Band-pass filter and branching filter

Patent metadata

Field	Value
Publication number	US-10263600-B2
Application number	US-201615355443-A
Country	US
Kind code	B2
Filing date	Nov 18, 2016
Priority date	Jan 25, 2016
Publication date	Apr 16, 2019
Grant date	Apr 16, 2019

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 provided in series. 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 provided in series. 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; and
an LC resonant circuit and a resonant circuit section provided in series between the first port and the second port, wherein
the resonant circuit section includes at least one acoustic wave resonator provided in a path leading from the first port to the second port,
the resonant circuit section has a resonant frequency and at least one anti-resonant frequency,
the resonant frequency is within the passband,
the at least one anti-resonant frequency is outside the passband, and
the LC resonant circuit is an LC parallel resonant circuit having a resonant frequency outside the passband.

2. 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; and
an LC resonant circuit and a resonant circuit section provided in series between the first port and the second port, wherein
the resonant circuit section includes at least one acoustic wave resonator provided in a path leading from the first port to the second port,
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, and 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. 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; and
an LC resonant circuit and a resonant circuit section provided in series between the first port and the second port, wherein
the resonant circuit section includes at least one acoustic wave resonator provided in a path leading from the first port to the second port,
the resonant circuit section has a resonant frequency and at least one anti-resonant frequency,
the resonant frequency is within the passband,
the at least one anti-resonant frequency is outside the passband,
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. 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 LC resonant circuit and a first resonant circuit section between the common port and the first signal port, the first LC resonant circuit and the first resonant circuit section being arranged in series in this order from the common-port side,
the first resonant circuit section includes at least one acoustic wave resonator provided in a path leading from the first LC resonant circuit to the first signal port, 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.

7. The branching filter according to claim 6 , wherein the first LC resonant circuit is a first LC parallel resonant circuit having a resonant frequency higher than the first high-band cut-off frequency.

8. The branching filter according to claim 6 , wherein the first resonant circuit section includes two acoustic wave resonators connected in series, as the at least one acoustic wave resonator.

9. 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 LC resonant circuit and a second resonant circuit section between the common port and the second signal port, the second LC resonant circuit and the second resonant circuit section being arranged in series in this order from the common-port side,
the second resonant circuit section includes at least one acoustic wave resonator provided in a path leading from the second LC resonant circuit to the second signal port, 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.

10. The branching filter according to claim 9 , wherein the second LC resonant circuit is a second LC parallel resonant circuit having a resonant frequency lower than the second low-band cut-off frequency.

11. The branching filter according to claim 9 , 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. 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 LC resonant circuit and a first resonant circuit section between the common port an

Assignees

• Tdk Corp

Inventors

• Tsukamoto Kazuhiro
• Suzuki Hiroya

Classifications

• H03H7/1791

  Combined LC in shunt or branch path · CPC title

• H03H9/706

  Duplexers · CPC title

• H03H9/72

  Networks using surface acoustic waves · CPC title

• H03H9/703

  Networks using bulk acoustic wave devices · CPC title

• H03H9/725

  Duplexers · CPC title