Design of Frequency-Tunable Metagrating by Loading Varactor Diodes

When the unit period length of the metasurface is increased from the original far less than the wavelength to once the wavelength, the electromagnetic(EM) response of the metasurface will be transformed into grating diffraction, and multi-order diffraction modes will be generated. At this time, we can realize the control of EM wave front and so on by adjusting different modes. In this paper, we use a bowtie-like pattern metagrating structure, according to Floquet-Bloch (FB) modes and grating equation, to realize the function of efficient retroreflection at a certain frequency. In addition, the mechanism of the multi-order diffraction modes is explored by equivalent circuit analysis method. Therefore, we load varactor diodes in the metagrating cell structure to make the retroreflection frequency adjustable between 3.58GHz and 4.25GHz, and the retroreflection efficiency is totally more than 70%.