Band-pass filter and branching filter

Patent metadata

Field	Value
Publication number	US-2019199323-A1
Application number	US-201916291569-A
Country	US
Kind code	A1
Filing date	Mar 4, 2019
Priority date	Jan 25, 2016
Publication date	Jun 27, 2019
Grant date	—

Abstract

A branching filter includes a first band-pass filter provided between a common port and a first signal port, and a second band-pass filter provided between the common port and a second signal port. The first band-pass filter includes a first LC resonant circuit and a first resonant circuit section. The first resonant circuit section includes a first acoustic wave resonator. The second band-pass filter includes a second LC resonant circuit and a second resonant circuit section. The second resonant circuit section includes a second acoustic wave resonator and an inductor connected in parallel.

First claim

What is claimed is:

1 . A band-pass filter configured to selectively pass a signal of a frequency within a passband not lower than a low-band cut-off frequency and not higher than a high-band cut-off frequency, comprising:
a first port; a second port; a resonant circuit section provided between the first port and the second port; and an LC resonant circuit connected to the resonant circuit section,
wherein
the resonant circuit section includes at least one acoustic wave resonator,
the resonant circuit section has a resonant frequency and at least one anti-resonant frequency,
the resonant frequency is within the passband, and
the at least one anti-resonant frequency is outside the passband.

2 . The band-pass filter according to claim 1 , wherein the at least one anti-resonant frequency is higher than the high-band cut-off frequency.

3 . The band-pass filter according to claim 2 , wherein the resonant circuit section includes two acoustic wave resonators connected in series, as the at least one acoustic wave resonator.

4 . The band-pass filter according to claim 1 , wherein
the resonant circuit section further includes at least one inductor connected in parallel to the at least one acoustic wave resonator, and the resonant circuit section has an anti-resonant frequency lower than the low-band cut-off frequency and an anti-resonant frequency higher than the high-band cut-off frequency, as the at least one anti-resonant frequency.

5 . The band-pass filter according to claim 4 , wherein the resonant circuit section includes, as the at least one acoustic wave resonator, two acoustic wave resonators connected in series, and as the at least one inductor, two inductors respectively connected in parallel to the two acoustic wave resonators.

6 . The band-pass filter according to claim 1 , wherein the LC resonant circuit has a resonant frequency outside the passband.

7 . A branching filter comprising:
a common port; a first signal port; a second signal port; a first filter provided between the common port and the first signal port, and configured to selectively pass a signal of a frequency within a first passband; and a second filter provided between the common port and the second signal port, and configured to selectively pass a signal of a frequency within a second passband higher than the first passband, wherein the first filter is a first band-pass filter, the first passband is a frequency band that is not lower than a first low-band cut-off frequency and not higher than a first high-band cut-off frequency, the first band-pass filter includes a first resonant circuit section provided between the common port and the first signal port, and a first LC resonant circuit connected to the first resonant circuit section, the first resonant circuit section includes at least one acoustic wave resonator, and the first resonant circuit section has a resonant frequency within the first passband and at least one anti-resonant frequency higher than the first high-band cut-off frequency.

8 . The branching filter according to claim 7 , wherein the first resonant circuit section includes two acoustic wave resonators connected in series, as the at least one acoustic wave resonator.

9 . The branching filter according to claim 7 , wherein the first LC resonant circuit has a resonant frequency higher than the first high-band cut-off frequency.

10 . A branching filter comprising:
a common port; a first signal port; a second signal port; a first filter provided between the common port and the first signal port, and configured to selectively pass a signal of a frequency within a first passband; and a second filter provided between the common port and the second signal port, and configured to selectively pass a signal of a frequency within a second passband higher than the first passband, wherein the second filter is a second band-pass filter, the second passband is a frequency band that is not lower than a second low-band cut-off frequency and not higher than a second high-band cut-off frequency, the second band-pass filter includes a second resonant circuit section provided between the common port and the second signal port, and a second LC resonant circuit connected to the second resonant circuit section, the second resonant circuit section includes at least one acoustic wave resonator, and at least one inductor connected in parallel to the at least one acoustic wave resonator, and the second resonant circuit section has a resonant frequency within the second passband, an anti-resonant frequency lower than the second low-band cut-off frequency, and an anti-resonant frequency higher than the second high-band cut-off frequency.

11 . The branching filter according to claim 10 , wherein the second resonant circuit section includes, as the at least one acoustic wave resonator, two acoustic wave resonators connected in series, and as the at least one inductor, two inductors respectively connected in parallel to the two acoustic wave resonators.

12 . The branching filter according to claim 10 , wherein the second LC resonant circuit has a resonant frequency lower than the second low-band cut-off frequency.

13 . A branching filter comprising:
a common port; a first signal port; a second signal port; a first filter provided between the common port and the first signal port, and configured to selectively pass a signal of a frequency within a first passband; and a second filter provided between the common port and the second signal port, and configured to selectively pass a signal of a frequency within a second passband higher than the first passband, wherein the first filter is a first band-pass filter, the first passband is a frequency band that is not lower than a first low-band cut-off frequency and not higher than a first high-band cut-off frequency, the first band-pass filter includes a first resonant circuit section provided between the common port and the first signal port, and a first LC resonant circuit connected to the first resonant circuit section, the first resonant circuit section includes at least one first acoustic wave resonator, the first resonant circuit section has a resonant frequency within the first passband and at least one anti-resonant frequency higher than the first high-band cut-off frequency, the second filter is a second band-pass filter, the second passband is a frequency band that is not lower than a second low-band cut-off frequency and not higher than a second high-band cut-off frequency, the second band-pass filter includes a second resonant circuit section provided between the common port and the second signal port, and a second LC resonant circuit connected to the second resonant circuit section, the second resonant circuit section includes at least one second acoustic wave resonator, and at least one inductor connected in parallel to the at least one second acoustic wave resonator, and the second resonant circuit section has a resonant frequency within the second passband, an anti-resonant frequency lower than the second low-band cut-off frequency, and an anti-resonant frequency higher than the second high-band cut-off frequency.

14 . The branching filter according to claim 13 , wherein
the first resonant circuit section includes, as the at least one first acoustic wave resonator, two first acoustic wave resonators connected in series, and the second resonant circuit section includes, as the at least one second acoustic wave resonator, two second acoustic wave resonators connected in series, and as the at least one inductor, two inductors r

Assignees

• Tdk Corp

Inventors

• Tsukamoto Kazuhiro
• Suzuki Hiroya

Classifications

• H03H7/1775

  Parallel LC in shunt or branch path (H03H7/1791 takes precedence) · CPC title

• H03H7/1725 Primary

  Element to ground being common to different shunt paths, i.e. Y-structure · CPC title

• H03H9/542 Primary

  including passive elements (H03H9/545 takes precedence) · CPC title

• H03H7/1758

  Series LC in shunt or branch path (H03H7/1791 takes precedence) · CPC title

• H03H9/725

  Duplexers · CPC title