ACOUSTIC SURFACE WAVE FILTER

• US 3,600,710 A
• Filed: 08/12/1968
• Issued: 08/17/1971
• Est. Priority Date: 08/12/1968
• Status: Expired due to Term

• Current Assignee: Adrian J De Vries, Robert Adler
• Original Assignee: Adrian J De Vries, Robert Adler
• Inventors: Adler, Robert, De Vries, Adrian J.
• Primary Examiner(s): Saalbach, Herman Karl
• Assistant Examiner(s): Baraff, C.
• Application Number:
  US04/752,073
• Time in Patent Office: 1,100 Days
• Field of Search: 333/30,72 310/8 330/5.5 343/17.2 340/10
• US Class Current: 333/193
• CPC Class Codes: H03H 9/1455 constituted of N parallel or series transducers
• CPC Class Codes: H03H 9/14597 Matching SAW transducers to external electrical circuits

Abstract

A body of piezoelectric material propagates acoustic surface waves. A first surface wave interaction device is actively coupled to that surface to interact with the waves. Spaced on the same surface from the first device is a second such interaction device. The interaction devices are segmented into a plurality of interjacent arrays of electrode elements and the spacing between successive electrode elements is equal to an integral multiple of one-half wavelength at the desired operating frequency. The arrays are electrically coupled in series and are disposed to effect cumulative interaction with the surface waves.

Claims

1. In an acoustic wave filter including a body of piezoelectric material propagative of acoustic waves along a surface thereof and having a surface wave interaction arrangement actively coupled to said surface, the improvement in which:

said surface wave interaction arrangement has an input terminal and an output terminal and a plurality of similar surface wave interaction devices, which individually have an array of interleaved electrode elements with the spacing between successive elements equal to an integral number of one-half wavelength at the desired operating frequency, which are electrically coupled in series between said input and output terminals, which are disposed to effect cumulative interaction with said surface waves nd which present across said input and output terminals in an impedance equal to N2Z, where N is the number of said devices in said plurality and Z is the individual impedance of said devices.

2. A filter as defined in claim 1 in which said arrays are disposed to interact with individual acoustic wave trains propagating along a common path.

3. A filter as defined in claim 1 in which said devices are disposed to interact with individual acoustic wave trains propagating along a common path and in which each of said arrays includes an odd number of said electrode elements.

4. A filter as defined in claim 1 in which said devices are disposed to interact with individual acoustic waves trains propagating along a common path and in which each of said arrays includes an even number of said electrode elements.

5. In an acoustic wave filter including a body of piezoelectric material propagative of acoustic waVes along a surface thereof and having a surface wave interaction arrangement actively coupled to said surface, the improvement comprising:

said surface wave interaction arrangement has an input terminal and an output terminal and a plurality of surface wave interaction devices having electrode arrays electrically coupled in combination and disposed to effect cumulative interaction with said surface waves, each of said arrays being composed of interleaved combs of conductive electrodes with the spacing between adjacent teeth of said combs being substantially one-half the wavelength of said waves; and

one of the combs in at least one of said arrays having a spine in common with that of one of the combs of an adjacent array.

6. A filter as defined in claim 5 in which said arrays are coupled in parallel combination.