Apparatus and method for phase-encoded surface wave devices

• US 3,931,597 A
• Filed: 02/04/1974
• Issued: 01/06/1976
• Est. Priority Date: 02/04/1974
• Status: Expired due to Term

• Current Assignee: Magnavox (Koninklijke Philips N.V.)
• Original Assignee: Magnavox (Koninklijke Philips N.V.)
• Inventors: Hunsinger, Bill J., Cho, Frederick Y.
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Nussbaum, Marvin
• Application Number:
  US05/439,482
• Time in Patent Office: 701 Days
• Field of Search: 333/30 R, 333/72, 310/9.8
• US Class Current: 333/154
• CPC Class Codes: G06K 19/0675 the resonating marks being of the surface acoustic wave [SAW] kind SAW devices per se H03H9/64
• CPC Class Codes: H03C 3/42 by means of electromechanical devices H03C3/28 takes precedence
• CPC Class Codes: H03H 9/1452 by finger overlap length, apodisation
• CPC Class Codes: H03H 9/14535 Position weighting
• CPC Class Codes: H03H 9/14547 Fan shaped; Tilted; Shifted; Slanted; Tapered; Arched; Stepped finger transducers
• CPC Class Codes: H03H 9/14564 Shifted fingers transducers
• CPC Class Codes: H03H 9/6406 Filters characterised by a particular frequency characteristic

Abstract

Apparatus and method for phase-encoding electro-acoustic electro-acoustic elements, elements of an acoustic surface wave device to provide preselected transducer characteristics. By altering the position of a transducer element or portions of a transducer element, the phase of the acoustic wave propagated from, or the phase of the electrical signal received by the transducer element can be varied by an amount determined by the velocity of propagation of the acoustic wave.

By altering the location of the electro-elements, or portions thereof, from a position determined for example by amplitude-encoding techniques, a resultant signal produced by a plurality of electro-acoustic elements, element portions, or combination of elements and element portions can provide the preselected transducer characteristics. In addition, the elements or element portions can be located such that the overlap amplitude between adjacent electro-acoustic elements is substantially a constant, providing increased directionality for acoustic waves orignating at the transducer.

According to one embodiment, each electro-acoustic transducer can be phase-encoded permitting both an input and an output transducer to be phase-encoded with preselected characteristics.

According to a second embodiment, the elements or portions thereof of a first transducer are displaced relative to elements or portions thereof of a second transducer to provide appropriate device phase-encoding.

Claims

1. An electro-acoustic transducer for providing predetermined frequency characteristics, comprising:

an acoustic-wave propagating medium;

a first group of electrically-coupled conducting elements being substantially perpendicular to a first bus bar region connecting all the conducting elements of the first group, said first element group mechanically coupled to said medium;

a second group of electrically-coupled conducting elements being substantially perpendicular to a second bus bar region connecting all the conducting elements of the second group, said second element group mechanically coupled to said medium, wherein said first group of elements and said second group of elements are interleaved, a plurality of elements of said first and said second group of elements including electrically-coupled element sections, wherein at least one of said coupled sections of the plurality of elements is displaced from a predetermined position so as to be in a plane parallel to the element section to which it is electrically-coupled; and

said predetermined position corresponds to a local maxima of a time domain diagram for each of said elements of said first group and wherein said predetermined position is related to local minima for each of said elements of said second group.

2. An electro-acoustic transducer for providing predetermined frequency characteristics, comprising:

an acoustic-wave propagating medium;

a first group of electrically-coupled conducting elements being substantially perpendicular to a first bus bar region connecting all the conducting elements of the first group, said first element group mechanically coupled to said medium;

a second group of electrically-coupled conducting elements being substantially perpendicular to a second bus bar region connecting all the conducting elements of the second group, said second element group mechanically coupled to said medium, wherein said first group of elements and said second group of elements are interleaved, a plurality of elements of said first and said second group of elements including electrically-coupled element sections, wherein at least one of said coupled sections of the plurality of elements is displaced so as to be in a plane parallel to the element section to which it is electrically-coupled; and

wherein displacement of said at least one coupled section results in a signal of preestablished amplitude for one of said plurality of elements including said at least one coupled section, and wherein said preestablished amplitude corresponds to a local maxima of a time domain representation for an element of said first group.

3. An electro-acoustic device for providing predetermined frequency characteristics, comprising:

an acoustic-wave propagating medium;

a first transducer coupled to said medium, said first transducer including a first and a second group of electrodes, wherein said first and said second group of electrodes are interleaved;

a second transducer coupled to said medium for exchanging acoustic-wave signals with said first transducer, said second transducer including a third and a fourth group of electrodes which are substantially perpendicular to a first and second conducting region respectively, wherein said third and said fourth group of electrodes are interleaved, a plurality of said fourth group of electrodes having at least a coupled portion offset in alignment from another coupled portion; and

wherein adjacent electrodes in said first transducer are substantially identical in length, and wherein adjacent electrodes in said second transducer are substantially identical in length.

4. The electro-acoustic device of claim 3 wherein signals relating to the second group of electrodes having at least an offset coupled portion combine to produce a signal of preselected phase and amplitude.

5. The electro-acoustic device of claim 3 wherein said first transducer includes a first section and a second symmetrically located with respect to said second transducer, one electrode of said second group of electrodes displaced from a preselected distance toward said first section, a second of said group of electrodes equally displaced from a distance equal to said preselected distance away from said second section.

