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Metamaterials are highly demanded for advanced applications in absorbers, sensors, and filters. However, metamaterial reflectors, especially broadband reflectors, remain challenging. In this paper, we theoretically investigate a wideband metamaterial reflector which consists of cross shaped graphene strips and a silica (SiO2) substrate. The cross shaped graphene strips are coated on the top of the structure, and the cross shape rotated 45° graphene strips are spun on the bottom of it. The calculated reflection can be tuned through length and width of the graphene strips. By comparison, not only broadband reflection but also analogue electromagnetically induced reflection (EIR) can be realized. Moreover, the structure can generate a bi-directional broadband reflection of insensitive polarization. This kind of bi-directional reflector at microwave frequencies is obtained because the top and bottom graphene strip structures are similar. We employ the electric field distribution of the designed structure to elucidate the mechanism of the analogue EIR effect. We further discuss the influence of incident angle on the analogue EIR effect. Such a bi-directional reflector can be potentially applied to a wideband reflector, antenna, and sensor.

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A high-speed gate driver circuit which can meet both GaN FET and SiC MOSFET is presented. High-speed output drive circuit with wide output drive voltage is introduced in the driver circuit to improve speed and efficiency. By using high-speed level shift circuit and floating step-down low dropout regulator (LDO) circuit, the signal amplitude of the internal circuit for the output drive circuit is reduced, and the speed is greatly improved. Based on the proposed output drive circuit, a galvanically isolated 20 MHz 4 A gate driver using capacitive coupling with 5.5 V to 24 V output drive voltage is design and implemented in 180 nm BCD process. Test results show the prototype gate driver achieves the rise and fall time of 2.2 ns and 2.5 ns respectively under 5.5 V supply for GaN FET driving, and the rise and fall time of 4.1 ns and 4.6 ns respectively under 24 V supply for SiC MOSFET driving with 20 MHz frequency.