Thin-film resonator ladder filter

Thin-film bulk acoustic wave resonator (BAWR) ladder filters have been realized with IL/spl sim/2.2 dB, and selectivity /spl sim/15 dB for a three resonator filter, IL/spl sim/5 dB and selectivity /spl sim/32 dB for a five resonator filter. Filters with seven and nine resonators have also been characterized. This performance corresponds to achieving a figure of merit Q/r/spl sim/10. The performance possibilities of ladder filters have been calculated with the Q/r figure of merit as a parameter. It is anticipated with improvements in processing and device designs, AlN or ZnO thin-film BAWR ladder filters should achieve IL/spl sim/1.5 dB and selectivity /spl sim/40 dB, corresponding to Q/r/spl sim/40 at 1.5 GHz.<
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