SURFACE ACOUSTIC WAVE PHASE CONTROL DEVICE

• US 3,845,420 A
• Filed: 03/02/1973
• Issued: 10/29/1974
• Est. Priority Date: 03/02/1973
• Status: Expired due to Term

• Current Assignee: Harrison H. Barrett, Manfred B. Schulz, Melvin G. Holland
• Original Assignee: Harrison H. Barrett, Manfred B. Schulz, Melvin G. Holland
• Inventors: Holland, Melvin G., Schulz, Manfred B., Barrett, Harrison H.
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Nussbaum, Marvin
• Application Number:
  US05/337,346
• Time in Patent Office: 606 Days
• Field of Search: 333/3R,72 310/9.7,9.8
• US Class Current: 333/153
• CPC Class Codes: H03H 9/423 with adjustable delay time

Abstract

A surface acoustic wave device in which a phase or velocity shifting electrically conductive layer is located between the receiving and transmitting transducers. In one embodiment as a filter, the phase shift may be varied as a function of frequency over a broad range of frequencies by varying the shape of the conductive layer thereby permitting a desired phase response to be achieved.

Claims

1. In combination:

means for propagating a surface wave in a piezoelectric material; and

means for varying the velocity of said surface wave over at least a portion of said piezoelectric material, the velocity of said surface wave over said portion of said piezoelectric material being substantially independent of the mass of said velocity varying means and said velocity varying means operating independently of mechanical properties of said piezoelectric material said velocity varying means having a thickness in the range of 100 A to 300 A.

2. The combination according to claim 1 wherein said propagating means comprises:

a slice of piezoelectric material; and

means for inducing said surface wave in said slice of piezoelectric material.

3. The combination according to claim 2 wherein said inducing means comprises a transducer for converting an electrical signal into a mechanical signal in said piezoelectric material.

4. The combination according to claim 2 wherein said piezoelectric material is lithium niobate.

5. The combination according to claim 1 wherein said velocity varying means comprises gold.

6. The combination according to claim 1 wherein said velocity varying means comprises aluminum.

7. The combination according to claim 1 wherein said velocity varying means comprises a photoconductive material.

8. The combination according to claim 1 further comprising transducer means for converting said surface wave to an electrical signal.

9. The combination according to claim 8 further comprising utilization means for varying the phase of signals in a radar system.

10. The combination according to claim 8 further comprising utilization means in a receiver circuit.

11. In combination:

a slice of piezoelectric material having at least one substantially smooth surface;

first transducer means for converting an electrical signal into a surface wave on said substantially smooth surface of said slice of piezoelectric material, said first transducer means being adjacent to said substantially smooth surface;

second transducer means for producing an electrical signal in response to said surface wave; and

means for varying the velocity of said surface wave comprising a sheet of conductive material adjacent to said substantially smooth surface located between said first and second transducer means, the velocity of said surface wave on said substantially smooth surface being substantially independent of the mass of said sheet and said velocity varying means operating independently of mechanical properties of said piezoelectric material, said velocity varying means having a thickness in the range of 100 A to 300 A.

12. The combination according to claim 11 wherein said first and second transducer means each comprise interleaved pairs of conductive strips.

13. The combination according to claim 11 wherein said sheet of conductive material comprises a layer of aluminum.

14. The combination according to claim 11 wherein said sheet of conductive material comprises a layer of gold.

15. A surface wave device having input and output terminals comprising in combination:

a slice of piezoelectric material;

means for inducing surface waves in said piezoelectric material, surface waves of different frequencies propagating over different portions of said slice of piezoelectric material;

means for varying the velocity of said surface waves over at least a portion of said slice of piezoelectric material, the proportion by which said velocity is varied being dependent upon said frequencies.

16. The combination of claim 15 wherein said velocity varying means comprises a sheet of conductive material.

17. The combination of claim 16 wherein surface dimensions of said sheet of conductive material are preselected in accordance with preferred frequency characteristics of said device.

18. The combination of claim 17 wherein said sheet of conductive material is aluminum, said sheet of conductive material having a thickness between 100 A and 300 A.