Source: http://www.google.com/patents/US6703921?dq=7,292,151
Timestamp: 2017-04-30 00:49:55
Document Index: 295254298

Matched Legal Cases: ['Application No. 00', 'Application No. 00', 'Application No. 00', 'Application No. 00', 'Application No. 00', 'Application No. 00', 'Application No. 00', 'Application No. 98', 'Application No. 98', 'Application No. 99', 'Application No. 99', 'Application No. 99', 'Application No. 99', 'Application No. 99', 'Application No. 99', 'Application No. 99', 'Application No. 99', 'Application No. 99']

Patent US6703921 - Operation in very close coupling of an electromagnetic transponder system - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA method and a system of data transmission between a terminal for generating an electromagnetic field and a transponder, the terminal and the transponder each including an oscillating circuit forming an antenna, and the transponder including an electronic circuit adapted to absorbing and giving back...http://www.google.com/patents/US6703921?utm_source=gb-gplus-sharePatent US6703921 - Operation in very close coupling of an electromagnetic transponder systemAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS6703921 B1Publication typeGrantApplication numberUS 09/543,278Publication dateMar 9, 2004Filing dateApr 5, 2000Priority dateApr 7, 1999Fee statusPaidAlso published asDE60040113D1, EP1045336A1, EP1045336B1Publication number09543278, 543278, US 6703921 B1, US 6703921B1, US-B1-6703921, US6703921 B1, US6703921B1InventorsLuc Wuidart, Michel Bardouillet, Jean-Pierre EnguentOriginal AssigneeStmicroelectronics S.A.Export CitationBiBTeX, EndNote, RefManPatent Citations (98), Non-Patent Citations (18), Referenced by (140), Classifications (14), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetOperation in very close coupling of an electromagnetic transponder system
US 6703921 B1Abstract
A method and a system of data transmission between a terminal for generating an electromagnetic field and a transponder, the terminal and the transponder each including an oscillating circuit forming an antenna, and the transponder including an electronic circuit adapted to absorbing and giving back power provided by the terminal field, the oscillating circuits of the transponder and of the terminal being capable of transmitting radio-electric signals of determined frequency, this method including causing a detuning of at least one of the oscillating circuits with respect to the determined frequency when the transponder and the terminal are very close to each other.
What is claimed is: 1. A method of data transmission between a terminal for generating an electromagnetic field and a transponder, the terminal and the transponder each including an oscillating circuit forming an antenna, and said transponder including an electronic circuit adapted to drain and give back power provided by the electromagnetic field from the terminal, the oscillating circuits of the transponder and of the terminal being capable of transmitting radio-electric signals of determined frequency, the method including causing a detuning of at least one of the oscillating circuits with respect to the determined frequency, so as to decrease a coupling coefficient between the oscillating circuits while maintaining communication between the transponder and the terminal, when the transponder and the terminal are very close to each other.
2. The method of claim 1, wherein the oscillating circuits are tuned when the transponder is further away from the terminal than a critical coupling position between the oscillating circuits, at least one of the circuits being detuned when the transponder is between the critical coupling position and the terminal.
3. The method of claim 2, wherein detuning is caused when respective antennas of the transponder and of the terminal are at less than two centimeters away from each other.
4. The method of claim 1, further including detuning both oscillating circuits.
5. The method of claim 1, further including modifying a data transmission rate from the transponder to the terminal and/or from the terminal to the transponder according to whether the oscillating circuits are or are not tuned to the determined frequency.
6. The method of claim 1, wherein said determined frequency corresponds to a frequency of a remote supply carrier of the transponder.
7. A system of wireless and contactless data transmission between a terminal that generates an electromagnetic field and at least one transponder having no independent supply means, at least one of the terminal and the transponder including means for implementing the method of claim 1.
8. A method for communication between a terminal and a remote transponder that receives operating power from the terminal, the method comprising acts of:
generating with the terminal an electromagnetic field; determining a distance between the terminal and the remote transponder; detuning an oscillating circuit of one of the terminal and the transponder, so as to decrease a coupling coefficient between the transponder and the terminal in a detuned state, in response to the distance between the terminal and the transponder being less than a predetermined value; wherein the transponder still receives operating power from the terminal in the detuned state. 9. The method of claim 8, wherein detuning the oscillating circuit includes an act of regulating a phase of a current through the oscillating circuit.
10. The method of claim 9, wherein regulating the phase of the current includes acts of:
measuring the phase of the current; and varying a capacitance of the oscillating circuit so as to achieve a desired phase of the current. 11. The method of claim 10, wherein measuring the phase of the current includes acts of:
measuring the current with a current-measuring device to provide a measured current; comparing a phase of the measured current with a phase of a reference signal using a phase comparator; and determining the phase of the current based on the comparing act. 12. The method of claim 8, wherein determining the distance includes acts of:
measuring a first voltage when the oscillating circuit is in a tuned mode; measuring a second voltage when the oscillating circuit is in the detuned mode; comparing the first and second voltages to provide a comparison bit; and determining the distance between the terminal and the transponder, relative to a critical coupling point, based on a value of the comparison bit. 13. The method of claim 8, further comprising an act of varying a rate of data transmission between the terminal and the remote transponder based at least in part on the distance between the terminal and the remote transponder.
