Acoustical Behavior of Fully-Printed, BST MIM Varactor Modules in High Power Matching Circuits

This work presents three fully-printed, acoustically optimized metal-insulator-metal (MIM) thick film varactor modules, capable of operating in matching circuits rated with up to 700 W. The varactors are based on a barium strontium titanate (BST) dielectric layer with a thickness of 25µm to 36 µm, which is utilized to adjust the acoustical behavior of the varactor. At room temperature, the varactors show a tunability of 17% to 28% with 220V of biasing voltage and a quality factor of 37 to 62 in unbiased state. In biased state, the quality factor is either increased or decreased, depending on the acoustical adjustment of the varactor. With 700W of input power, one varactor shows a maximum tunability of 7% withstanding 118V and 13.6A of RMS RF voltage and current, respectively, dissipating 67W of RF power.