Toyo Communication Equipment Co., Ltd.

Kiyoshi Nakamura

Siward Technology Co., Ltd

Koichi Hirama

Masashi Iwata

Hiroshi Hasegawa

Takumi Ozaki

[PROBLEM TO BE SOLVED] To provide a bulk wave resonator having a high frequency passband. [SOLUTION] A bulk wave resonator using a bulk wave, includes a support substrate, an acoustic multilayer film that includes, stacked on the support substrate, a plurality of types of dielectrics having different acoustic impedances, a piezoelectric layer that is stacked on the acoustic multilayer film, a first electrode, and a second electrode. The first and second electrodes are disposed to face each other with a gap therebetween on a first surface of the piezoelectric layer opposite to the acoustic multilayer film, and are applied with a voltage for allowing the piezoelectric layer to generate the bulk wave. A direction that is parallel to the surface of the piezoelectric layer and in which the first electrode and the second electrode face each other is defined as a first direction. The bulk wave resonator uses, as a main mode, a bulk wave in the first direction that is generated by a thickness shear vibration in the first direction, which is excited by a parallel electric field formed in the piezoelectric layer when a voltage applied to the first electrode and the second electrode.

Bulk wave resonator and bandpass filter

A unit for suppressing harmonic vibration of a lower order which does not have desired frequency in an overtone resonator consisting main electrodes and sub electrodes. Harmonic vibration of a lower order suppressing piezoelectric vibrator comprises main electrodes arranged on a piezoelectric substrate and sub electrodes arranged in the vicinity of the main electrodes with gaps provided therebetween. If the electric equivalent circuit of the resonator is expressed by a coupling circuit which connects in series a circuit, which connects in parallel a series resonance circuit by the sub electrodes and coupling capacity indicating that the main electrodes are coupled with the sub electrodes, to a series resonance circuit by the main electrodes, then their loop frequencies substantially coincide with each other.

Growing community of inventors

Sendai, Japan

Kiyoshi Nakamura