| 摘要 |
<p>This invention relates to dynamically controlled, electronic article surveillance (EAS) systems whereby an array of antenna elements (Ant. 1, Ant. 2,...) is digitally phased and actively driven for concurrent transmission, and digitally phased and combined in the receiver unit (24) to improve security tag detection. In particular, the individual frequency and phase of the plurality of the transmit/receive signals are rapidly varied to allow for automated manipulation (steering) of the transmit field pattern and receive field sensitivity. It is the object of this invention to achieve the following features via means of digital phasing and dynamic computer control: sufficient far-field cancellation, null-free detection and uncompromised detection performance regardless of tag's orientation.</p> |
