FILTER DEVICE

• US 20150137909A1
• Filed: 01/27/2015
• Published: 05/21/2015
• Est. Priority Date: 08/30/2012
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: OKUDA, Tetsuro, KAWASAKI, Koichiro
• Granted Patent: US 9,356,576 B2
• Time in Patent Office: Days
• US Class Current: 333/133
• CPC Class Codes: H03H 7/01 Frequency selective two-port networks
• CPC Class Codes: H03H 7/46 Networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source for use in multiplex transmission systems H04J1/00
• CPC Class Codes: H03H 9/0009 using surface acoustic wave devices
• CPC Class Codes: H03H 9/0057 the balanced terminals being on the same side of the tracks
• CPC Class Codes: H03H 9/0571 including bulk acoustic wave [BAW] devices
• CPC Class Codes: H03H 9/0576 including surface acoustic wave [SAW] devices
• CPC Class Codes: H03H 9/46 Filters multiple-port electromechanical filters H03H9/70
• CPC Class Codes: H03H 9/6483 Ladder SAW filters
• CPC Class Codes: H03H 9/706 Duplexers
• CPC Class Codes: H03H 9/725 Duplexers

Abstract

A filter device includes a first signal terminal, a second signal terminal, a filter unit, a first inductor and a second inductor. The filter unit is connected between the first signal terminal and the second signal terminal. The first inductor is connected between a connection point between the filter unit and the first signal terminal, and a ground potential. The second inductor is connected between the filter unit and the second signal terminal. The second inductor is electromagnetically coupled with the first inductor.

Claims

1. (canceled)

2. A filter device comprising:

a first signal terminal;

a second signal terminal;

a filter unit connected between the first signal terminal and the second signal terminal;

a first inductor connected between a connection point between the filter unit and the first signal terminal, and a ground potential; and

a second inductor connected between the filter unit and the second signal terminal and electromagnetically coupled with the first inductor.

3. The filter device according to claim 2, further comprising:

a substrate;

an inductor chip defining the first inductor and mounted on the substrate; and

a wiring line that is provided inside the substrate and defines the second inductor.

4. The filter device according to claim 3, wherein the inductor chip and the wiring line face each other in a thickness direction of the substrate.

5. The filter device according to claim 4, wherein the inductor chip and the wiring line face each other without there being any electrodes therebetween.

6. The filter device according to claim 2, further comprising:

a third signal terminal; and

one other filter unit connected between a connection point between the first signal terminal and the filter unit, and the third signal terminal;

wherein

the other filter unit and the filter unit have different pass bands; and

the first and second inductors are configured such that a signal that has a phase and amplitude that weaken a signal located in a passband of the other filter unit that passes through the filter unit flows from one of the first and second signal terminals to the other of the first and second signal terminals by passing through the first and second inductors, which are electromagnetically coupled with each other, and not passing through the filter unit.

7. The filter device according to claim 6, wherein the first and second inductors are configured such that a signal that has a phase that is opposite to that of a signal of at least a portion of a frequency band of the signals located in the passband of the other filter unit that passes through the filter unit flows from one of the first and second signal terminals to the other of the first and second signal terminals by passing through the first and second inductors, which are electromagnetically coupled with each other and not passing through the filter unit.

8. The filter device according to claim 7, wherein the first and second inductors are configured such that the signal of at least a portion of the frequency band of the signals located in the passband of the other filter unit that passes through the filter unit and the signal that flows from one of the first and second signal terminals to the other of the first and second signal terminals by passing through the first and second inductors, which are electromagnetically coupled with each other, and not passing through the filter unit have phases opposite to each other and the same amplitude.

9. The filter device according to claim 2, wherein the filter unit is an unbalanced filter unit that outputs an unbalanced signal.

10. The filter device according to claim 2, wherein

the first signal terminal is an antenna signal terminal that is connected to an antenna;

the second signal terminal is a transmission signal terminal that is connected to a transmission circuit; and

the filter unit is a ladder-type elastic wave filter circuit that includes a series arm resonator and a parallel arm resonator.

11. The filter device according to claim 6, wherein the third signal terminal is a reception signal terminal that is connected to a reception circuit;

and

the other filter unit is a longitudinally coupled resonator type elastic wave filter circuit.

12. The filter device according to claim 6, wherein the other filter unit is one of a balanced filter unit and an unbalanced filter unit.

13. The filter device according to claim 6, wherein the filter unit is a transmission filter unit and the other filter unit is a reception filter unit.

14. The filter device according to claim 2, wherein the first and second inductors are inductors configured to adjust impedance and to define a sub-route to increase attenuation in a reception frequency band in the filter unit.

15. The filter device according to claim 14, wherein the sub-route is provided between the first signal terminal and the second terminal and passes through the first and second inductors, which are electromagnetically coupled with each other, but does not pass through the filter unit.

16. The filter device according to claim 2, wherein the second inductor is defined by a wiring line in a substrate.

17. The filter device according to claim 2, wherein the filter unit is the only filter unit in the filter device.

18. The filter device according to claim 2, wherein the second inductor is connected to one of a reception filter unit and a filter unit configured to receive a global positioning system signal.