The present invention relates to systems using electromagnetic transponders, that is, transceivers (generally mobile) capable of being interrogated in a contactless and wireless manner by a unit (generally fixed), called a read/write terminal. The present invention more specifically relates to transponders having no independent power supply. Such transponders extract the power supply required by the electronic circuits included therein from the high frequency field radiated by an antenna of the read/write terminal. The present invention applies to such transponders, be they read only transponders, that is, adapted to operating with a terminal only reading the transponder data, or read/write transponders, which contain data that can be modified by the terminal.
Electromagnetic transponders are based on the use of oscillating circuits including a winding forming an antenna, on the transponder side and on the read/write terminal side. These circuits are intended to be coupled by a close magnetic field when the transponder enters the field of the read/write terminal. The range of a transponder system, that is, the maximum distance from the terminal at which a transponder is activated (awake) depends, especially, on the size of the transponder antenna, on the excitation frequency of the coil of the oscillating circuit generating the magnetic field, on the intensity of this excitation, and on the transponder power consumption.
Generally, unit 1 is essentially formed of an oscillating circuit formed of an inductance L1 in series with a capacitor C1 and a resistor R1, between an output terminal 2p of an amplifier or antenna coupler 3 (DRIV) and a terminal 2m at a reference potential (generally, the ground). Amplifier 3 receives a high-frequency transmission signal Tx, provided by a modulator 4 (MOD). The modulator receives a reference frequency, for example, from a quartz oscillator 5 and, if necessary, a data signal to be transmitted. In the absence of a data transmission from terminal 1 to transponder 10, signal Tx is used only as a power source to activate the transponder if said transponder enters the field. The data to be transmitted come from an electronic system, generally digital, for example, a microprocessor 6 (μP).
On the side of transponder 10, an inductance L2, in parallel with a capacitor C2, forms a parallel oscillating circuit (called a reception resonant circuit) intended for capturing the field generated by series oscillating circuit L1C1 of terminal 1. The resonant circuit (L2, C2) of transponder 10 is tuned on the frequency of the oscillating circuit (L1, C1) of terminal 1.
Terminals 11, 12 of resonant circuit L2C2, which correspond to the terminals of capacitor C2, are connected to two A.C. input terminals of a rectifying bridge 13 formed, for example, of four diodes D1, D2, D3, D4. In the representation of FIG. 1, the anode of diode D1 and the cathode of diode D3 are connected to terminal I1. The anode of diode D2 and the cathode of diode D4 are connected to terminal 12. The cathodes of diodes D1 and D2 form a positive rectified output terminal 14. The anodes of diodes D3 and D4 form a reference terminal 15 of the rectified voltage. A capacitor Ca is connected to rectified output terminals 14, 15 of bridge 13 to store power and smooth the rectified voltage provided by the bridge. It should be noted that the diode bridge may be replaced with a single-halfwave rectifying assembly.
When transponder 10 is in the field of terminal 1, a high frequency voltage is generated across resonant circuit L2C2. This voltage, rectified by bridge 13 and smoothed by capacitor Ca, provides a supply voltage to electronic circuits of the transponder via a voltage regulator 16 (REG). These circuits generally include, essentially, a microprocessor (μP) 17 (associated with a memory not shown), a demodulator 18 (DEM) of the signals that may be received from terminal 1, and a modulator 19 (MOD) to transmit information to terminal 1. The transponder is generally synchronized by means of a clock (CLK) extracted, by a block 20, from the high-frequency signal recovered across capacitor C2 before rectification. Most often, all the electronic circuits of transponder 10 are integrated in a same chip.
To transmit the data from transponder 10 to unit 1, modulator 19 controls a stage of modulation (back modulation) of resonant circuit L2C2. This modulation stage is generally formed of an electronic switch (for example, a transistor T) and of a resistor R, in series between terminals 14 and 15. Transistor T is controlled at a so-called sub-carrier frequency (for example, 847.5 kHz), much smaller (generally with a ratio of at least 10) than the frequency of the excitation signal of the oscillating circuit of terminal 1 (for example, 13.56 MHz). When switch T is closed, the oscillating circuit of the transponder is submitted to an additional damping as compared to the load formed of circuits 16, 17, 18, 19 and 20, so that the transponder draws a greater amount of power from the high frequency field. On the side of terminal 1, amplifier 3 maintains the amplitude of the high-frequency excitation signal constant. Accordingly, the power variation of the transponder translates as an amplitude and phase variation of the current in antenna L1. This variation is detected by demodulator 7 of terminal 1, which is either a phase demodulator or an amplitude demodulator. For example, in the case of a phase demodulation, the demodulator detects, in the half-periods of the sub-carrier where switch T of the transponder is closed, a slight phase shift (a few degrees, or even less than one degree) of the carrier of signal Rx with respect to the reference signal. The output of demodulator 7 (generally the output of a band-pass filter centered on the sub-carrier frequency) then provides an image signal of the control signal of switch T that can be decoded (by decoder 8 or directly by microprocessor 6) to restore the binary data.
It should be noted that the terminal does not transmit data while it receives some from a transponder, the data transmission occurring alternately in one direction, then in the other (half-duplex).
