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MEMS-Based UHF Monolithic Crystal Filters for Integrated RF Circuits

We report our work in developing microelectromechanical systems (MEMS)-based Ultra High Frequency (UHF) AT-cut quartz monolithic crystal filters operating between 350 and 400 MHz for integration with Si electronics for highly compact Radio Frequency (RF) front-end electronics. Our narrow bandwidth (0.2%) high Q filters have measured insertion losses of -2 dB with temperature stability of roughly 50 ppm over a temperature range of 10°- 80°C. Wafer-level optical metrology and ion milling techniques have been developed to provide enhanced accuracy of the filter center frequency and resonator parameters for optimized performance and improved yields.