 mm × 17.5 mm. The absorption mechanism was investigated using surface current and electric field distributions. The proposed absorber was fabricated and its performance was experimentally verified for normal incidence. The results of this study make the proposed absorber suitable candidate for potential applications in detection, sensing, and stealth technologies operating in S and C microwave bands. Most importantly, the design approach has the potential to expand into other frequency regimes for relevant applications via appropriate design scaling.