FIG. 2 illustrates a conventional example of data transmission from terminal 1 to a transponder 10. This drawing shows an example of shape of the excitation signal of antenna L1 for a transmission of a code 0101. The modulation currently used is an amplitude modulation with a rate of 106 kbits/s (a bit is transmitted in approximately 9.5 μs) much smaller than the frequency (for example, 13.56 MHz) of the carrier coming from oscillator 5 (period of approximately 74 ns). The amplitude modulation is performed either in all or nothing or with a modulation ratio (defined as being the difference of the peak amplitudes (a, b) between the two states (0 and 1), divided by the sum of these amplitudes) smaller than one due to the need for supply of transponder 10. In the example of FIG. 2, the carrier at 13.56 MHz is modulated in amplitude, with a 106-kbit/s rate, with a modulation rate tm of, for example, 10%.
FIG. 3 illustrates a conventional example of a data transmission from transponder 10 to terminal 1. This drawing illustrates an example of the shape of control signal VT of transistor T, provided by modulator 19, and of the corresponding signal Rx received by terminal 1. On the transponder side, the back modulation is generally of resistive type with a carrier (called a sub-carrier) of, for example, 847.5 kHz (period of approximately 1.18 μs). The back modulation is, for example, based on a BPSK-type (binary phase-shift keying) coding at a rate on the order of 106 kbits/s, much smaller than the sub-carrier frequency. In FIG. 3, signal Rx has been shown as “smoothed”, that is, without showing the high frequency carrier (for example, at 13.56 MHz) ripple. In the example of FIG. 3, it has been assumed that each of the three shown bits is different from the preceding bit. Thus, it is, for example, a transmission of a code 010.
It should be noted that, whatever the type of modulation or back modulation used (for example, in amplitude, phase, frequency) and whatever the type of data coding (NRZ, NRZI, Manchester, ASK, BPSK, etc.), the modulation or back modulation is performed digitally, by jumping between two binary levels.
The oscillating circuits of the terminal and of the transponder are generally tuned on the carrier frequency, that is, their resonance frequency is set on the 13.56-MHz frequency. This tuning aims at maximizing the power diffusion to the transponder, which generally is a card of credit card size integrating the different transponder components.
As illustrated in FIG. 3, signal VT is formed of a pulse train at the sub-carrier frequency (for example, 847.5 kHz), a phase shift occurring upon each state change from a bit to the next bit. As concerns the signal recovered on the reader side, it appears not to have a “digital” form, which can make its decoding difficult. Indeed, the shape of signal Rx has, for each bit transmission time (9.4 μs), a non-linear increase beginning (capacitor charge), to reach a maximum approximately at two thirds of the duration of a bit, then an also non-linear decrease. The enable time, that is, the time taken by signal Rx to reach a level decodable by the demodulator, is linked to the oscillating circuits being tuned. The need for power transfer for the remote supply, associated with the desired system range, requires a high quality factor, and thus that the oscillating circuits be tuned. Now, a high quality factor results in a small passband. This results in a limited data flow for the system. Generally, the quality factors are on the order of 10 for the reader and for the transponder.
The transponder may be formed by various objects (key ring, keys, etc.), but now most often is in the form of a credit card integrating all the circuits and the antenna or inductance L2. For an information exchange with a reader or a terminal, the card is brought closer to antenna L1 of the reader. The distance between the reader and the card varies and, in some applications, a very close or tight coupling transmission is used, the antennas being distant from each other by less than two centimeters. Such a tight coupling transmission may be used, for example, to enable a payment by means of a transponder, and thus guarantee that only the transponder that is closest to the terminal is recognized by said terminal.
A problem that is raised when the oscillating circuits are very close to each other is that, if they are substantially tuned, the power transmitted from the terminal to the transponder is such that the transponder heats up (antenna L2 is generally formed of one or several planar spirals at the card periphery). This thermal effect results in deforming the plastic card.
The present invention also aims at providing a solution that may be implemented on the terminal side and/or on the transponder side.
A feature of the present invention is to detune the oscillating circuits of the terminal and/of the transponder when they are in very close or tight coupling relation.
A frequency detuning of an electromagnetic transponder is known from document WO-A-98/29760. This document provides for the antenna of a transponder to be “detuned in frequency or mismatched in impedance, so that the transponder and its electronic circuit absorb less radio field and power. Thus, another transponder located in the vicinity of the mismatched or detuned transponder can receive enough of the radio field to operate properly. The transmission system can then detect or consult this other transponder as if it were alone in the field” of the transmitter. Still according to this document, the mismatch means are used “when the transponder is in an unselected state to limit the power and/or field absorption by the transponder in the unselected state”.
Conversely to this document, the present invention provides a detuned operation in tight coupling. Thus, a feature of the present invention is to provide, for a tight coupling information transmission, a detuned operation of the oscillating circuits of a read (or read/write) terminal and of an electromagnetic transponder remotely supplied by this terminal.
