High bulk mode rejection surface wave device

• US 3,936,774 A
• Filed: 03/14/1974
• Issued: 02/03/1976
• Est. Priority Date: 03/14/1974
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Kempf, Richard Alan, Mellon, Donald Williams
• Primary Examiner(s): Borchelt, Archie R.
• Assistant Examiner(s): Nussbaum, Marvin
• Application Number:
  US05/450,966
• Time in Patent Office: 691 Days
• Field of Search: 333/30 R, 333/72, 29/25.35
• US Class Current: 333/151
• CPC Class Codes: G10K 11/36 Devices for manipulating acoustic surface waves electro-acoustic amplifiers H03F13/00; networks comprising electro-acoustic elements H03H9/00
• CPC Class Codes: H03H 9/02866 of bulk wave excitation and reflections
• CPC Class Codes: H03H 9/14517 Means for weighting
• CPC Class Codes: H03H 9/14544 Transducers of particular shape or position weighting H03H9/14517
• CPC Class Codes: H03H 9/14555 Chirped transducers H03H9/6406 takes precedence

Abstract

Disclosed is a surface wave device comprising one transducer having its fundamental resonant frequency at a subharmonic of the device operating frequency and a second transducer having its fundamental resonant frequency at the device operating frequency. Both transducers respond to surface waves at the operating frequency. Only the harmonic operated transducer responds to bulk waves at the operating frequency. Thus, signal coupled from one transducer to the other at the operating frequency contains no noise generated by bulk mode coupling.

Claims

1. A surface wave device having substantially no bulk mode signal output comprising:

a. a substrate for conveying acoustic waves;

b. a first transducer having a plurality of electrodes in operative association with the substrate for generating acoustic surface waves, each of said plurality of electrodes having a preselected spacing as to an adjacent electrode at one-half wavelength at a desired operating frequency to reduce substantially the response of the first transducer to bulk waves at the operating frequency; and

c. a second transducer having a plurality of electrodes in operative association with the substrate for receiving the first transducer output, each of said plurality of electrodes having preselected spacings from an adjacent electrode at one-half wavelength of a preselected subharmonic of said operating frequency.

2. A surface wave device according to claim 1 wherein said first surface wave transducer is an input surface wave transducer and said second surface wave transducer is an output surface wave transducer.

3. A surface wave device according to claim 2 wherein said input surface wave transducer comprises electrodes having widths of one quarter of the surface wavelength at the operating frequency.

4. A surface wave device according to claim 2 wherein said output surface wave transducer has a fundamental resonant frequency of one-third the preselected operating frequency.

5. A surface wave device according to claim 4 wherein said output surface wave transducer comprises electrodes having widths of four-tenths of the surface wavelengths at one-third the operating frequency, whereby third harmonic response is enhanced.

6. A method for fabricating surface wave devices for substantially rejecting bulk mode signals comprising:

a. forming electrodes with preselected spacings for an input surface wave transducer on a piezoelectric substrate for substantially reducing the response including bulk wave signal response of the transducer to a desired harmonic as to a fundamental resonant frequency; and

b. forming electrodes with preselected spacings for an output transducer for covering a subharmonic of said fundamental resonant frequency;

whereby said transducers cooperate during operation to reject bulk wave signals at the desired harmonic and fundamental resonant frequency.