A protocol for automated passband correction of high-order microelectromechanical filters

A systematic protocol for filter passband correction, together with voltage-controlled frequency tuning provided by capacitive-gap transducers, has made possible a 4-resonator micromechanical filter with a 0.1% bandwidth commensurate with the needs of channel-selection and an impressive 20-dB shape factor of 1.59. Indeed, a filter with this small a percent bandwidth would yield very poorly without this tuning mechanism and correction protocol, since typical finite fabrication mismatch tolerances on the order of 300ppm do not permit an undistorted filter passband without post-fabrication tuning. Although demonstrated at a medium frequency (MF) of only 523.5 kHz, this filter passband correction protocol is directly applicable to higher frequency small percent bandwidth filters targeted for ultra-low power RF channel-selecting communication front-ends. An automated computer-controllable passband tuning protocol like that demonstrated here is among the more important ingredients needed to realize an RF channel-selecting filter bank.