When at least one of the oscillating circuits is detuned from the remote supply carrier frequency, the power received by the transponder increases as the distance from the terminal decreases, but with a reduced range. In this case, there also is a distance at which the received power is maximum for a given detuning condition. This is an optimal coupling, the critical coupling position being the optimal coupling condition when the two oscillating circuits are tuned on the carrier frequency. It should be noted that the optimal coupling coefficient between the two oscillating circuits depends not only on inductances L1 and L2, on capacitors C1 and C2, and on the frequency (which here is a fixed frequency and corresponds to the carrier frequency), but also on series resistance R1 of the terminal, and on the load of the oscillating circuit of the transponder, that is, on the equivalent resistance of the circuits (microprocessor, etc.) and on the back modulation means (for example, resistor R, FIG. 1), added in parallel on capacitor C2 and on inductance L2. This equivalent resistor will be designated hereafter as R2.
More specifically, the present invention provides a method of data transmission between a terminal for generating an electromagnetic field and a transponder, the terminal and the transponder each including an oscillating circuit forming an antenna, and the transponder including an electronic circuit adapted to absorbing and giving back power provided by the terminal field, the oscillating circuits of the transponder and of the terminal being capable of transmitting radio-electric signals of determined frequency, this method consisting of causing a detuning of at least one of the oscillating circuits with respect to the determined frequency when the transponder and the terminal are very close to each other.
According to an embodiment of the present invention, the oscillating circuits are tuned when the transponder is further away from the terminal than the critical coupling position between the two circuits, at least one of the circuits being detuned when the transponder is between this critical coupling position and the terminal.
According to an embodiment of the present invention, the detuning is caused when the respective antennas of the transponder and of the terminal are at less than two centimeters away from each other.
According to an embodiment of the present invention, both oscillating circuits are detuned.
According to an embodiment of the present invention, the data transmission rate from the transponder to the terminal and/or from the terminal to the transponder is modified according to whether the oscillating circuits are or are not tuned to the determined frequency.
According to an embodiment of the present invention, the determined frequency corresponds to the frequency of a remote supply carrier of the transponder.
The present invention also relates to a system of wireless and contactless data transmission between a terminal of generation of an electromagnetic field and at least one transponder having no independent supply means, the terminal and/or the transponder including means for implementing the method of the present invention.
FIG. 6 shows a first embodiment of an electromagnetic transponder according to the present invention provided with means for detuning the oscillating circuit of the transponder;
FIG. 7 shows a second embodiment of an electromagnetic transponder according to the present invention provided with means for detuning the oscillating circuit of the transponder; and
FIG. 8 partially shows a terminal according to the present invention provided with means for determining the distance of a transponder in its field.
A feature of the present invention is to provide detuning the oscillating circuit of a transponder and/or of a read or read/write terminal when in a situation of tight coupling with a terminal, that is, when their respective antennas are located, for example, at less than 2 centimeters from each other.
The consequence of such a detuning is that the operation becomes close to that of a transformer, that is, the quality factor is less. Now, in the conventional tuned operation, a quality factor as high as possible is desired, to optimize the power transfer associated with the transponder remote supply.
The fact of detuning the transponder and the terminal when the coupling is very close has several advantages.
In a detuned operation, the terminal power, that is, the current in the antenna (L1, FIG. 1), may be decreased while transmitting a sufficient power to the card remote supply. Indeed, since the transponder is very close to the terminal, the problem of remote supply range has disappeared. The required power then essentially depends on the transformation ratio (ratio between the number of spirals) of the oscillating circuit inductances. The current decrease required in the antenna suppresses the thermal effect on the transponder side.
It should be noted that the detuning of the transponder's oscillating circuit is only desirable in very close or tight coupling. Accordingly, the present invention enables easily dissociating two operating modes of the system according to whether the transponder is or not very close to the reader. It should also be noted that the coupling coefficient is decreased by the detuning of the oscillating circuit. This is not disturbing since the two oscillating circuits are then very close to each other in a transformer type operation.
Several solutions may be used to detune the oscillating circuits. Indeed, as indicated hereabove, the optimal coupling coefficient depends on the respective values of elements R1, L1, C1 on the terminal side and R2, L2, C2 on the transponder side. It is thus possible to detune either the transponder's oscillating circuit, or the terminal's oscillating circuit, or both.
According to a preferred embodiment of the present invention, it is provided, for efficiency reasons, to detune both circuits. Indeed, according to the present invention, a significant detuning has to be caused with respect to the remote supply carrier frequency. Thus, controllable means for detuning the oscillating circuits are provided, preferably, on the terminal side and on the transponder side.
FIG. 5 partially shows an embodiment of a read/write terminal 1′ of an electromagnetic transponder, provided with means for detuning the oscillating circuit with respect to the carrier frequency (for example, 13.56 MHz). This embodiment includes varying the value of the capacitance (C1, FIG. 1) of the oscillating circuit.
As previously, terminal 1′ includes an oscillating circuit formed of an inductance or antenna L1, in series with a capacitive element 24 and a resistor R1, between an output terminal 2p of an amplifier or antenna coupler 3 and a terminal 2m at a reference potential (generally the ground). Amplifier 3 receives a high frequency transmission signal Tx coming from a modulator 4 (MOD) that receives a reference frequency (signal OSC), for example, from a quartz oscillator (not shown). Modulator 4 receives, if necessary, a data signal to be transmitted. The other components of terminal 1′ are, unless otherwise indicated, similar to those described in relation with FIG. 1.
