US Patent 11657980 Dielectric fluid variable capacitor

A variable capacitor includes an enclosure having first and second conductive collars separated by an intermediate electrically insulating element. A movable capacitor plate assembly is electrically coupled to the first conductive collar, and a fixed capacitor plate assembly is electrically coupled to the second conductive collar. An actuator extends into the enclosure for advancing and retracting the movable capacitor plate assembly relative to the fixed capacitor plate assembly. A hermetically sealed volume within the enclosure contains a dielectric fluid serving as a dielectric between a capacitor plate of the movable capacitor plate assembly and a capacitor plate of the fixed capacitor plate assembly. A flexible structure is provided to contain the dielectric fluid displaced when the movable capacitor plate assembly is advanced toward the fixed capacitor plate assembly.