Micromechanical filters for miniaturized low-power communications

With Q’s in the tens to hundreds of thousands, micromachined vibrating resonators are proposed as IC-compatible tanks for use in the highly selective filters of communications subsystems. To date, bandpass filters consisting of spring-coupled micromechanical resonators have been demonstrated in a frequency range from HF to VHF. In particular, two-resonator micromechanical bandpass filters have been demonstrated with frequencies up to 35 MHz, percent bandwidths on the order of 0.2%, and insertion losses less than 2 dB. In addition, free-free beam, single-pole resonators have recently been realized with frequencies up to 92 MHz and Q’s around 8,000. Evidence suggests that the ultimate frequency range of this high-Q tank technology depends upon material limitations, as well as design constraints—in particular, to the degree of electromechanical coupling achievable in micro-scale resonators.