As illustrated in FIG. 5, capacitive element 24 provided in series with resistor R1 and inductance L1 is controllable by means of signal CTRL, which is provided by a circuit 21 (COMP), the function of which is to detect the phase shift with respect to reference signal REF and to accordingly modify capacitance C1 of element 24.
Variable capacitance 24 may be formed in several ways. Generally, this capacitance must reach a few hundreds of picofarads and withstand, across its terminals, a voltage of more than 100 volts. A diode in which the capacitance of the reverse-biased junction is used as a variable capacitance that depends on this biasing may for example be used. The diode is then connected, by its anode, on the side of reference terminal 2m and by its cathode, on the side of inductance L1. As an alternative, a diode-mounted MOSFET transistor may be used. Be it a diode or a MOSFET transistor, the control performed by means of signal CTRL includes modifying the voltage across the diode or the transistor to modify its capacitance.
For a detuned operation, the phase reference of comparator 21 may for example be modified to modify the control order of the loop that then regulates on another value, the signals to be compared being then phase-shifted by a value other than 90° in base value. It should be noted that, for the optimal coupling to correspond to the shortest possible distance between the terminal and the transponder, capacitance C1 has to be increased with respect to its tuned value. This amounts to decreasing the resonance frequency of the terminal's oscillating circuit. Instead of modifying the reference phase of comparator 21, the bias voltage of element 24 may be shifted, for example, by means of a switched resistor network, controlled by the terminal microprocessor, to make the biasing resistance of element 24 variable.
To detune the oscillating circuit of the transponder, a first solution includes connecting, in parallel with the transponder antenna, two capacitors, one of which is associated in series with a switch to make it controllable. This solution consists of using, for other purposes, an assembly of the type described in document WO-A-98/29760 that provides a frequency detuning of a transponder by means of a modifiable capacitance in the oscillating circuit.
According to the present invention, for the optimal coupling to correspond to the smallest possible distance between the terminal and the transponder, capacitance C2 has to be increased with respect to its tuned value. This amounts to decreasing the resonance frequency of the oscillating circuit of the transponder.
FIG. 6 shows a first embodiment of a transponder 30 according to the present invention. As previously, this transponder is formed from a parallel oscillating circuit including an inductance L2 and a capacitor C2′ between two terminals 11′, 12′ of the circuit.
In the embodiment illustrated in FIG. 6, the rectification performed to extract a D.C. supply voltage Va smoothed by a capacitor Ca is a single-halfwave rectification by means of a diode D, the anode of which is connected to terminal 11 ′ and the cathode of which is connected to positive terminal 14 of capacitor Ca. Voltage reference 15 corresponds to the negative terminal of capacitor Ca directly connected to terminal 12′. Voltage Va is meant for an electronic block 31 including, for example, circuits 16 to 20 of FIG. 1. A capacitor C3 is connected in series with a switch (for example, a MOS transistor) K1 between terminals 11′ and 12′. Switch K1 is controlled by circuit 31 by being closed for a tuned operation.
FIG. 7 shows a second embodiment of a transponder 30′ according to the present invention. According to this embodiment, terminals 11, 12 of the oscillating circuit are connected to the A.C. input terminals of a bridge 13 formed, for example, of diodes D1 to D4 as in FIG. 1. Two rectified output terminals 14, 15 of bridge 13 provide, via smoothing capacitor Ca, voltage Va of supply of electronic block 31.
According to this embodiment, two capacitors C3 and C4 are respectively connected, each, in series with a switch (for example, a MOS transistor) K1, K2, respectively between terminals 11 and 12 and terminals 15. Thus, a first terminal of capacitor C3 is connected to terminal 11, its second terminal being connected, via transistor K1, to terminal 15. A first terminal of capacitor C4 is connected to terminal 12 while its other terminal is connected, via a transistor K2, to terminal 15. Capacitors C3 and C4 are respectively associated with each sign of high frequency A.C. voltage V2 across antenna L2. Capacitors C3 and C4 are thus of same values. Transistors K1 and K2 are controlled by block 31, preferable from a same signal, to be closed when the circuit has to be tuned on the remote supply carrier frequency.
It should be noted that, due to the doubling of the capacitors, a reference node is available (line 15) for the control of switches K1 and K2. Thus, if switches K1 and K2 are formed of N-channel MOS transistors, it is now possible, by a logic signal coming from block 31, to control these switches in all or nothing, which is not possible with the solution advocated by document WO-A-98/29760.
For example, capacitors C2′, C3 and C4 have, each, a capacitance corresponding to half the capacitance (C2, FIG. 1) necessary to tune the oscillating circuit on the reader carrier frequency.
Transponder 30 (FIG. 6) or 30′ (FIG. 7) also includes a resistive back modulation circuit formed, preferably, of two resistors R3, R4 respectively in series with a switch K3, K4 between terminals 14 and 15. Resistors R3 and R4 have different values, respectively high and low.
Consider being between the critical coupling and the terminal, resistor R3, which is of high value, is used to perform the back modulation and transistor K1 (or transistors K1 and K2) is turned off. The system then has a detuned operation close to a transformer operation.
