Q-enhancement of microelectromechanical filters via low-velocity spring coupling

A micromechanical filter design technique based on low-velocity coupling of resonators is described that can achieve percent bandwidths less than 0.1% without the need for aggressive, submicron lithography. Using this low-velocity coupling technique, an IC process limited to feature sizes no less than 2 μm was utilized to achieve three-resonator micromechanical filters centered at 340 kHz with percent bandwidths as low as 0.1% (filter Q´s as high as 800), passband rejections up to 60 dB (the highest reported to date on the micro-scale), and insertion losses less than 1 dB. In addition, two-resonator 7.82 MHz filters were demonstrated with percent bandwidths of 0.2% and comparable insertion losses, all within an area of less than 50×50 μm²