Electrostatically controlled variable capacitor
Goodwin, S. (2002). IPC No. U.S.Electrostatically controlled variable capacitor (Patent No. 6373682.)
A MEMS (Micro Electro Mechanical System) electrostatically operated high voltage variable controlled capacitor device is provided. This device can store high energy over a wide range while using relatively low electrostatic operating voltages. The MEMS device comprises a microelectronic substrate, a substrate signal electrode, and one or more substrate control electrodes. The MEMS device also includes a moveable composite overlying the substrate, having a composite signal electrode, one or more composite control electrodes, and a biasing element. In cross-section, the moveable composite comprises at least one electrode layer and, in most instances, a biasing layer. In length, the moveable composite comprises a fixed portion attached to the underlying substrate and a distal portion moveable with respect to the substrate electrode. The distal and/or medial portions of the moveable composite are biased in position when no electrostatic force is applied. Additionally, the MEMS device comprises insulators to electrically isolate the substrate and electrodes. Applying a variable controlled voltage between the substrate control electrode and moveable composite control electrode, controls the bias of the moveable composite and, in turn, controls the capacitance between the substrate signal electrode and the composite signal electrode. Various embodiments further define the various layering alternatives if the moveable composite, shaping of the electrodes and placement of the electrodes. Additionally, a system for electrostatically controlled variable capacitance comprises a variable controlled voltage source coupled to the control electrodes of the MEMS device of the present invention and a circuit signal electrically coupled to the signal electrodes of the MEMS device. A method of using and a method for making the aforementioned electrostatic MEMS device are also provided.