SPLIT SURFACE WAVE ACOUSTIC DELAY LINE

• US 3,568,102 A
• Filed: 07/06/1967
• Issued: 03/02/1971
• Est. Priority Date: 07/06/1967
• Status: Expired due to Term

• Current Assignee: Tseng Chin Chong
• Original Assignee: Tseng Chin Chong
• Inventors: TSENG CHIN CHONG
• Application Number:
  US04/651,530
• Time in Patent Office: 1,335 Days
• US Class Current: 333/153
• CPC Class Codes: H03H 9/42 using surface acoustic waves devices for manipulating acoustic surface waves in general G10K11/36

Abstract

An acoustic delay line having an input and a plurality of output transducers is provided which includes at least one reflective grating, a plurality of adjacent spaced conductive strips, coupled to the surface of a piezoelectric layer for splitting an acoustic surface wave traveling across the surface of the piezoelectric layer into two components, one of which continues to travel in the original direction and the other of which travels skew to that direction. Each of the original and reflected portions are detected by the output transducers. Significantly, the reflective grating affords the basis for multiple output delay lines of various apparent applications, of structural simplicity and of minimal interference between input and output transducers.

Claims

1. An acoustic surface wave device comprising in combination:

A layer of piezoelectric material having a smooth surface input acoustic surface wave transducer means coupled to said surface of said layer for converting electrical signals supplied thereto into an acoustic surface wave which travels along the surface of said layer in at least one predetermined first path of travel;

a reflective grating comprising a plurality of spaced strips of metallic material coupled to said surface of said layer and positioned across and skew to said first path of travel for reflecting a portion of said acoustic surface wave along a second path on said surface skew to said first path and permitting the passage of the remaining portion of said acoustic surface wave substantially in said first path of travel along said surface; and

output acoustic surface wave transducer means spaced from said input transducer means coupled to said surface of said layer in said second path of travel for producing an electrical output signal in response to passage of said reflected portion of said acoustic surface wave.

2. The invention as defined in claim 1 further comprising a final output transducer means coupled to said surface of said layer at a predetermined position in said first path on the side of said reflective grating opposite said input transducer for producing an electrical output signal in response to the passage of said remaining portion of said acoustic surface wave.

3. The invention as defined in claim 1 wherein said plurality of strips in said reflective grating are spaced apart a predetermined distance and parallel and aligned skew to said first path.

4. The invention as defined in claim 3 wherein each of said transducer means and said output transducer means further comprise a plurality of adjacent spaced parallel conductive strips and means to connect adjacent strips to opposite polarity terminals.

5. The invention as defined in claim 4 wherein said strips comprising said transducer means contain elongated front and back edges and one of said edges of at least one of said strips is spaced from a corresponding one of said edges of an adjacent strip by a distance of lambda /2 where lambda v/f and f is a predetermined input signal frequency and v is the acoustic velocity in said layer.

6. The invention as defined in claim 3 wherein said conductive strips comprising said reflective grating and said first path defines a predetermined angle, Theta , and wherein each one of said adjacent spaced parallel strips comprising said reflective grating possess elongated front and back edges and wherein at least one of the said edges of one of said strips is spaced from a corresponding edge of an adjacent strip by a distance, d, which is substantially equal to n lambda /2 sin Theta , where n is an integer, and lambda is the acoustic wavelength in said layer of a predetermined frequency, f.

7. The invention as defined in claim 6 wherein each of said edges and corresponding edges comprises a front edge.

8. The invention as defined in claim 3 wherein said conductive strips comprising each reflective grating and said first path defines a predetermined angle, Theta , wherein adjacent strips in each reflective grating are spaced by a distance, s, and have a width, t, and s+t is substantially equal to n lambda /2 sin Theta , where n is an integer and lambda is the acoustic wavelength in said layer of a predetermined frequency, f.

9. In combination:

A layer of piezoelectric material having a smooth surface;

transducer means coupled to said surface for converting electrical signals supplied thereto into an acoustic surface wave which travels along the surface of said layer in at least one predetermined first path;

a plurality of reflective gratings of metAllic material coupled to said surface and spaced from one another in said first path along the surface of said layer;

each of said reflective gratings responsive to an incident acoustic surface wave for reflecting a portion thereof in a path along said surface skew to said first path and permitting passage of the remaining portion thereof in said first path of travel;

a plurality of output transducers corresponding to the plurality of reflective gratings and spaced along said surface;

each one of said output transducers being coupled to the surface of said layer confronting a corresponding one of said plurality of reflective gratings and located substantially in said path of travel of said reflected portion of said acoustic surface wave reflected from said corresponding reflective grating and responsive to the incidence of an acoustic surface wave for producing an electrical output signal.

10. The invention as defined in claim 9 further comprising an additional output transducer coupled to said layer and located in said path of travel of said acoustic surface wave and beyond the last one of said plurality of reflective gratings for producing an electrical output signal in response to the incidence of an acoustic surface wave.

11. The invention as defined in claim 10 wherein each of said plurality of said reflective gratings comprise a plurality of adjacent spaced parallel conductive strips coupled to said surface and skew to said first path of travel of said acoustic surface wave.

12. The invention as defined in claim 11 wherein each of said input and output transducers comprise a plurality of interdigitated thin conductive strips.

13. The invention as defined in claim 11 wherein said conductive strips comprising each said reflective grating and said first path define a predetermined angle, Theta , and wherein each one of said adjacent spaced parallel strips comprising each said reflective grating possess elongated front and back edges, and wherein at least one of the said edges of one of said strips is spaced from a corresponding edge of an adjacent strip by a distance, d, which is substantially equal to n lambda /2 sin Theta , where n is an integer, and lambda is the acoustic wavelength in said layer of a predetermined frequency, f.

14. The invention as defined in claim 13 wherein each of said edges and corresponding edges comprises a front edge.

15. The invention as defined in claim 11 wherein said conductive strips comprising each reflective grating and said first path define a predetermined angle, Theta , and wherein adjacent strips in each reflective grating are spaced by a distance, s, and have a width, t, and s+t is substantially equal to n lambda /2 sin Theta , where n is an integer and is the acoustic wavelength in said layer of a predetermined frequency, f.

16. The invention as defined in claim 15 wherein said strips comprising said transducer means contain elongated front and back edges and one of said edges of at least one of said strips is spaced from a corresponding one of said edges of an adjacent strip by a distance of lambda /2, where lambda v/f and f is a predetermined input signal frequency and v is the acoustic velocity in said layer.

17. An acoustic surface wave device comprising in combination:

A piezoelectric layer having a flat surface capable of sustaining the propagation of an acoustic surface wave at a predetermined first velocity;

first acoustic surface wave transducer means coupled to said surface of said piezoelectric layer and responsive to an electrical input signal for producing a corresponding acoustic surface wave for travel in a first direction;

a thin metallic coating having a major axis inclined at an angle to said first direction of travel located on a portion of said surface of said piezoelectric layer at a predetermined position spaced from said input transducer and from any edges of said piezoelectric layer for lowering the Acoustic velocity with which an acoustic surface wave travels thereby to create a difference in the acoustic propagation velocity between the coated and uncoated portions of said layer whereby a portion of any acoustic surface wave is reflected along said surface in a second direction skew to its original direction of propagation; and

second acoustic surface wave transducer means coupled to said surface responsive to a reflected acoustic surface wave traveling in said second direction for providing an electrical output signal corresponding thereto.