Surface acoustic wave device

• US 4,748,364 A
• Filed: 03/20/1987
• Issued: 05/31/1988
• Est. Priority Date: 10/15/1984
• Status: Expired due to Fees

• Current Assignee: Clarion Co., Ltd. (Faurecia SA)
• Original Assignee: Clarion Co., Ltd. (Faurecia SA)
• Inventors: Mitsutsuka, Syuichi
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US07/028,284
• Time in Patent Office: 438 Days
• Field of Search: 310/313 R, 310/313 A, 310/313 B, 310/313 C, 310/313 D, 333/193-196, 333/150-155
• US Class Current: 310/313.00D
• CPC Class Codes: H03H 2240/00 Indexing scheme relating to filter banks
• CPC Class Codes: H03H 9/02629 of the edges
• CPC Class Codes: H03H 9/14547 Fan shaped; Tilted; Shifted; Slanted; Tapered; Arched; Stepped finger transducers
• CPC Class Codes: H03H 9/14558 Slanted, tapered or fan shaped transducers H03H9/14561, H03H9/14564 take precedence
• CPC Class Codes: H03H 9/14564 Shifted fingers transducers
• CPC Class Codes: H03H 9/14567 Stepped-fan shaped transducers
• CPC Class Codes: H03H 9/14594 Plan-rotated or plan-tilted transducers
• CPC Class Codes: H03H 9/423 with adjustable delay time
• CPC Class Codes: H03H 9/6403 Programmable filters
• CPC Class Codes: H03H 9/72 Networks using surface acoustic waves

Abstract

A surface acoustic wave device includes a semiconductor substrate, a piezoelectric film disposed on the semiconductor substrate, at least one pair of comb-shaped electrodes constituting an input transducer and an output transducer, a plurality of surface acoustic wave filters having different bands which include a plurality of metal electrodes, so disposed that each of them is located between the input and output comb-shaped electrodes of each of the surface, acoustic wave filters, a bias voltage applying arrangement for applying bias voltages to each of the metal electrodes; and a bias voltage regulating arrangement for regulating the bias voltages.

Claims

1. A surface acoustic wave device comprising:

a semiconductor substrate;

A piezoelectric film provided on said semiconductor substrate;

an input transducer and an output transducer provided at spaced locations on said piezoelectric film, wherein a surface acoustic wave travelling through said piezoelectric film from said input transducer to said output transducer has respective portions which travel along respective paths of travel;

a plurality of elongate metal electrodes provided on said piezoelectric film between said input transducer and said output transducer, each said metal electrode being positioned along a respective said surface acoustic wave path of travel so as to extend parallel to a direction in which surface acoustic waves travel along the path;

bias voltage applying means for applying to each of said metal electrodes a respective bias voltage; and

bias voltage regulating means for independently regulating said bias voltages so as to control the respective propagation losses of surface acoustic waves traveling past each said metal electrode along a respective said path of travel.

2. A surface acoustic wave device according to claim 1, wherein said input transducer includes at least one pair of comb-shaped input electrodes, and wherein said output transducer includes a plurality of pairs of comb-shaped output electrodes which are disposed so that each corresponds to a respective one of said metal electrodes and receives surface acoustic waves propagating along a respective one of said paths of travel.

3. A surface acoustic wave device according to claim 1, wherein said input transducer and said output transducer each include a single pair of comb-shaped electrodes having a plurality of fingers, said comb-shaped electrodes of said output transducer being formed so that the spacing between the fingers varies discontinuously in a direction approximately perpendicular to said paths of travel of surface acoustic waves.

4. A surface acoustic wave device according to claim 1, wherein said input transducer and said output transducer each include a single pair of comb-shaped electrodes having a plurality of fingers, said comb-shaped electrodes of said output transducer being so formed that the spacing between the fingers varies continuously in a direction approximately perpendicular to said paths of travel of surface acoustic waves.

5. A surface acoustic wave device according to claim 1, wherein said input transducer includes a plurality of pairs of comb-shaped input electrodes which have identical input characteristics and which are disposed so that each corresponds to a respective one of said metal electrodes and produces surface acoustic waves which travel along a respective one of said paths of travel.

6. A surface acoustic wave device according to claim 1, wherein said input transducer includes a plurality of pairs of comb-shaped input electrodes which have different input characteristics and which are disposed so that each corresponds to a respective one of said metal electrodes and produces surface acoustic waves which travel along a respective one of said paths of travel, each said pair of said comb-shaped input electrodes being provided with an input signal through a respective matching circuit.

7. A surface acoustic wave device according to claim 1, wherein said input transducer includes at least one pair of comb-shaped input electrodes, wherein said output transducer includes a plurality of pairs of comb-shaped output electrodes which are disposed so that each corresponds to a respective one of said metal electrodes and is responsive to surface acoustic waves which travel along a respective one of said paths of travel, and wherein said paths of travel of surface acoustic waves between said input electrode and said output electrodes are different from each other.

8. A surface acoustic wave device according to claim 1, wherein said input transducer includes at least one pair of comb-shaped input electrodes and said output transducer includes at least one pair of comb-shaped output electrodes, said comb-shaped output electrodes being positioned so that the distance between each said pair of input electrodes and a corresponding said pair of output electrodes varies in a direction perpendicular to said paths of travel of surface acoustic waves.

9. A surface acoustic wave device according to claim 1, including an insulating film provided between said semiconductor substrate and said piezoelectric film.

10. A surface acoustic wave device according to claim 1, wherein said semiconductor substrate has first and second surfaces provided on opposite sides thereof, said piezoelectric film being provided on said first surface of said semiconductor substrate, and wherein said bias voltage applying means includes an earth electrode provided on said second surface of said semiconductor substrate, said bias voltage applying means applying each said bias voltage between said earth electrode and a respective one of said metal electrodes.