Inhomogeneous substrate metamaterial absorbers with broadband absorption spanning low and high frequency bands

Abstract

It is a significant and challenging work to develop broadband microwave absorption spanning low and high frequencies. The efficient combination of conventional microwave absorbers (CMAs) and emerging metamaterial absorbers (MMAs) would be a viable solution, but this has not yet been successful. This paper reveals a redundant and substitutable part in the substrate of an MMA by analyzing its field distribution, and hereby proposes an inhomogeneous substrate metamaterial absorber (ISMA) by substituting the redundant substrate part with a CMA. The ISMA integrates the strong absorption of the MMA at low frequency with the broadband absorption of the CMA at high frequency. An inhomogeneous substrate-based circuit model, where the circuit elements are in close correlation with the unit cell structures and the constitutive parameters of different substrate regions, has been established to derive and confirm the design strategy of ISMAs. As an example, a 2 mm thick ISMA is designed, simulated and measured to demonstrate perfect integration of the strong resonance absorption near 2.45 GHz of the MMA and the broadband absorption at 8–18 GHz of the CMA. The concept and design method of ISMAs paves the way for MMAs to achieve distinct absorption performances, such as broadband absorption spanning low and high frequencies, by manipulating their substrate.