Saw filter with an attenuation pole including a band-pass ladder type of saw filter having a saw resonator

• US 20020089396A1
• Filed: 11/16/2001
• Published: 07/11/2002
• Est. Priority Date: 01/11/2001
• Status: Active Grant

• Current Assignee: Mind Fusion, LLC (Ascend Innovation Management, LLC)
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Komazaki, Tomokazu, Fujita, Yoshiaki, Terada, Satoshi, Noguchi, Kazushige, Kihara, Yoshikazu
• Granted Patent: US 6,677,835 B2
• Time in Patent Office: Days
• US Class Current: 333/193
• CPC Class Codes: H03H 9/6483 Ladder SAW filters

Abstract

A polar SAW (Surface Acoustic Wave) filter includes a band-pass ladder type SAW filter having a SAW resonator. A two-terminal pair circuit is serially connected to the band-pass ladder type SAW filter and includes a plurality of inductors. The polar SAW filter has attenuation poles in each of the higher-frequency and lower-frequency attenuation ranges of a pass band.

Claims

1. A polar SAW (Surface Acoustic Wave) filter comprising:

a band-pass ladder type of SAW filter having an input port and an output port, and comprising a first SAW resonator interconnected between the input and output ports; and

a two-terminal pair circuit serially connected to said SAW filter and comprising a plurality of inductors.

2. The polar SAW filter in accordance with claim 1, wherein said band-pass ladder type of SAW filter comprises a second SAW resonator connected to the input port and a third SAW resonator connected to the output port to form parallel arm resonators,

said plurality of inductors being three inductors interconnected in a π

configuration.

3. The polar SAW filter in accordance with claim 2, wherein one of said three inductors has one end interconnected to said second SAW resonator and another end interconnected to said third SAW resonator.

4. The polar SAW filter in accordance with claim 1, wherein said band-pass ladder type of SAW filter comprises a second SAW resonator connected to the input port and a third SAW resonator connected to the output port to form parallel arm resonators,

said plurality of inductors being three inductors being interconnected in a T configuration.

5. The polar SAW filter in accordance with claim 2, further comprising a package or chip on which said polar SAW filter is fabricated,

at least one of said plurality of inductors being in a form of either of an electrode pattern and a bonding wire connected to any of said second and third SAW resonators.

6. A polar SAW filter comprising:

a first serial arm SAW resonator having a first and a second electrode connected to an input port and an output port, respectively;

a first parallel arm SAW resonator having a first electrode connected to the input port;

a second parallel arm SAW resonator having a first electrode connected to the output port;

a first inductor having a first terminal connected to a second electrode of said first parallel arm SAW resonator and a second terminal connected to a ground terminal;

a second inductor having a first terminal connected to a second electrode of said second parallel arm SAW resonator and a second terminal connected to the ground terminal; and

a third inductor having a first terminal connected to the second electrode of said first parallel arm SAW resonator and a second terminal connected to the second electrode of said second parallel arm SAW resonator.

7. The polar SAW filter in accordance with claim 6, further comprising:

a second serial arm SAW resonator having a first and a second electrode connected to the input port and the first electrode of said first serial arm SAW resonator, respectively;

a third parallel arm SAW resonator having a first electrode connected to the input port; and

a fourth inductor having a first terminal connected to a second electrode of said third parallel arm SAW resonator and a second terminal connected to the ground terminal.

8. The polar SAW filter in accordance with claim 6, further comprising a supporting member in a form of package or chip on which said polar SAW filter is fabricated, said first, second and third inductors being in a form of electrical connection formed on said supporting member.

9. The polar SAW filter in accordance with claim 8, wherein said first and second inductors are in a form of bonding wire formed on said supporting member and connecting the second electrodes of said first and second parallel SAW resonators to the ground terminal.

10. The polar SAW filter in accordance with claim 8, wherein said third inductor is in a form of electrode pattern formed on said supporting member and connecting the second electrodes of said first and second parallel SAW resonators to each other.

11. The polar SAW filter in accordance with claim 8, wherein said first, second and third inductors are in a form of bonding wire formed on said supporting member and connecting the second electrodes of said first and second parallel SAW resonators to the ground terminal, and to each other, respectively.

12. The polar SAW filter in accordance with claim 7, further comprising a supporting member in a form of package or chip on which said polar SAW filter is fabricated, said first, second, third and fourth inductors being in a form of electrical connection formed on said supporting member.

13. The polar SAW filter in accordance with claim 12, wherein said first, second and third inductors are in a form of bonding wire formed on said supporting member and connecting the second electrodes of said first, second and third parallel SAW resonators to the ground terminal.

14. The polar SAW filter in accordance with claim 12, wherein said third inductor is in a form of electrode pattern formed on said supporting member and connecting the second electrodes of said first and second parallel SAW resonators to each other.

15. The polar SAW filter in accordance with claim 12, wherein said first, second, third and fourth inductors are in a form of bonding wire formed on said supporting member and connecting the second electrodes of said first, second and third parallel SAW resonators to the ground terminal, and the second electrodes of said first and second parallel SAW resonators to each other, respectively.