Inductive device for the rapid exchange of data between two data carriers

Claim 1

A device for the rapid exchange of data between a reading-writing station and a movable data carrier by the inductive transmission of logic signals, said readingwriting station comprises : i-a capacitor connected to one common emitting-receiving coil which is wound on a high permeability ferrite bar of a magnetic circuit and which can be magnetically coupled to a corresponding coil of the data carrier, said capacitor and said coil forming a part of a resonating circuit which can be tuned to a frequency ; ii-an emitting circuit and a receiving circuit, both connected to the said common coil, the emitting circuit comprising means for transmitting to said common coil a high frequency current which can be modulated by said signals and the receiving circuit comprising means for receiving a high frequency current induced in the common coil by a high frequency magnetic field generated by said corresponding coil ; iii-an automatic tuning circuit for maintaining the frequency of the resonating circuit at a nominal value, said automatic tuning circuit comprising a comparator means which compares a signal representative of the frequency of the resonating circuit with a reference value and which delivers an error signal corresponding to a difference between the said frequency and the said nominal value, a tuning means including a tuning coil acting on the said magnetic circuit and means for energizing the tuning coil by a DC current having a value which varies as a function of the error signal, so as to generate a corrective magnetic field in the magnetic circuit which causes the said frequency to be stabilized to the nominal value.

Claim 2

A device for the rapid exchange of data between a reading-writing station and a movable data carrier by the inductive transmission of logic signals, said readingwriting station comprises : i-a capacitor connected to one common emitting-receiving coil which is wound on a high permeability ferrite bar of a magnetic circuit and which can be magnetically coupled to a corresponding coil of the data carrier, said capacitor and said coil forming a part of a resonating circuit which can be tuned to a frequency ; ii-an emitting circuit and a receiving circuit, both connected to the said common coil, the emitting circuit comprising means for transmitting to said common coil a high frequency current which can be modulated by said signals and the receiving circuit comprising means for receiving a high frequency current induced in the common coil by a high frequency magnetic field generated by said corresponding coil ; iii-an automatic tuning circuit for maintaining the frequency of the resonating circuit at a nominal value, said automatic tuning circuit comprising a comparator means which compares a signal representative of the frequency of the resonating circuit with a reference value and which delivers an error signal corresponding to a difference between the said frequency and the said nominal value, a tuning means including a tuning coil acting on the said magnetic circuit and means for energizing the tuning coil by a DC current having a value which varies as a function of the error signal, so as to generate a corrective magnetic field in the magnetic circuit which causes the said frequency to be stabilized to the nominal value.