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In this work, a pure dielectric metamaterial absorber with broadband and thin thickness is proposed, whose structure is designed as periodic cross hole array. The pure dielectric metamaterial absorber with high permittivity is prepared by ceramic reinforced polymer composites. Compared with ones with low permittivity, the absorber with high permittivity is more sensitive to structural parameters, which means that it is easier to optimize equivalent electromagnetic parameter and achieve wide impedance matching by altering the size or shape of unit cell. The optimized metamaterial absorber exhibits the reflection loss below -10 dB in 7.93~35.76 GHz with a thickness of 3.5 mm, which shows favorable absorption property under the oblique incidence of TE polarization (±45°). Whether it is measured or simulated value, the strongest absorbing peak reaches below -45 dB, which exceeds that of most metamaterial absorber. The distributions of power loss density, electric and magnetic field are proposed to study the origin of their strong absorbing property. Multiple resonance mechanisms are developed to explain the phenomenon, including polarization relaxation of dielectric and edge effect of the cross-hole array. This work overcome the shortcoming of narrow absorbing bandwidth of dielectric. It demonstrates that the pure dielectric metamaterial absorber with high permittivity has great potential in the field of microwave absorption.

In this paper, a high-absorption and dual-transmission-bands rasorber (HADTR) was proposed. Different from the reported designs, a foam layer and a FR4 layer are added as top layers in HADTR to improve its absorption and oblique incidence performance. The unit cell of resistive layer is concentric metallic rings loaded with chip resistors based on absorption enforced design to ensure its dual-transmission-bands at the same time. The unit cell of band-stop frequency selective surface (BS-FSS) is double metallic square loops loaded with chip inductors on both sides of FR4 substrate, which expands its reflection band (|S11|≥ − 1.0 dB) without destroying its dual-transmission-bands effectively. At normal incidence, for TE and TM polarization, the HADTR has a low-frequency passband up to 1.34 GHz (|S21|≥ − 1.5 dB), a high-frequency passband from 16.04 to 18.00 GHz (|S21|≥ − 1.5 dB) and a wide 90% absorption band from 5.01 to 10.56 GHz; and the reflection coefficient below − 10 dB and − 20 dB is in the range of 4.48–11.70 GHz and 5.48–9.96 GHz, respectively. For TE/TM polarization, the 90% absorption of oblique incidence stability is 40° and 30° respectively. Strong association between measurement and simulation results validates the design method and the HADTR.

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