Identification mark operating with acoustic surface waves

• US 5,841,214 A
• Filed: 08/22/1996
• Issued: 11/24/1998
• Est. Priority Date: 02/22/1994
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Schmidt, Frank, Reindl, Leonhard, Ostertag, Thomas, Magori, Valentin
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US08/701,492
• Time in Patent Office: 824 Days
• Field of Search: 73/570, 342/42, 342/44, 342/51, 340/572, 340/825.34, 340/825.72, 310/313 B, 310/313 D, 333/150, 333/153, 333/154
• US Class Current: 310/313.00D
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• 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
• CPC Class Codes: G06K 7/10009 sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves

Abstract

An identification mark operating with acoustical surface waves includes at least one reflector having higher reflectivity than a reflectivity of other reflectors.

Claims

1. In an identification system having an identification mark or ID tag operating with acoustic surface waves, and an interrogation/evaluation unit interrogating the identification mark with a wirelessly transmitted interrogation signal and evaluating an encoded response signal sent back from the identification mark, the identification mark, comprising:

ID tag reflectors having a reflectivity and having a number and position defining an encoding of the response signal; and

at least one further reflector having greater reflectivity than the reflectivity of said reflectors defining the encoding, said at least one further reflector receiving an interrogation pulse and returning an echo pulse within an assigned time window for identifying a presence of the ID tag, said at least one further reflector responding to the interrogation pulse having an energy level below a threshold level of interrogation by said ID tag reflectors.

2. The identification mark according to claim 1, including an interdigital converter, said reflectors being disposed in a sequence, and said reflector having high reflectivity being the last reflector in said sequence as seen from said interdigital converter.

3. The identification mark according to claim 1, wherein said reflector having high reflectivity is a dispersive reflector, and said reflectors defining the code are reflectors reflecting in a linear phase.