| 摘要 |
Logistical passage measurement systems are provided. A representative system includes: an excitation unit having dual loop antennae, with a first loop and a second loop, the two loops located in and parallel to the same plane, and adjacent to one another, and a control box for exciting said antennae, the control box arranged to drive the currents of the two loops, such that the phase difference between the currents of said two loops alternates with time between 0° and 180°, and wherein the amplitude of the currents for each loop is of a first level when the phase difference is 180° and wherein said amplitude is of a second level, lower than the first level, when the phase difference is 0°.
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