Coustic filter and resonator on periodical poled LiTaO₃

A periodical poled (PP) plate looks like a cross-field model of an interdigital transducer (IDT) by Smith. Therefore, a top-electrode/PP-plate/ bottom-electrode has a possibility to generate an acoustic wave. Though acoustic wave devices using a PP plate and a pp film on substrate have been reported, their frequency responses were very weak as 0.1 to 3dB. It is considered that because their PP devices have neither electrode fingers of IDTs nor grating electrode reflectors, they do not have any effective reflection to realize a good frequency response, while conventional SAW devices have them. This time, authors have proposed an effective reflector using an edge reflection for the PP substrate device and applied it to a resonator and a resonator filter on a PP Z-plane LiTaO₃ plate, which is different from previously reported substrates. As the result, authors have realized the resonator and the resonator filter having good frequency characteristics such as an impedance ratio of 34 dB, and an insertion loss of 2.6 dB and a relative bandwidth of 2.2 %, respectively, for the first time.