Development of a Wide-Tuning-Range Two-Parallel-Plate Tunable Capacitor for Integrated Wireless Communication Systems

This paper reports on the development of a micromachined parallel-plate tunable capacitor with a wide tuning range. Different from conventional two-parallel-plate tunable capacitors, this tunable capacitor consists of one suspended top plate and two fixed bottom plates. One fixed plate and the top plate form a variable capacitor, while the other one provides necessary electrostatic actuation. Among the fabricated prototype devices, a maximum controllable tuning range of 69.8%@1 MHz has been obtained experimentally, ( ) exceeding the theoretical limit 50% of conventional two-parallel-plate tunable capacitors. ( ) A component quality factor Q of 30@5 GHz and a self-resonant frequency far beyond 5 GHz have been achieved. The fabrication process is compatible with the existing standard ( ) IC integrated circuit technology, which makes it suitable for integrated wireless communication applications. 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 322 329,