Wideband and low-profile reflective metasurface with miniaturized dimensions and tunable performances using magnetic dielectric for UHF applications

This paper proposes a broadband, miniaturized, and ultralow-profile reflective metasurface loaded with a magnetic dielectric material for ultrahigh-frequency (UHF) applications. The metasurface has a three-layer heterostructure that consists of a circuit pattern, a hybrid air/magnetic dielectric layer, and a metallic reflective surface. The magnetic dielectric applied in this design has the advantages of relatively high permeability and permittivity with low magnetic and dielectric losses, which significantly enhance the operating bandwidth and reduce the profile of the metasurface. In addition, varactor diodes are introduced in the metasurface circuit design to explore the tunable frequency characteristics. To validate the performance of the metasurface, an optimized metasurface prototype and an UHF bow-tie antenna backed by the metasurface were fabricated and measured. The measured results indicate that the designed metasurface achieves a [−90°, +90°] reflection phase bandwidth of 77.6% (370–840 MHz), with an ultralow profile of 11 mm (∼0.013λ of the lowest frequency) and a miniaturized unit size of 50 mm (∼0.06λ). The metasurface-backed antenna achieves a wide bandwidth of 61.9% (384–728 MHz), and when compared with the antenna backed with a perfect electric conductor (PEC) reflector, its maximum gain increases by more than 9 dB. The introduction of magnetic dielectrics into metasurfaces presents a novel paradigm for high-performance integrated radio frequency systems.