Ultra-miniaturized Narrow-band Metamaterial Absorber for L-band

Abstract

An ultra-miniaturized narrow-band metamaterial absorber for L-band is presented in this paper. The proposed design operates at 1.21 GHz with reflective coefficient of -22.3 dB. The unit cell is miniaturized to $0.02 \lambda_{0}$, where $\lambda_{0}$ is the free-space wavelength at center operating frequency. The miniaturization scheme is by using meander-line and plated vias in absorber. Several parts of the metal ground are dug out to avoid connecting with vias. The structure is polarization insensitive as there are plated vias on two opposite sides only. On the upper surface of the medium, meander-lines extend from the sides with vias toward the center of the cell, and the meander-lines are connected by two short vias and a strip in the medium. To explain the mechanism of the proposed absorber, we present an analysis of the current and electric field distribution at the operating frequency. Further, the unit cell is also simulated under various polarization angles $(\varphi)$ and incident angles $(\theta)$. The results show that the proposed absorber exhibits a good oblique incident angular stability of up to 50 degree, as well as a polarization insensitivity of up to 40 degree. The fractional bandwidth is 1.65% centered at 1.21GHz. The high absorptivity for a narrow-band makes the proposed absorber a useful candidate to defense against strong radiation attacks and electromagnetic interface in various electronic circuits in satellite and radar applications. The ultra-miniaturized elements and 2.5D design make it stable at large incident angles.