Filter circuit, front end circuit, and module

Patent metadata

Field	Value
Publication number	US-10187109-B2
Application number	US-201715434943-A
Country	US
Kind code	B2
Filing date	Feb 16, 2017
Priority date	Mar 14, 2016
Publication date	Jan 22, 2019
Grant date	Jan 22, 2019

Abstract

A filter circuit includes: a variable filter that is connected between a common terminal and a node and configured to change a passband thereof; a receive switch connected between a receive terminal, from which a reception signal in a first band is output, and the node; and a transmit switch connected between a transmit terminal, to which a transmission signal in a second band different from the first band is input, and the node.

First claim

What is claimed is:

1. A filter circuit comprising:
a variable filter that is connected between a common terminal and a node and configured to change at least one of a low-frequency end and a high frequency end of a passband thereof;
a receive switch connected between a receive terminal, from which a reception signal in a first receive band of a first band is output, and the node, said first band being corresponding to an E-UTRA operating band and including a first transmit band and said first receive band, a reception signal in the first receive band being output from the receive terminal; and
a transmit switch connected between a transmit terminal, to which a transmission signal in a second transmit band of a second band is input, and the node, said second band being corresponding to an E-UTRA operating band that is different from the first band and including said second transmit band and a second receive band, and
wherein a difference between a high-frequency end of the first receive band and a high-frequency end of the second transmit band is smaller than a difference between the high-frequency end of the first receive band and a high-frequency end of the first transmit band and a difference between a high-frequency end of the second receive band and the high-frequency end of the second transmit band, and
wherein a difference between a low-frequency end of the first receive band and a low-frequency end of the second transmit band is smaller than a difference between the low-frequency end of the first receive band and a low-frequency end of the first transmit band and a difference between a low-frequency end of the second receive band and the low-frequency end of the second transmit band.

2. The filter circuit according to claim 1 , wherein
when the reception signal in the first receive band is received, the passband of the variable filter is changed to the first receive band of the first band, the receive switch is turned on, and the transmit switch is turned off, and
when the transmission signal in the second transmit band is transmitted, the passband of the variable filter is changed to the second transmit band of the second band, the receive switch is turned off, and the transmit switch is turned on.

3. The filter circuit according to claim 1 , wherein
when the reception signal in the first receive band is received, the transmit switch is turned off and the passband of the variable filter is changed to the first receive band of the first band, and thereafter, the receive switch is turned on, and
when the transmission signal in the second transmit band is transmitted, the receive switch is turned off and the passband of the variable filter is changed to the second transmit band of the second band, and thereafter, the transmit switch is turned on.

4. The filter circuit according to claim 1 , further comprising:
a termination resistor; and
a termination switch connected between the node and the termination resistor.

5. The filter circuit according to claim 4 ,
wherein when none of the first band and the second band is used for communication, the receive switch and the transmit switch are turned off, and the termination switch is turned on.

6. The filter circuit according to claim 1 , wherein
the first receive band of the first band and the second transmit band of the second band partially overlap and are different,
a part of the first receive band of the first band does not overlap with the second transmit band of the second band and/or a part of the second transmit band of the second band does not overlap with the first receive band of the first band.

7. The filter circuit according to claim 1 , wherein
at least one of the first band and the second band is of an FDD system.

8. The filter circuit according to claim 1 , further comprising:
a controller configured to:
change the passband of the variable filter to the first receive band of the first band, turn on the receive switch, and turn off the transmit switch when the reception signal in the first receive band is received; and
change the passband of the variable filter to the second transmit band of the second band, turn off the receive switch, and turn on the transmit switch when the transmission signal in the second transmit band is transmitted.

9. A front end circuit comprising:
a first filter circuit and a second filter circuit that are the filter circuits according to claim 1 of which the common terminals are connected to an antenna terminal.

10. The front end circuit according to claim 9 , further comprising:
a first switch connected between the antenna terminal and the common terminal of the first filter circuit; and
a second switch connected between the antenna terminal and the common terminal of the second filter circuit.

11. The front end circuit according to claim 10 , wherein
the first receive band of the first filter circuit and the second transmit band of the second filter circuit are included in a same E-UTRA operating band, and
when transmission and reception of the same E-UTRA operating band are performed, the first switch, the second switch, the receive switch of the first filter circuit, and the transmit switch of the second filter circuit are turned on, and the transmit switch of the first filter circuit and the receive switch of the second filter circuit are turned off.

12. A module comprising:
a substrate; and
the variable filter, the receive switch, and the transmit switch of the filter circuit according to claim 1 mounted on the substrate.

13. The filter circuit according to claim 1 , wherein the variable filter includes:
an acoustic wave resonator; and
an adjustment circuit that is connected in parallel and/or series to the acoustic wave resonator and configured to change an impedance thereof.

14. A filter circuit, comprising:
a variable filter that is connected between a common terminal and a node and configured to change of a passband thereof;
a receive switch connected between a receive terminal, from which a reception signal in a first receive band of a first band is output, and the node, said first band being corresponding to an E-UTRA operating band and including a first transmit band and said first receive band, a reception signal in the first receive band being output from the receive terminal; and
a transmit switch connected between a transmit terminal, to which a transmission signal in a second transmit band of a second band is input, and the node, said second band being corresponding to an E-UTRA operating band that is different from the first band and including said second transmit band and a second receive band,
wherein a difference between a high-frequency end of the first receive band and a high-frequency end of the second transmit band is smaller than a difference between the high-frequency end of the first receive band and a high-frequency end of the first transmit band and a difference between a high-frequency end of the second receive band and the high-frequency end of the second transmit band,
wherein a difference between a low-frequency end of the first receive band and a low-frequency end of the second transmit band is smaller than a difference between the low-frequency end of the first receive band and a low-frequency end of the first transmit band and a difference between a low-frequency end of the second receive band and the low-frequency end of the second transmit band,
wherein the variable filter includes:
an acoustic wave resonator;
a first capacitor connected in parallel to the acoustic wave resonator between a first node and a second node;
a pathway that is connected in se

Assignees

• Taiyo Yuden Kk

Inventors

• Saji Tetsuo

Classifications

• H03H2210/025

  Capacitor · CPC title

• H03H9/542

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

• H04L5/001

  the frequencies being arranged in component carriers · CPC title

• H03H9/6403

  Programmable filters · CPC title

• H03H2210/012

  Centre frequency; Cut-off frequency · CPC title