A system for exchanging data by communication via contacts or without contact between a terminal and portable objects

摘要

The terminal includes a coil co-operating with a data transmitter/receiver. The portable object includes a remotely powered electric circuit including: a coil for picking up the modulated magnetic field from the terminal or for responding by producing modulated disturbance of the magnetic field; a converter including a rectifier stage and a filter stage transforming the magnetic field picked up by the coil into a DC power supply voltage; and a data transmitter/receiver, the receiver including a demodulator for demodulating the amplitude of the signal picked up by the coil, the amplitude demodulator operating on the signal output by the rectifier and filter stages. Each of the coils forms a portion of a tuned resonant circuit radiating the field in free space. The amplitude modulation is a low depth modulation, with a modulation ratio that is typically less than or equal to 50%.