| 摘要 |
<p>A directional antenna configuration (52) for use in an article tracking sytem (50) includes two shorted loops (82, 82'), one on each side of a portal or doorway (68) and in each case circumscribing the portal. The antenna configuration also includes a respective pair of passage antennas (78, 80 and 78, 80') provided on each side of the portal. The passage antennas are all arranged in planes parallel to the path of travel (72) through the doorway. The respective loops confine the effective detection areas of each pair of passage antennas to the respective side of the portal. The antenna configuration permits reliable detection of direction of movement through the portal.</p> |
