Filter and multiplexer
AssigneeMurata Manufacturing Co., Ltd.
InventorMasanori Kato
Life of this patent
Estimating the term…
Abstract
A filter having a pass band includes a series circuit in which a series arm resonator and a first inductor are connected in series with each other and which forms at least part of a signal path R connecting a first input/output terminal and a second input/output terminal and a parallel arm resonator connected between one end of the series circuit and a ground. The series circuit becomes inductive in the pass band. An anti-resonant frequency of the series arm resonator is higher than a frequency at a higher-frequency end of the pass band. A resonant frequency of the parallel arm resonator is higher than the anti-resonant frequency of the series arm resonator.
Claims11
A filter having a pass band, the filter comprising:
- a series circuit in which a series arm resonator and a first inductor are connected in series with each other and which forms at least part of a signal path connecting a first input/output terminal and a second input/output terminal;
- a parallel arm resonator connected between one end of the series circuit and a ground;
- a second inductor connected to at least one of a first portion between the series circuit and the first input/output terminal on the signal path or a second portion between the series circuit and the second input/output terminal on the signal path;
- and
- a capacitor connected in parallel to the second inductor,
- wherein the series circuit becomes inductive in the pass band,
- wherein an anti-resonant frequency of the series circuit is higher than a frequency at a higher-frequency end of the pass band, and
- wherein a resonant frequency of the parallel arm resonator is higher than the anti-resonant frequency of the series circuit.
A multiplexer comprising:
- a first filter formed of a first LC resonant circuit and an elastic wave resonator, the first filter having a pass band of approximately 2300 MHz to approximately 2690 MHz;
- a second filter comprising:
- a series circuit in which a series arm resonator and a first inductor are connected in series with each other and which forms at least part of a signal path connecting a first input/output terminal and a second input/output terminal;
- a second inductor connected to at least one of a first portion between the series circuit and the first input/output terminal on the signal path or a second portion between the series circuit and the second input/output terminal on the signal path;
- a capacitor connected in parallel to the second inductor;
- and
- a parallel arm resonator connected between one end of the series circuit and a ground,
- wherein an anti-resonant frequency of the series circuit is higher than a frequency at a higher-frequency end of the pass band,
- wherein a resonant frequency of the parallel arm resonator is higher than the anti-resonant frequency of the series circuit;
- and
- a third filter formed of a second LC resonant circuit and having a pass band of approximately 617 MHz to approximately 960 MHz,
- wherein one end of the first filter, one end of the second filter, and one end of the third filter are connected to each other.
A filter having a pass band, the filter comprising:
- a series circuit in which a first inductor and a second inductor are connected in a series arm which forms at least part of a signal path connecting a first input/output terminal and a second input/output terminal;
- a parallel arm resonator connected between one end of the series circuit and a ground;
- and
- a third inductor connected to at least one of a first portion between the series circuit and the first input/output terminal on the signal path or a second portion between the series circuit and the second input/output terminal on the signal path,
- wherein the series circuit becomes inductive in the pass band,
- wherein an anti-resonant frequency of the series circuit is higher than a frequency at a higher-frequency end of the pass band, and
- wherein a resonant frequency of the parallel arm resonator is higher than the anti-resonant frequency of the series circuit, and
- wherein a Q value of the first inductor and the second inductor is larger than a Q value of the third inductor in the pass band.
Dependencies are inferred from the claim text.