Consider being far from the critical coupling position while being further away from the terminal than this position, that is, consider a loose coupling. Transistor K1 (or transistors K1 and K2) is then turned on and the resistive back modulation is performed by means of resistor R4 that is of smaller value. This then is a conventional operating mode.
It should be noted that the present invention, by using a resistance of small value when away from the terminal, optimizes the system range. The ratio between the respective values of resistors R3 and R4 is, for example, included between 4 and 10 (R3 included between 0.4 and 5 kiloohms and R4 included between 100 and 500 kiloohms) and, preferably, on the order of 6 (for example, approximately 1500 and 250 ohms).
As an alternative, the capacitor(s) used to detune the circuit is (are) also used as back modulation means. In this case, switched resistors R3, K3, and R4, K4 are eliminated and the values of capacitors C2′, C3 (and C4 for the embodiment of FIG. 7) are chosen so that the importance of the detuning is compatible with the phase shift to be detected by the terminal in case of a capacitive modulation. The capacitive modulation directly influences the phase of the voltage across inductance L1 of the terminal without acting upon its amplitude. This eases the phase detection by the terminal. It should be noted that the type of back modulation does not modify the coding, that is, the control signal of the back modulation switch(es) at the carrier frequency.
In the sizing of the oscillating circuit capacitors, account will be taken of the rectifying means used and of the value of smoothing capacitor Ca. Indeed, the conduction periods of the diodes of a bridge (FIG. 7) are generally shorter as compared to the remote supply carrier period than the conduction periods of a single-halfwave rectifying diode (FIG. 6). Accordingly, the duty cycle of action of the back modulation means is different according to the type of rectification performed. Now, this duty cycle has an influence, in particular, on the value of equivalent resistance R2, and thus on the coupling coefficient.
On the transponder side, one of the embodiments of FIGS. 6 and 7 may be used. According to the present invention, their respective electronic circuit is provided with an input DET receiving the local supply voltage Va. Input DET is associated with a circuit (not shown) for measuring voltage Va and with at least one element for storing this measurement. In a specific example of embodiment, this may be a microprocessor (6, FIG. 1). The storage of the values of the measured voltages is performed either analogically or, preferentially, digitally over several bits, the number of which depends on the desired analysis precision.
According to a preferred embodiment of the present invention, the following measurement cycle is periodically performed when the transponder is in the terminal range and, preferably, as soon as the transponder is activated (supplied) by its entering the field of a reader. Transistor K1 (FIG. 6) or transistors K1 and K2 (FIG. 7) are initially on, the oscillating circuit being tuned. The voltage present on terminal DET is measured. Then, transistor(s) K1, K2 is (are) turned off. The circuit is then detuned, its resonance frequency being shifted to, in the case of FIG. 6, more than twice the tuning frequency if capacitors C2′ and C3 have the same value. The voltage on terminal DET is measured again. As an alternative, the first measurement is performed with a detuned circuit. The two obtained values are compared and the result of this comparison is stored, for example on a single bit.
It should be noted that, in a simplified embodiment, it may be enough to determine, before each beginning of a data transmission from the transponder to the terminal, the position of the transponder with respect to the critical coupling.
As a simplified embodiment, the use of a dedicated distance determination input (DET) may be avoided by using an existing input of the microprocessor (contained in block 31) of the transponder). This conventional input controls the available local supply voltage across capacitor Ca with respect to a predetermined threshold. The microprocessor stores (in the form of a bit) the state of this voltage with respect to the threshold. The bit is conventionally used, for example, for detecting whether the voltage recovered by the oscillating circuit is sufficient for the transponder supply, and thus to activate said transponder when it enters the field of a reader. This function exists, for example, in transponder microprocessors, for example, circuits ST16 and ST19 of STMicroelectronics, and may thus be used with no significant modification of the transponder.
The distance determination with respect to the critical coupling has the advantage that the performed distance determination or area detection (tight coupling or loose coupling) resembles a differential measurement. Indeed, the detection is performed with respect to the critical coupling that depends on the system and on its environment. Only at the critical coupling is the recovered voltage threshold maximum when the circuits are tuned. It is thus not necessary to provide a specific reference or distance threshold. In other words, the threshold distance between the two tuned and detuned operating modes is then self-adaptive.
For a distance determination on the terminal side, a system such as described in WO-A97/34250 may for example be used. However, according to a preferred embodiment of the present invention, the determination performed does not require involving the terminal, that is, it needs no reception of data coming from the transponder.
FIG. 8 partially shows a terminal according to the present invention provided with means for determining the distance of a transponder entering its field. FIG. 8 is based on FIG. 5, of which it only shows capacitive element 24 and current measurement element 2.
