| 摘要 |
<p>A portal for automatically exciting and reading a passive transponder type tag, which is excited by an inductively coupled signal of a first predetermined frequency and which simultaneously produces a magnetic field and an electrostatic field modulated with a digitally coded identifying signal, while the tag is moving along a substantially horizontal conveyor belt. The portal comprises: a rectangular frame for placement around a portion of a substantially horizontal conveyor belt in a direction transverse to the direction of movement of the conveyor belt; first, second, third and fourth exciter coils, mounted respectively on an upper, a lower and respective side panels forming the walls of the frame, for producing a magnetic field of the first predetermined frequency within the interior of the frame; a curtain formed of a plurality of spaced flexible rectangular flaps of non-conductive material which are suspended from the upper panel within the frame, extend in a direction transverse to the direction of movement of the conveyor belt, and are of a length such that at least one flap will be contacted and deflected by an object moving along the conveyor belt; a pickup coil, serving as a magnetic field receiving antenna, and an electrostatic field receiving antenna disposed in each flap; and a receiver circuit, connected to each of the magnetic pickup coils and the electrostatic field receiving antennas, for detecting a coded signal of the second frequency received by any of the pickup coils and the electrostatic field receiving antennas.</p> |
