Frequency-selective MEMS for miniaturized low-power communication devices

With Q's in the tens to hundreds of thousands, micromachined vibrating reso nators are proposed as integrated-circuit-compatible tanks for use in the l ow phase-noise oscillators and highly selective filters of communications s ubsystems. To date, LF oscillators have been fully integrated using merged CMOS/microstructure technologies, and bandpass filters consisting of spring -coupled micromechanical resonators have been demonstrated in a frequency r ange from HF to VHF. In particular, two-resonator micromechanical bandpass filters have been demonstrated with frequencies up to 35 MHz, percent bandw idths on the order of 0.2%, and insertion losses less than 2 dB, sigher ord er three-resonator filters with frequencies near 455 kHz have also been ach ieved, with equally impressive insertion losses for 0.09 % bandwidths, and with more than 64 dB of passband rejection. Additionally, free-free-beam si ngle-pole resonators have recently been realized with frequencies up to 92 MHz and Q's around 8000. Evidence suggests that the ultimate frequency rang e of this high-Q tank technology depends upon material limitations, as well as design constraints, in particular, to the degree of electromechanical c oupling achievable in microscale resonators.