Communications: electrical – Continuously variable indicating – With meter reading
Patent
1998-01-26
2000-01-04
Horabik, Michael
Communications: electrical
Continuously variable indicating
With meter reading
34082534, 34082531, 3405721, 3405724, 342 44, 343895, 343867, G08B 1314
Patent
active
060114886
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a radio frequency interface device for a transponder, and in particular the voltage converting circuit of such an interface.
The invention is particularly suitable for the radio frequency interface of a transponder used as a contactless identification device.
A device of this type comprises an electromagnetic antenna in the form of an inductive coil of very small dimensions, connected as input/output to an integrated circuit via a voltage converting circuit, providing the continuous voltage supply of the integrated circuit.
Transponders of this type do not have a battery and are intended to exchange information with an interrogation device or an identification device with which they are connected in a wireless manner. The voltage supply which the transponder needs to function is consequently obtained from a radio frequency excitation signal emitted by the interrogation device. This radio frequency signal is rectified in the transponder and the voltage thus produced is used to charge a capacitor forming means for stocking energy. The energy thus stocked is used by the circuits of the transponder for writing information in the logic circuits, in particular the memories, and for modulating a response radio frequency signal intended for the interrogation device when it is reading the transponder.
Such a transponder device is described in the document U.S. Pat. No. 4,196,418. This device comprises to this effect a rectifying circuit allowing to rectify and thus to use the resonance circuit voltage to supply the different components of the device.
Such transponders can be used practically in a large variety of applications, in particular for the identification of objects which are at a distance.
In this context, one of the problems posed resides in the fact that the input voltage of the interface of the transponder determines the limitation of the distance of functioning. i.e. the maximum distance between the emitter or the receiver of an electromagnetic signal and the transponder for allowing the exchange of information between the source and the transponder. To this effect, for increasing the operation distance, it is known in the state of the art to use a voltage doubler at the output of the rectifying circuit, but in such a case, the rectifying diodes of the interface might break down because of the too big inversed voltage caused by this doubler.
The present invention has as aim to remedy these inconveniences, and to propose an interface device capable of increasing the operation distance while thereby avoiding an important inversed tension to be applied to the rectifying diodes of the interface. Furthermore, the invention has as aim to propose a device allowing to incorporate standard protection circuits, this not being possible with a classic voltage doubler.
Another aim of the invention is to propose an interface for transponders capable of generating sufficient current so that the transponder can receive a microprocessor or other integrated circuits which have a relatively high current consumption, such as, in particular a non-volatile memory.
To this effect, the invention has as its object a radio frequency interface for a transponder, comprising a coil forming the antenna of the transponder and a voltage converting circuit connected to, on the one hand, the terminals of said coil and, on the other hand, continuous voltage supply terminals of an integrated logic circuit of the transponder, characterised in that the terminals of the coil are connected to floating potentials with respect to the substrate of the transponder, in such a way that none of the terminals of the coil have a potential which passes below the potential of the substrate, and in that said voltage converter is a voltage tripler which comprises a first rectifier connected to the terminals of the coil and which is constituted by a first diode connected in series with a first capacitor, a second rectifier connected to the terminals of the first diode and constituted by a second diode in series with a second
REFERENCES:
patent: 3478258 (1969-11-01), Nagai
patent: 4075632 (1978-02-01), Baldwin et al.
patent: 4196418 (1980-04-01), Kip et al.
patent: 5266926 (1993-11-01), Beigel
patent: 5559507 (1996-09-01), Beigel
Dalencourt Yves
EM Microelectronic-Marin SA
Horabik Michael
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