| 摘要 |
In an electronic article surveillance system (24), quadrature transmitting a nd receiving antennas are used to improve field distribution. A transmitting antenna arrangement includes first and second adjacent co- planar antenna loops (42, 44) and excitation circuitry (46) for generating respective alternating currents in the first and second loops suc h that the respective alternating currents are 90.degree. out of phase. In a receiving arrangement (300), respective signals received from two adjacent c o- planar antenna loops (302, 304) are respectively phase-shifted by +45.degree. and -45.degree. and the resulting phase-shifted signals are summed. A far-field canceling transmitting antenna arrangement includes four loops (66', 78, 68, 70) operated at phases of 0.degree., 90.degree., 180.degree. and 270.degree. respectively. All four loops may be co-planar, with any bucking vertical segments being horizontally displaced from each other. Alternativel y, the 0.degree. and 180.degree. loops may also be arranged in a common plane that is close to and parallel with another plane in which the 90.degre e. and 270.degree. loops are arranged.
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