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Antenna for RF tag with a magnetoelastic resonant core
| Details |
Inventors: Castellano, Anthony; Heinrich, Harley Kent; Schrott, Alejandro Gabriel; Von Gutfeld, Robert Jacob;
Assignee: Intermec IP Corp. (Woodland Hills, CA)
Primary Examiner: Lee; Benjamin C.
Assistant Examiner: Trieu; Van T.
Attorney, Agent or Firm: O'Melveny & Myers LLP
A radio frequency identification transponder (RFID tag) includes an RFID antenna and one or more elements of nonlinear magnetic material tuned to resonate at substantially the same frequency as the resonant frequency of the tag antenna. This co-resonance amplifies signals that impinge upon the antenna, yielding both a higher level signal from the antenna to the tag electronics and wider operational bandwidth for the tag. With the addition of the nonlinear magnetic material, the tag may also be employed as a magnetic surveillance tag, with the attendant non-screening capabilities. With a plurality of nonlinear magnetic elements tuned to different resonant frequencies, the tag may provide more "non-screenable" information, that is, two bits, or four binary states, for example, when two such elements are employed. |
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DETAILED DESCRIPTION A radio frequency identification transponder (RFID tag) in accordance with the principles of the present invention combines a tag antenna, one or more elements of nonlinear magnetic material, and RFID electronics.
The nonlinear magnetic material and antenna are situated to interact in a manner whereby the antenna's output signal to the tag electronics is increased in magnitude relative to the antenna's response without the nonlinear magnetic material.
Additionally, the bandwidth of the RFID tag is increased, and the nonlinear magnetic material may also be employed as a magnetic surveillance article.
An RFID tag which incorporates the functionality of RFID tags and magnetic surveillance tags is disclosed in U.
S.
patent application Ser.
09/071,413, filed May 1, 1998, which is hereby incorporated by reference in its entirety.
An RFID system in accordance with the principles of the present invention is illustrated in the conceptual block diagram of FIG.
1.
An RF base station 100 includes an RF transmitter 102, an RF receiver 104, and an antenna 106 connected to the transmitter 102 and receiver 104.
An RF tag 116 such as may be used in conjunction with the base station 100 includes an RF front end 110, a signal processing section 112, and an antenna 114 which receives electromagnetic signals transmitted from the base station and passes the signals along to RFID tag electronics which comprise the RF front end 110 and signal processing section 112.
In operation, the base station 100 interrogates the tag 116 by generating an RF signal having a carrier frequency F.
sub.
c.
The carrier frequency F.
sub.
c is chosen based on a number of factors known in the art, including the amount of power permitted at that frequency by FCC regulations.
The RF signal is coupled to the antenna 106 and transmitted to the tag 116.
The tag 116 may be employed in any of a number of inventory control or tracking applications.
In accordance with the principles of the invention, the tag 116 includes at least one element of nonlinear magnetic material that is situated to interact with the antenna to amplify signals received by the antenna
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Telecommunications 
