A broadband metamaterial wave absorber based on carbonyl iron powder modified dielectric layer

Abstract

In the field of broadband metamaterial absorbers, most research efforts have focused on optimizing the resonant layers and designing multi-layer structures, but relatively little attention has been paid to the dielectric layers themselves. This paper proposed a method using carbonyl iron powder to modify the dielectric layer. This method significantly enhances the electromagnetic wave attenuation capability of the dielectric layer with the X-band range for metamaterial absorbers. A broadband absorber with a reflection loss (RL) of less than –10 dB within the frequency range of 4.98–18 GHz and covering the C, X, and Ku band was designed. This work analyzed the surface current distribution and the power loss distribution to elucidate the absorption mechanism of the absorber. It was found that the modified dielectric layer accounted for more than 30% of the total loss in the 2–18 GHz frequency band, and the effective absorption bandwidth (RL ≤ –10 dB) was almost twice that of the unmodified dielectric layer. This enhancement in absorption bandwidth is attributed to the introduction of a new electromagnetic wave loss mechanism by carbonyl iron powder. Meanwhile, the absorber exhibited good angular stability, maintaining at least 80% absorption (RL ≤ –7 dB) in the 7.0–18.0 GHz range even when the incident angle was increased to 60°. The experimental results showed that the measured results matched the simulation results well. Furthermore, compared with other methods for broadening the absorption bandwidth, the metamaterial absorber obtained by this method offers several advantages, including wideband absorption, thin profile, and a simple manufacturing process. This approach provides a new and promising direction for the design of broadband absorbers.

1. Introduction

With the advancement of information technology, the electromagnetic environment has become increasingly intricate. In this context, the use of electromagnetic wave absorbing materials is crucial in both military and civilian sectors [1–2]. Absorbing materials can efficiently absorb and dissipate the energy of incident electromagnetic waves, thereby reducing or eliminating the reflection and transmission of electromagnetic waves [3]. This characteristic makes the wave absorbing materials widely applicable in military equipment, as well as in fields such as telecommunications [4–5], radar [6–9], wireless communication [10–11], stealth technology [12–14], and other fields.

Metamaterials [15], which are artificial material with special structures and properties, have demonstrated significant potential in the field of electromagnetic wave absorption due to their strong designability and ease of adjustment. However, challenges remain in achieving broadband absorption with metamaterials. The combination of metamaterials with traditional absorbing materials is an important approach to broaden the effective absorbing bandwidth of metamaterials [16–17]. For example, Shou et al. [18] designed an ultrathin S-band metamaterial absorber with a total thickness of 3.4 mm. The structure incorporated a magnetic top layer and a metamaterial pattern at the middle layer, achieving >90% absorption from 1.73 to 4.04 GHz. This exemplifies how hybrid designs enhance bandwidth performance. Yang et al. [19] proposed a wideband thin microwave absorbing comprising a metal-based planar metamaterial sandwiched between two lamellar carbonyl iron layers, achieving a reflection loss below –9.3 dB in the range of 3.6–18.0 GHz. Yang et al. [20] proposed a design and simulation of a composite absorber based on metamaterials and magnetic materials, with a total thickness of 4.5 mm, achieving radar cross section (RCS) reduction of 8.5 dB in the range from 300 MHz to 2 GHz and with the maximum RCS reduction of 13 dB. Lei et al. [21] has proposed a thin and light magnetic metamaterial absorber with a strong absorption performance of 23.63 dB and an effective absorption bandwidth of 2.46 GHz at a thickness of 0.9 mm. Two-dimensional Ti3CNTx-based magnetic composites have been successfully fabricated by Ma et al. [22] using the method of electrostatic self-assembly. At a thickness of 4.5 mm, an absorption bandwidth of 12.5 GHz was achieved by varying the loading of Ti3CNTx in the composite and the filling rate of the composite in the absorber, covering the frequency ranging from 5.5 to 18 GHz. Jaiswar et al. [23] proposes an ultra-wideband microwave absorber that combines a frequency-selective surface with a dielectric layer.