According to the embodiment of FIG. 8, the voltage across element 24 is measured by a resistive bridge (resistors R5, R6), the midpoint of which is connected to the anode of a diode D5, the cathode of which is connected to a first input of a comparator (COMP) 40. A capacitor C5 connects the cathode of diode D5 to ground 2m. Capacitor C5 thus has across its terminals a D.C. voltage, as the peak amplitude of the voltage at the midpoint of bridge R5-R6. A second input of comparator 40 receives a reference voltage Vref. As previously indicated, when the transponder enters the terminal field, the load that it forms varies the current in oscillating circuit L1C1. Since the oscillating circuits are, by default, tuned, the closer the transponder comes, the more the voltage across the capacitive element decreases. The voltage across capacitor C1 (element 24) is indeed equal to the product of the voltage amplitude (constant) provided by the A.C. generator (amplifier 3) by the quality factor. Now, when the distance decreases, the quality factor also decreases. The output of comparator 40 thus indicates the transponder position with respect to a distance threshold (transformed in a voltage threshold Vref). The output of comparator 40 is, for example, sent to microprocessor 6, to switch the system operation to the mode corresponding to the tight coupling and control the detuning or not of the oscillating circuits.
It should be noted that the fact of maintaining the tuned phase constant by means of the regulation loop enables making the distance-impedance characteristic monotonic, that is, without any point of inflexion, and thus to obtain a reliable distance determination.
It should also be noted that, once the distance determination has been performed by the transponder or the terminal, that of the elements which has not participated in the determination can receive the information by a data transmission from the other element. Thus, the choice of the detuning mode (transponder, terminal, transponder and terminal) is independent from the distance determination mode.
Of course, the present invention is likely to have various alterations, modifications, and improvements which will readily occur to those skilled in the art. In particular, the sizing of the different resistive and capacitive elements depend on the application and, especially, on the application and, especially, on the frequency of the various carriers and on the system range. Similarly, the practical implementation of the different circuits of a transponder or a terminal according to the present invention is within the abilities of those skilled in the art based on the functional indications given hereabove.
Further, the choice of the distance determination mode depends on the application and on the element of the system that is preferentially desired to be modified. Preferably, the two oscillating circuits will be detuned in a very close coupling to optimize the effects of the detuning. It should be noted that, since the elements communicate with each other, the decision and the detuning may be implemented by a single element that then communicates its state to the other.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS2411555Oct 14, 1942Nov 26, 1946Standard Telephones Cables LtdElectric wave filterUS3618089Jan 29, 1969Nov 2, 1971Moran Instr CorpRange and time measure systemUS4068232Feb 12, 1976Jan 10, 1978Fairchild Industries, Inc.Passive encoding microwave transponderUS4209783Mar 22, 1978Jun 24, 1980Tokyo Shibaura Electric Co., Ltd.Object identification systemUS4278977May 4, 1979Jul 14, 1981Rca CorporationRange determining systemUS4408185Nov 13, 1979Oct 4, 1983Elsmark A/SProcess for transferring information and system for carrying out the processUS4593412May 21, 1984Jun 3, 1986Multi-Elmac CompanyIntegrated oscillator antenna for low power, low harmonic radiationUS4656472Jan 23, 1985Apr 7, 1987Walton Charles AProximity identification system with power aided identifierUS4660192Apr 11, 1985Apr 21, 1987Pomatto Sr Robert PSimultaneous AM and FM transmitter and receiverUS4706050Sep 4, 1985Nov 10, 1987Smiths Industries Public Limited CompanyMicrostrip devicesUS4782308Mar 6, 1987Nov 1, 1988Iskra-Sozd Elektrokovinske Industrije N.Sol.OCircuit arrangement of a reading device for electromagnetic identification cardsUS4802080Mar 18, 1988Jan 31, 1989American Telephone And Telegraph Company, At&T Information SystemsPower transfer circuit including a sympathetic resonatorUS4814595Mar 28, 1988Mar 21, 1989Electo-Galil Ltd.Electronic data communications systemUS4827266Feb 19, 1986May 2, 1989Mitsubishi Denki Kabushiki KaishaAntenna with lumped reactive matching elements between radiator and groundplateUS4928108Mar 7, 1989May 22, 1990Bsh Electronics, Ltd.Electrical signal separating device having isolating and matching circuitry for split passband matchingUS4963887Aug 29, 1989Oct 16, 1990Yamatake-Honeywell Co., Ltd.Full duplex transponder systemUS5013898Nov 3, 1987May 7, 1991Mars IncorporatedData detection, power transfer and power regulation for data storage devicesUS5055853Oct 3, 1988Oct 8, 1991Garnier Robert