Patent ID: 6014088
Filing Date: 2000-01-11
Classification: G06K

Abstract:
A system for contactless exchange of information by wireless radiofrequency signal transmission between a read/write unit and an information carrier, comprising:a read/write unit comprising a first input/output circuit, an associated first coil means, and a first processing circuit;said first input/output circuit comprising a radiofrequency oscillator, a first gate with inputs for an output of said radiofrequency oscillator and a data signal, said first gate being gated by the data signal;said first coil means being operatively connected to an output of said first gate for taking a radiofrequency signal;an information carrier comprising a second input/output circuit, an associated second coil means, and a second processing circuit;said first and second coil means being inductively coupled to each other for bidirectional data transmission when the information carrier is positioned within transmission range of the read/write unit;said information carrier second coil means, responsive to a transmission of the radiofrequency signal by the read/write unit, being variably tuned, solely during said radiofrequency signal being transmitted, for a data signal transmission, andsaid first processing means dividing the data signal transmission into time slots, each of which comprises a trailing edge sync pulse and a single data bit which is a one bit or a zero bit,wherein said first input/output circuit of said read/write unit further comprisesa rectification circuit for rectifying an input signal;a detector having two sample and hold circuits, connected in parallel, said detector being operatively connected to said rectification circuit for receiving and applying the rectified input signal in parallel to said sample and hold circuits, and operatively connected to receive first and second sampling pulses, from said first processing circuit, for sampling successively in time the input signal; andan analog-to-digital converter operatively connected to receive output signals of said two sample and hold circuits.