Title: Multiple loop antenna
Application Number: 98801830 Application Date: 1998.01.12
Publication Number: 1243609 Publication Date: 2000.02.02
Approval Pub. Date: 2004.01.28 Granted Pub. Date: 2004.01.28
International Classifi-cation: G08B13/14;H01Q11/12
Applicant(s) Name: Checkpoint Systems, Inc. Address:
Inventor(s) Name: John H. Bowers;Wu Wen-Liang
Attorney & Agent: jian wei
Abstract:
    A multiple loop antenna (30) is provided which may be connected to either a transmit circuit (64), a receive circuit, or a transmit/receive circuit. When powered by the transmit circuit, the antenna generates radio frequency magnetic fields in an area or zone proximate to the antenna, but which are substantially canceled at a distance approximately one wavelength and more from the antenna, thereby defining a surveillance zone proximate to the antenna. Radiating loop segments (36, 38) of the antenna are centered around a common feed point and are geometrically symmetrical, such that currents are precisely controlled in each loop segment.
Time: 5