Patent EA-001127-B1 (EA)
Title: Data exchange system by contactless communication between a terminal and remote powered portable objects
Inventor: WEHOVSKI FREDERIC
IPC: G07C9/00
Filed: 1997-12-08
Abstract: 1. A data exchange system comprising at least one terminal and a plurality of portable objects for co-operating with a terminal by contactless communication comprising a terminal (100), comprising  a coil (102) for emitting magnetic field, a means for transmitting data co-operating with said coil and comprising a means (108) for generating a variable signal and a means (110) of amplitude modulation, and a means (118, 116) for receiving data co-operating with said coil, a portable object (200), having an electrical circuit , which is remote recorded by the terminal, and comprising  a coil (202) for reading modulated magnetic field from the terminal and for producing a response by a modulated perturbation of the magnetic field, a converting means, co-operating with the coil of the portable object for converting read magnetic field into a direct voltage supply "d" to power the object circuit, whereby said means comprises a rectifying stage (210) and a filtering stage (212) and data transmitting and a means for data receiving means, also co-operating with coil of the portable object, whereby the means for receiving data comprises a means (218) for demodulation of the signal amplitude, read by the coil, whereby said means (218) of the amplitude demodulation operates on the signal "b" delivered in output of the rectifying and filtering stages, characterized in that the coils (102, 202) each form part of tuned resonant circuit (106, 208) radiating the field in free space, whereby the amplitude modulation radiated by the terminal, is a slight depth modulation, with a modulation rate typically equal or not more than 50%. 2. The system according to claim 1, characterized in that the modulation rate is below 20%. 3. A portable object (200) for contactless communication with the terminal, comprising a remote powered electronic circuit, which comprises a coil (202) for reading modulated magnetic field from the terminal and for producing a response by a modulated perturbation of the magnetic field, a converting means, co-operating with the coil of the portable object for converting read magnetic field into a direct voltage supply "d" to power the object circuit, whereby said means comprises a rectifying stage (210) and a filtering stage (212) and data transmitting and a means for data receiving means, also co-operating with coil of the portable object, whereby the means for receiving data comprises a means (218) for demodulation of the signal amplitude, read by the coil, whereby said means (218) of the amplitude demodulation operates on the signal "b" delivered in output of the rectifying and filtering stages, characterized in that the coil (202) forms part of tuned resonant circuit (106, 208) radiating the field in free space. 4. The portable object according to claim 3, characterized in that the means of the amplitude modulation  is means (244, 246, 248) with a variable threshold, comparing an instant signal value transmitted to their input, with the mean value of said signal. 5. The portable object according to claim 3 or 4, characterized in that the means of the amplitude modulation  is means (244, 250, 252, 260-268) sensible to the velocity, by which the instant value of the applied signal is increased. 6. The portable object according to claim 3, 4 or 5, characterized in that the converting means further comprises down the rectifying stage (210) and the filtering stage (212) the stabilizing shunt element (228) mounted in parallel with the circuit between its power supply outputs and associated with resistive element, connected in series in the busbar of the circuit, whereby the shunt stabilizing element is mounted for tapping changeable part of the feeding current for the circuit so that the resistive element and the shunt stabilizing element disperse any excessive energy, which is not required for circuit operation, wherein the voltage supply "d" is stabilized on the outputs of the circuit, the voltage supply "a" is limited on the outputs of the tuned element which is up along the circuit and the influence of the current consumption changes up the circuit for the amplitude of the demodulating signal is prevented. 7. The portable object according to any claim 3 to 6, characterized in that comprises a means (240) for selective and temporary inhibition of the shunt stabilizer operation. 8. The portable object according to claim 7, characterized in that comprises a means for detecting the type of communication - contactless or via contacts, whereby the selective and temporary inhibition of the shunt stabilizer operation is performed in response to the detection of the type of communication via contacts. 9. The portable object according to any claim 3 to 6, characterized in that the electronic circuit (202,204), except for the coil (202) of the tuned element, is realized by the technology of monolithic integral circuits. 10. The portable object according to any claim 3 to 9, characterized in that the means for data transmitting is a means (222), which operated by modulating of current consumption down the circuit from the tuned element, whereby the system is designed foe operation in two modes of the power consumption - with rated consumption and low consumption, and comprises a means for transferring the system into low consumption mode before the means for data transmitting starts modulating. 11. The terminal for contactless communication with a portable object, remote powered terminal, comprising a coil (102) for radiating magnetic field, a means for transmitting data co-operating with said coil and comprising a means (108) for generating a variable signal and a means (110) of amplitude modulation, and a means (118,116) for receiving data co-operating with said coil, characterized in that the coil is a part of that the of tuned resonant circuit (106,) radiating the field in free space, whereby the amplitude modulation radiated by the terminal, is a slight depth modulation, with a modulation rate typically equal or not more than 50%. 12.The terminal according to claim 11, characterized in that the modulation rate is below 20%.