Elastic wave devices

Abstract

The objective is to provide an elastic wave device that improves the steepness of the low-frequency end of the passband in the passband characteristics. [Solution] An elastic wave device 10 having a passband comprises a plurality of series resonant circuits 101, 102, 103, 104 connected in series, and a plurality of parallel resonant circuits 111, 112, 113 connected between the series resonant circuits and ground. The plurality of series resonant circuits and parallel resonant circuits include a piezoelectric substrate and resonators S1, S2, S3, S4, P1, P2, P3 having IDT electrodes formed on the piezoelectric substrate. At least one of the plurality of series resonant circuits has a capacitive element C3 connected in parallel with the resonator of the series resonant circuit, and the resonant frequency is lower than the passband frequency, and the anti-resonant frequency is lower than the passband frequency, comprising a low-frequency side resonant circuit.

Claims

1. A passband elastic wave device, Multiple series resonant circuits connected in series, A plurality of parallel resonant circuits are connected between the series resonant circuit and ground, Equipped with, The plurality of series resonant circuits and the parallel resonant circuits include a piezoelectric substrate and a resonator having an IDT electrode formed on the piezoelectric substrate. At least one of the plurality of series resonant circuits has a capacitive element connected in parallel with the resonator of the series resonant circuit, and is a low-frequency side resonant circuit whose resonant frequency is lower than the passband frequency and whose anti-resonant frequency is lower than the passband frequency. Elastic wave device.

2. The anti-resonant frequency of the low-frequency side resonant circuit is higher than the resonant frequencies of all of the parallel resonant circuits combined. The elastic wave device according to claim 1.

3. The resonant frequency of the low-frequency side resonant circuit is higher than the resonant frequencies of all the parallel resonant circuits combined. The elastic wave device according to claim 2.

4. The capacitance of the capacitive element in the low-frequency resonant circuit is greater than the capacitance of the resonator in the low-frequency resonant circuit. The elastic wave device according to claim 1.

5. The low-frequency side resonant circuit comprises a divided resonator formed by connecting multiple resonators in series, and a capacitive element connected in parallel to the multiple divided resonators connected in series. The elastic wave device according to claim 1.

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