6. In a surface wave device of the type including a transducer with interleaved electrodes, an improved method of encoding said surface wave transducer with preestablished frequency characteristics, the interleaved electrodes being substantially perpendicular to a conducting bus bar region, wherein the improvement comprising the steps of:

a. determining relative locations of transducer electrodes and overlap amplitudes for adjacent transducer electrodes from a time domain representation of said preestablished frequency characteristics;

b. dividing a plurality of said electrodes into coupled electrode sections;

c. positioning said coupled electrode sections on a surfacewave propagating material about said determined electrode locations, said coupled electrode sections positioned to provide a combined signal amplitude related to an overlap amplitude for a corresponding electrode section; and

d. positioning undivided electrodes on said surface wave propagating material at said determined locations.

7. In a surface wave device including transducers with interleaved electrodes which are substantially perpendicular to a conducting bus bar region, an improved method of phase-encoding said surface wave device with preestablishing frequency characteristics, wherein the improvement comprises the steps of:

a. determining relative location of transducer electrodes and overlap amplitudes for adjacent transducer electrodes from a time domain representation of said preestablished frequency characteristics;

b. positioning at least a portion of a plurality of said electrodes on a surface-wave propagating material displaced from said electrode relative location, said positioning of said electrodes resulting in a signal determined by said overlap amplitude; and

c. positioning undisplaced electrodes at said determined relative locations.

8. The electro-acoustic transducer of claim 7 wherein each electrode extends substantially a predetermined distance along an adjacent electrode.

9. An electro-acoustic transducer for providing preestablished frequency characteristics;

comprising

an acoustic-wave propagating medium;

a first group of electrodes coupled to said medium and being substantially perpendicular to a first conducting region;

a second group of electrodes coupled to said medium and being substantially perpendicular to a second conducting region, wherein said second group of electrodes interleaves with said first group of electrodes, a portion of a plurality of electrodes from said first and said second group displaced from positions determined by a time domain representation of said preestablished frequency characteristics.

10. An electro-acoustic device for providing preestablished frequency characteristics comprising:

an acoustic-wave propagating medium;

a first group of electrodes coupled to said medium;

a second group of electrodes coupled to said medium wherein said first and said second group of electrodes are interleaved;

a third group of electrodes coupled to said medium and being substantially perpendicular to a first conducting region;

a fourth group of electrodes coupled to said medium and being substantially perpendicular to a second conducting region, wherein said third and said fourth group of electrodes are interleaved, wherein said third and said fourth group of electrodes are disposed to receive acoustic waves propagated by said first and said second group of electrodes, wherein at least a portion of each of a plurality of electrodes of said third and said fourth group are displaced from preselected positions by predetermined amount whereby the vector addition of signals generated by the third and fourth group of electrodes provide the preestablished frequency characteristics.

11. The electro-acoustic device of claim 10 wherein said predetermined amount is chosen to provide a desired amplitude.

12. The electro-acoustic device of claim 10 wherein said preselected positions and a desired amplitude are derived from a time-domain representation of said preestablished frequency characteristics.

13. The electro-acoustic device of claim 11 wherein an amount of overlap between adjacent electrodes of said third and said fourth group is substantially constant.

14. An electro-acoustic device having encoding of preestablished frequency characteristic, comprising:

a first group of electrodes;

a second group of electrodes, wherein said second group of electrodes is interleaved with said first group of electrodes, said first group of electrodes including a first plurality of sets of portions of electrodes, individual signals generated by each of said sets producing a preselected combined signal;

said first and second group of electrodes being substantially perpendicular to a first and second conducting region respectively;

an acoustic-wave propagating medium, said first and said second group of electrodes being coupled to said medium; and

wherein said preselected combined signal is determined by a time-domain representation of said preestablished frequency characteristics.

15. An electro-acoustic device having preestablished frequency characteristics, said preestablished frequency characteristics specifying preestablished signal phases and preestablished amplitudes, comprising:

an acoustic wave propagating medium;

a first transducer coupled to said medium, said first transducer including a first plurality of interleaved electrodes substantially perpendicular to a first conducting region;

a second transducer coupled to said medium, said second transducer including a second plurality of electrodes substantially perpendicular to a second conducting region, said second plurality of electrodes interleaved with said first plurality of electrodes wherein said second transducer produces output electrical signals in response to acoustic waves, said acoustic wave generated by input electrical signals to said first transducer, wherein electrodes in a plurality of sets of electrodes located in at least one of said first transducer and said second transducer produces signals having an amplitude intermediate to an amplitude produced by other electrodes combined intermediate signals of each set producing a composite signal having a phase and amplitude determined by said preestablished frequency characteristics.

16. An electro-acoustic device for providing predetermined frequency characteristics, comprising:

an acoustic-wave propagating medium;

a first electro-acoustic transducer mechanically coupled to said medium; and

a second electro-acoustic transducer mechanically coupled to said medium, said second transducer including a multiplicity of interleaved electrodes substantially perpendicular to a conducting region, a plurality of said electrodes having a first portion and a second portion, wherein said first and second portions of electrodes of each group are positioned to produce a composite electrical signal of amplitude and time delay at said first transducer determined by said predetermined frequency characteristics upon electrical excitation of said each group.

17. The electro-acoustic device of claim 16 wherein adjacent interleaved electrodes have a substantially constant overlap amplitude.

18. An electro-acoustic device for providing predetermined frequency characteristics comprising:

an acoustic-wave propagating medium;

an electro-acoustic transducer mechanically coupled to said medium, said transducer including a multiplicity of interleaved electrodes, a plurality of said electrodes having a first portion and a second portion said electrodes arranged to respond to passage of a selected acoustic wave by generating a combined electrical signal of determined amplitude and phase having said predetermined frequency characteristics; and

wherein said combined signal of determined amplitude and phase corresponds to a time domain representation of said predetermined frequency characteristics.