Disk-Array Design for Suppression of Unwanted Modes in Micromechanical Composite-Array Filters

A disk composite-array structure has been demonstrated that places its constituent disks in a triangular pattern around a “ mechanical output” disk, while coupling them with half-wavelength links, in order to accentuate a desired resonant mode while suppressing unwanted modes. Using this mechanical circuit structure, disk array-composite filters with less than 0.2% bandwidth and centered in the 150-600 MHz UHF range have been demonstrated with no spurious modes in a ± 200 MHz range around their radial-mode center frequencies. In addition to resonator arraying, these filters utilize lateral solid dielectric capacitive transducers to further reduce dc-bias voltages to as low as 4V. By replacing transverse resonators with higher frequency, higher Q lateral disks, this work provides a path to better performing communication oscillators and filters based on MEMS technology.