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https://research.monash.edu/en/publications/transmitting-high-power-rf-acoustic-radiation-via-fluid-couplants/ Transmitting high power rf acoustic radiation via fluid couplants into superstrates for... high power https://www.img.ufl.edu/publication/2305/3d-integrated-high-gain-rectenna-package-metamaterial-superstrates-high-efficiency 3D integrated high gain rectenna in package with metamaterial superstrates for high efficiency... high gain