THIN FILM RESONATOR BASED LOW INSERTION LOSS FILTERS.

Bulk acoustic wave resonators using thin piezoelectric films of aluminum nitride and zinc oxide fabricated on Si, GaAs, and other substrates were investigated. Bandpass filters implemented using thin-film bulk-acoustic wave resonators (TFR) are examined. Three basic forms of TFR-based multipole filters are addressed that were synthesized for an integrated received front end for the global positioning satellite (GPS) system. These are the monolithic crystal filter (MCF), the ladder filter, and the stacked crystal filter (SCF). The resonators use C-axis vertical piezoelectric material to support longitudinal-mode wave propagation. Low insertion loss filters were demonstrated in the 1 to 2 GHz range for GPS applications. Performance characteristics of these filters are presented along with a brief discussion of the progress made in deriving filters from the piezoelectric TFR technology.