Stacked crystal filters implemented with thin films

Low-insertion-loss 1-GHz stacked crystal filters have been implemented with thin films of piezoelectric AlN. Two-pole filters having insertion losses of less than 2 dB have been fabricated on Si and GaAs substrates using microelectronic processing techniques. These devices can serve as high-performance front-end filters for receivers or for other frequency-control applications. The over-moded stacked crystal shows considerable promise as a two-port 50 Ω high-Q feedback element for oscillators or for other narrowband applications