High-order micromechanical electronic filters

Third-order, micromechanical bandpass filters comprised of three folded-beam resonators coupled by flexural mode springs are demonstrated using an IC-compatible, polysilicon surface-micromachining technology. The use of quarter-wavelength coupling beams attached to resonators at their folding-trusses is shown to suppress passband distortion due to finite-mass nonidealities, which become increasingly important on this micro-scale. A balanced, 300 kHz, prototype, three-resonator micromechanical filter is demonstrated with filter Q=590 and stopband rejection greater than 38 dB.