Surface acoustic wave passive transponder having non-reflective transducers and pads

• US 4,604,623 A
• Filed: 06/30/1983
• Issued: 08/05/1986
• Est. Priority Date: 06/30/1983
• Status: Expired due to Term

• Current Assignee: X-Cyte Inc.
• Original Assignee: X-Cyte Inc.
• Inventors: Skeie, Halvor
• Primary Examiner(s): Tubbesing, T. H.
• Assistant Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US06/509,524
• Time in Patent Office: 1,132 Days
• Field of Search: 343/6.5 SS, 343/6.8 R, 343/6.8 LC, 310/313 R, 310/313 B, 310/313 D, 333/150-155, 333/193-196
• US Class Current: 342/51
• CPC Class Codes: G01S 13/343 using sawtooth modulation
• CPC Class Codes: G01S 13/755 using delay lines, e.g. acoustic delay lines
• CPC Class Codes: G06K 19/0675 the resonating marks being of the surface acoustic wave [SAW] kind SAW devices per se H03H9/64

Abstract

A passive transponder for use in an interrogation/transponder system comprises a substrate having a substrate surface defining a path of travel for surface acoustic waves; a launch transducer element arranged on the surface for converting interrogating signals into surface acoustic waves which propagate along the path of travel; a plurality of tap transducer elements arranged on the surface at spaced intervals along the path of travel for converting surface acoustic waves into respective output signals; and a circuit, connected to the tap transducer elements, for combining the output signals of these transducer elements to form reply signals. In order to minimize reflections from the edges of the transducer elements, these elements are configured with serrated edges facing the path of travel.

Claims

1. In a passive transponder adapted for use in an interrogation system for transmitting a reply signal containing coded information in response to the receipt of an interrogating signal, said transponder comprising:

(a) a substrate having a substrate surface defining a plurality of paths of travel for surface acoustic waves, each path of travel having a different length from its beginning to its end; and

(b) electric circuit means for propagating surface acoustic waves along said paths of travel, from said beginning of each path to said end thereof, said electric circuit means comprising a plurality of metallized layer elements, disposed on said substrate and arranged in said paths of travel;

the improvement wherein at least one of said layer elements has a substantially linear serrated edge on a side thereof facing a path of travel to reduce acoustic wave reflections from said edge, the width of the serration in said serrated edge in the direction of said path of travel being substantially equal to nλ

/4, where n is an odd integer and λ

is the center wavelength of said surface acoustic waves.

3. The improvement defined in either claim 1 or claim 2, wherein a serrated edge is provided on both sides of said element.

4. The improvement defined in claim 1 or claim 2, wherein a serrated edge is provided on all of said elements arranged in said paths of travel.

6. The improvement defined in claim 1 wherein the serrations of said serrated edge are "T" shaped.

7. The improvement defined in claim 1, wherein the serrations of said serrated edge are "L" shaped.

8. The improvement defined in claim 1, wherein said one layer element having a serrated edge is a tap transducer.

2. In a passive transponder adapted for use in an interrogation system for transmitting a reply signal containing coded information in response to the receipt of an interrogating signal, said transponder comprising:

(a) a substrate having a substrate surface defining a plurality of paths of travel for surface acoustic waves, each path of travel having a different length from its beginning to its end;

(b) electric circuit means for propagating surface acoustic waves along said paths of travel, from said beginning of each path to said end thereof; and

(c) a plurality of surface acoustic wave delay pad elements disposed on said substrate and arranged in said paths of travel to control the surface acoustic wave propagation time;

the improvement wherein at least one of said delay pad elements has a substantially linear serrated edge on a side thereof facing a path of travel to reduce acoustic wave reflections from said edge, the width of the serration in said serrated edge in the direction of said path of travel being substantially equal to nλ

/4, where n is an odd integer and λ

is the center wavelength of said surface acoustic waves.

5. The improvement defined in claim 2, wherein the serrations of said serrated edge are rectangular in shape.