Surface acoustic wave device

• US 20010028286A1
• Filed: 03/05/2001
• Published: 10/11/2001
• Est. Priority Date: 03/10/2000
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Takamine, Yuichi
• Granted Patent: US 6,606,016 B2
• Time in Patent Office: Days
• US Class Current: 333/193
• CPC Class Codes: H03H 2250/00 Indexing scheme relating to dual- or multi-band filters
• CPC Class Codes: H03H 9/0028 using surface acoustic wave devices
• CPC Class Codes: H03H 9/6423 Means for obtaining a particular transfer characteristic
• CPC Class Codes: H03H 9/6436 having one acoustic track only
• CPC Class Codes: H03H 9/6473 the electrodes being electrically interconnected
• CPC Class Codes: H03H 9/6476 the tracks being electrically parallel

Abstract

A surface acoustic wave device includes a first surface acoustic wave filter connected between an input terminal and an output terminal, a second surface acoustic wave filter having a different center frequency from that of the first surface acoustic wave filter, and which is connected between the input terminal and the output terminal and in parallel with the first surface acoustic wave filter, and at least one one-port surface acoustic wave resonator connected in series with the first or second surface acoustic wave filter, on at least one side between the input terminal and at least one of the first and second surface acoustic wave filters, or between the output terminal and at least one of the first and second surface acoustic wave filters. The anti-resonance frequency of the one one-port surface acoustic wave resonator is positioned on the side of higher frequencies than those of the pass band of the surface acoustic wave filter disposed on the side where the one-port surface acoustic wave resonator is connected in series.

Claims

1. A surface acoustic wave device comprising:

a first surface acoustic wave filter connected between an input terminal and an output terminal;

a second surface acoustic wave filter having a different center frequency than that of said first surface acoustic wave filter, and which is connected between said input terminal and said output terminal and in parallel with said first surface acoustic wave filter; and

at least one one-port surface acoustic wave resonator connected in series with the first surface acoustic wave filter or the second surface acoustic wave filter, on at least one side between said input terminal and at least one of said first and second surface acoustic wave filters, or between said output terminal and at least one of said first and second surface acoustic wave filters;

wherein

the anti-resonance frequency of said one one-port surface acoustic wave resonator is positioned on the side of higher frequencies than those of the pass band of the surface acoustic wave filter disposed on the side where said one-port surface acoustic wave resonator is connected in series.

2. A surface acoustic wave device as claimed in

claim 1

, wherein the center frequency of the second surface acoustic wave filter is higher than that of the first surface acoustic wave filter.

3. A surface acoustic wave device as claimed in

claim 2

, wherein a first one-port surface acoustic wave resonator is connected in series between the second surface acoustic wave filter and the input terminal, and a second one-port surface acoustic wave resonator is connected in series between the second surface acoustic wave filter and the output terminal.

4. A surface acoustic wave device as claimed in

claim 1

, wherein a plurality of said one-port surface acoustic wave resonators are connected in a multi-stage series connection.

5. A surface acoustic wave device as claimed in

claim 1

, wherein at least two of said one-port surface acoustic wave resonators are connected in series, on at least one side between said first or second surface acoustic wave filter and the input terminal, or between said first or second surface acoustic wave filter and the output terminal.

6. A surface acoustic wave device as claimed in

claim 5

, wherein said plurality of one-port surface acoustic wave resonators which are connected in series with each other, differ in the frequency determined by the pitch of the interdigital transducers thereof, from each other.

7. A surface acoustic wave device as claimed in

claim 1

, wherein in at least one one-port surface acoustic wave resonator of said one-port surface acoustic wave resonators, the interdigital transducers are weighted.

8. A surface acoustic wave device as claimed in

claim 1

, wherein each of said first and second surface acoustic wave filters is a longitudinally-coupled surface acoustic wave filter having three IDTs disposed along the surface wave propagation direction.

9. A surface acoustic wave device as claimed in

claim 8

, wherein in said first and second longitudinally-coupled surface acoustic wave filters each having three IDTs, the first and second longitudinally-coupled surface acoustic wave filters are connected in parallel with each other so that the IDTs on both sides in the surface wave propagation direction, of said first and second longitudinally-coupled surface acoustic wave filters share the input terminal therebetween, and so that the center IDTs of said first and second longitudinally-coupled surface acoustic wave filters share the output terminal therebetween.

10. A surface acoustic wave device as claimed in

claim 1

, further comprising an inductance element additionally connected in parallel with each of said input and output terminals.

11. A surface acoustic wave device as claimed in

claim 10

, wherein the inductance value of the inductance element additionally connected in parallel with said input terminal differs from the inductance value of the inductance element additionally connected in parallel with said output terminal.

12. A surface acoustic wave device as claimed in

claim 1

, wherein the electrode film thickness of said first surface acoustic wave filter differs from that of said second surface acoustic wave filter.

13. A surface acoustic wave device as claimed in

claim 1

, wherein said first surface acoustic wave filter and said second surface acoustic wave filter are connected in parallel with each other on a piezoelectric substrate.

14. A surface acoustic wave device as claimed in

claim 1

, wherein at least one of said input terminal and said output terminal are balanced-signal terminals.

15. A communication device comprising:

a surface acoustic wave device as claimed in

claim 1

, defining a band-pass filter; and

a mounting substrate mounting the surface acoustic wave device.