The minimum passive element for controlling the shape and width of the monolithic filter, and the pass band response using a thin film bulk acoustic wave device

摘要

PROBLEM TO BE SOLVED: To provide a multipolar type bulk elastic wave resonator stack type crystal filter (multipolar BAWR-SCF). ;SOLUTION: A device 3 has a BAW resonator (BAW1), stacked type crystal filters(SCF) 6 and 8, an impedance inverse element, including capacitors C12 and C23 and an inductor L₀. Also, four ports P1, P2, O1 and O2 are included. BAW resonators BAW1 and SCF 8 are inserted serially between the ports P1 and O1. The BAW1 has the inductor L₀ connected in parallel and both ends of the L₀, that is, both ends of the BAW1, are grounded by way of the capacitors C12 and C23 respectively. Moreover, a central electrode 20 of the SCF6 and 8 is grounded. The ports P2 and O2 are essentially grounded, and this device, a multipolar type BAWR-SCF circuit 3, is a triode device.;COPYRIGHT: (C)1999,JPO