(12) United States Patent ao) Patent No.: us 6,744,367 Bi
Forster (45) Date of Patent: Jun. 1,2004
(54) IDENTIFICATION TAG
(75) Inventor: Ian Forster, Chelmsford (GB)
(73) Assignee: Marconi Data Systems Limited,
Hatfield (GB)
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.
(21) Appl. No.: 09/979,191
(22) PCT Filed: May 15, 2000
(86) PCT No.: PCT/GB00/01878
§ 371 (c)(1),
(2), (4) Date: Mar. 12, 2002
(87) PCT Pub. No.: WO00/72255 PCT Pub. Date: Nov. 30, 2000
(30) Foreign Application Priority Data
May 22, 1999 (GB) 9911878
(51) Int. CI.7 G08B 13/14
(52) U.S. CI 340/572.7; 340/5.8; 340/572.4;
340/870.02; 340/870.18; 310/313 R; 310/322;
310/367
(58) Field of Search 340/572.7, 572.4,
340/572.5, 5.8, 870.18, 870.02; 310/367, 313 R, 181, 322; 235/492
(56) References Cited
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4,676,104 A * 6/1987 Cullen 73/516 R
4,951,057 A * 8/1990 Nagel 342/51
4,980,680 A * 12/1990 Knoll et al 340/825.31
5,469,170 A 11/1995 Mariani
5,517,195 A 5/1996 Narlow et al.
5,734,332 A 3/1998 Kirknes
6,060,815 A * 5/2000 Nysen 310/318
6,104,311 A * 8/2000 Lastinger 340/825.54
6,330,939 Bl * 12/2001 Pratt 194/206
FOREIGN PATENT DOCUMENTS
EP 0 142 380 A2 5/1985
EP 0 413 634 A2 2/1991
GB 1 433 140 4/1976
GB 1 534 750 12/1978
GB 2 139 956 A 11/1984
GB 2 306 080 A 4/1997
* cited by examiner
Primary Examiner—Daniel J. Wu
Assistant Examiner—Son Tang
(74) Attorney, Agent, or Firm—Kirschstein, et al.
(57) ABSTRACT
An identification tag is provided comprising a multilayer assembly incorporating, in sequence, a metal backing layer, a bulk structural layer, a piezo-electric layer and an electrode layer. The electrode layer incorporates antennas structures for receiving interrogating radiation comprising a first radiation component at a relatively lower frequency and a second radiation component at a relatively higher frequency. The electrode layer also incorporates a structure for modulating a second signal generated in response to receiving the second component by a first signal generated in response to receiving the first component to generate a modulated signal which is re-emitted as reflected radiation from the tag. The presence of the tag is determinable from modulation components present in the reflected radiation, thereby distinguishing the tag from other objects capable of reflecting radiation, but not modulating it.
22 Claims, 4 Drawing Sheets
