Piezoelectric resonator filter

A piezoelectric resonator filter for allowing a high-frequency signal in a desired frequency band to pass therethrough, comprising three or more reactance elements in serial connection between an input terminal and an output terminal and at least four or more piezoelectric resonators in parallel connection between the input terminal and the output terminal, the three or more reactance elements and the four or more piezoelectric resonators being disposed in a ladder connection, wherein,

• among the four or more piezoelectric resonators, at least two non-adjoining piezoelectric resonators are included in a first filter group,
• among the piezoelectric resonators not included in the first filter group, at least two non-adjoining piezoelectric resonators are included in a second filter group,
• the at least two non-adjoining piezoelectric resonators in the first filter group share a common electrode which is grounded via a first inductor component, the common electrode being opposite to electrodes which are connected to the three or more reactance elements, and
• the at least two non-adjoining piezoelectric resonators in the second filter group share a common electrode which is grounded via a second inductor component, the common electrode being opposite to electrodes which are connected to the three or more reactance elements.

A duplexer comprising:

• a transmission filter for allowing a signal in a transmission band to pass therethrough and attenuating a signal in a reception band;
• and
• a reception filter for allowing a signal in the reception band to pass therethrough and attenuating a signal in the transmission band,
• wherein the transmission filter and/or the reception filter is:
• a piezoelectric resonator filter for allowing a high-frequency signal in a desired frequency band to pass therethrough, including two or more reactance elements in serial connection between an input terminal and an output terminal and at least three or more piezoelectric resonators in parallel connection between the input terminal and the output terminal, the two or more reactance elements and the three or more piezoelectric resonators being disposed in a ladder connection, wherein,
• at least two non-adjoining piezoelectric resonators among the three or more piezoelectric resonators share a common electrode, the common electrode being opposite to electrodes which are connected to the two or more reactance elements, and
• the shared common electrode is grounded via an inductor component.

A duplexer comprising:

• a transmission filter for allowing a signal in a transmission band to pass therethrough and attenuating a signal in a reception band;
• and
• a reception filter for allowing a signal in the reception band to pass therethrough and attenuating a signal in the transmission band,
• wherein the transmission filter and/or the reception filter is:
• a piezoelectric resonator filter for allowing a high-frequency signal in a desired frequency band to pass therethrough, including three or more reactance elements in serial connection between an input terminal and an output terminal and at least four or more piezoelectric resonators in parallel connection between the input terminal and the output terminal, the three or more reactance elements and the four or more piezoelectric resonators being disposed in a ladder connection, wherein,
• among the four or more piezoelectric resonators, at least two non-adjoining piezoelectric resonators are included in a first filter group,
• among the piezoelectric resonators not included in the first filter group, at least two non-adjoining piezoelectric resonators are included in a second filter group,
• the at least two non-adjoining piezoelectric resonators in the first filter group share a common electrode which is grounded via a first inductor component, the common electrode being opposite to electrodes which are connected to the three or more reactance elements, and
• the at least two non-adjoining piezoelectric resonators in the second filter group share a common electrode which is grounded via a second inductor component, the common electrode being opposite to electrodes which are connected to the three or more reactance elements.

A duplexer comprising:

• a transmission filter for allowing a signal in a transmission band to pass therethrough and attenuating a signal in a reception band;
• and
• a reception filter for allowing a signal in the reception band to pass therethrough and attenuating a signal in the transmission band,
• wherein the transmission filter and/or the reception filter is:
• a piezoelectric resonator filter for allowing a high-frequency signal in a desired frequency band to pass therethrough, including three or more reactance elements in serial connection between an input terminal and an output terminal and at least four or more piezoelectric resonators in parallel connection between the input terminal and the output terminal, the three or more reactance elements and the four or more piezoelectric resonators being disposed in a ladder connection, wherein,
• among the four or more piezoelectric resonators, at least two non-adjoining piezoelectric resonators are included in a filter group,
• the at least two non-adjoining piezoelectric resonators in the filter group share a common electrode which is connected to a first inductor component, the common electrode being opposite to electrodes which are connected to the three or more reactance elements, and
• the first inductor component and at least one piezoelectric resonator not included in the filter group are grounded via a second inductor component.

A communication device comprising a filter, wherein the filter is:

• a piezoelectric resonator filter for allowing a high-frequency signal in a desired frequency band to pass therethrough, including three or more reactance elements in serial connection between an input terminal and an output terminal and at least four or more piezoelectric resonators in parallel connection between the input terminal and the output terminal, the three or more reactance elements and the four or more piezoelectric resonators being disposed in a ladder connection, wherein,
• among the four or more piezoelectric resonators, at least two non-adjoining piezoelectric resonators are included in a first filter group,
• among the piezoelectric resonators not included in the first filter group, at least two non-adjoining piezoelectric resonators are included in a second filter group,
• the at least two non-adjoining piezoelectric resonators in the first filter group share a common electrode which is grounded via a first inductor component, the common electrode being opposite to electrodes which are connected to the three or more reactance elements, and
• the at least two non-adjoining piezoelectric resonators in the second filter group share a common electrode which is grounded via a second inductor component, the common electrode being opposite to electrodes which are connected to the three or more reactance elements.

A communication device comprising a filter, wherein the filter is:

• a piezoelectric resonator filter for allowing a high-frequency signal in a desired frequency band to pass therethrough, including three or more reactance elements in serial connection between an input terminal and an output terminal and at least four or more piezoelectric resonators in parallel connection between the input terminal and the output terminal, the three or more reactance elements and the four or more piezoelectric resonators being disposed in a ladder connection, wherein,
• among the four or more piezoelectric resonators, at least two non-adjoining piezoelectric resonators are included in a filter group,
• the at least two non-adjoining piezoelectric resonators in the filter group share a common electrode which is connected to a first inductor component, the common electrode being opposite to electrodes which are connected to the three or more reactance elements, and
• the first inductor component and at least one piezoelectric resonator not included in the filter group are grounded via a second inductor component.