IDENTIFICATION SYSTEM

摘要

An object identification system has a transmitter (8) supplying a signal (M13) from an inductor (3) of a transmitter (8) by low loss near-field coupling to an inductor (1) of a transponder (5) on the object to be identified. The energy of this signal (M13) is stored in a capacitor (6) and re-radiated by the inductor (1), at a reduced frequency formed in effect by cancellation of part of the incoming wave, to an inductor (2) of a receiver (7) as a reply signal (M12). The reduction in frequency is achieved by a switching system in the transponder (5) which is controlled by a control signal (P1) from a control circuit (4). This control circuit may be powered by energy (P2) from the inductor (1). The switching is performed by a FET (TR1) and occurs at suitable points in the operating cycle to ensure the minimum energy loss. The operation of switching is coded in code generator (20) to produce a desired reply signal (M12) carrying information about the object to be identified.