CMagnetic frill generatorUS5099227Dec 18, 1989Mar 24, 1992Indala CorporationProximity detecting apparatusUS5126749Aug 25, 1989Jun 30, 1992Kaltner George WIndividually fed multiloop antennas for electronic security systemsUS5142292Aug 5, 1991Aug 25, 1992Checkpoint Systems, Inc.Coplanar multiple loop antenna for electronic article surveillance systemsUS5202644Jun 11, 1959Apr 13, 1993Ail Systems, Inc.Receiver apparatusUS5214409 *Dec 3, 1991May 25, 1993Avid CorporationMulti-memory electronic identification tagUS5305008Sep 4, 1992Apr 19, 1994Integrated Silicon Design Pty. Ltd.Transponder systemUS5324315 *Aug 12, 1993Jun 28, 1994Medtronic, Inc.Closed-loop downlink telemetry and method for implantable medical deviceUS5452344Nov 16, 1993Sep 19, 1995Datran Systems CorporationCommunication over power linesUS5493267Feb 26, 1993Feb 20, 1996Aktiebolaget ElectroluxArrangement for the transfer of control commands in an apparatus or a machine operated from the mainsUS5504485Jul 21, 1994Apr 2, 1996Amtech CorporationSystem for preventing reading of undesired RF signalsUS5521602Feb 10, 1994May 28, 1996Racom Systems, Inc.Communications system utilizing FSK/PSK modulation techniquesUS5541604Sep 3, 1993Jul 30, 1996Texas Instruments Deutschland GmbhTransponders, Interrogators, systems and methods for elimination of interrogator synchronization requirementUS5550536Aug 17, 1994Aug 27, 1996Texas Instruments Deutschland GmbhCircuit frequency following technique transponder resonantUS5604411Mar 31, 1995Feb 18, 1997Philips Electronics North America CorporationElectronic ballast having a triac dimming filter with preconditioner offset controlUS5619529Jul 11, 1995Apr 8, 1997Mitsubishi Denki Kabushiki KaishaNon-contact IC card and non-contact IC card reader/writerUS5621411Jun 20, 1996Apr 15, 1997Texas Instruments IncorporatedPositioning with RF-ID transpondersUS5691605Aug 9, 1995Nov 25, 1997Philips Electronics North AmericaElectronic ballast with interface circuitry for multiple dimming inputsUS5698837 *Oct 6, 1995Dec 16, 1997Mitsubishi Denki Kabushiki KaishaMethod and system for identifying and communicating with a plurality of contactless IC cardsUS5698838Oct 4, 1995Dec 16, 1997Mitsubishi Denki Kabushiki KaishaNon-contact IC card including antenna circuit with adjustable resonant frequencyUS5701121Dec 12, 1994Dec 23, 1997Uniscan Ltd.Transducer and interrogator deviceUS5703573Jan 11, 1996Dec 30, 1997Sony Chemicals Corp.Transmitter-receiver for non-contact IC card systemUS5767503Aug 30, 1995Jun 16, 1998GemplusMethod for the manufacture of contact-free cardsUS5801372Aug 1, 1997Sep 1, 1998Mitsubishi Denki Kabushiki KaishaNon-contact IC card with antenna switching circuitUS5831257Aug 1, 1997Nov 3, 1998Mitsubishi Denki Kabushiki KaishaNon-contact IC card including phase-locked loop circuitryUS5850416Sep 16, 1997Dec 15, 1998Lucent Technologies, Inc.Wireless transmitter-receiver information deviceUS5874725Aug 1, 1997Feb 23, 1999Mitsubishi Denki Kabushiki KaishaNon-contact IC card with phase variation detectorUS5883582 *Feb 7, 1997Mar 16, 1999Checkpoint Systems, Inc.Anticollision protocol for reading multiple RFID tagsUS5889273 *Sep 18, 1996Mar 30, 1999Kabushiki Kaisha ToshibaWireless communication data storing medium for receiving a plurality of carriers of proximate frequencies and a transmission/receiving methodUS5905444Nov 12, 1996May 18, 1999Siemens AktiengesellschaftAnti-theft system for a motor vehicleUS5955950Jul 24, 1998Sep 21, 1999Checkpoint Systems, Inc.Low noise signal generator for use with an RFID systemUS6014088Nov 29, 1996Jan 11, 2000Ronald Barend Van SantbrinkMethod and system for contactless exchange of data between a read/write unit and one or more information carriersUS6025780Jul 25, 1997Feb 15, 2000Checkpoint Systems, Inc.RFID tags which are virtually activated and/or deactivated and apparatus and methods of using same in an electronic security systemUS6028503Nov 4, 1997Feb 22, 2000U.S. Philips CorporationContactless data transmission and receiving device with a synchronous demodulatorUS6034640Apr 1, 1998Mar 7, 2000Murata Manufacturing Co., Ltd.Antenna deviceUS6070804 *Feb 25, 1998Jun 6, 2000Mitsubishi Denki Kabushiki KaishaNon-contact IC card with monitor for source powerUS6072383Nov 4, 1998Jun 6, 2000Checkpoint Systems, Inc.RFID tag having parallel resonant circuit for magnetically decoupling tag from its environmentUS6075491May 14, 1998Jun 13, 2000Murata Manufacturing Co., Ltd.Chip antenna and mobile communication apparatus using sameUS6100788Dec 29, 1997Aug 8, 2000Storage Technology CorporationMultifunctional electromagnetic transponder device and method for performing sameUS6137411Feb 11, 1997Oct 24, 2000Rso Corporation N.V.Article surveillance systemUS6154635 *Jun 19, 1996Nov 28, 2000Fujitsu Ten LimitedAntenna driving device for transponderUS6172608 *Jun 18, 1997Jan 9, 2001Integrated Silicon Design Pty. Ltd.Enhanced range transponder systemUS6208235Mar 5, 1998Mar 27, 2001Checkpoint Systems, Inc.Apparatus for magnetically decoupling an RFID tagUS6229443Jun 23, 2000May 8, 2001Single Chip SystemsApparatus and method for detuning of RFID tag to regulate voltageUS6243013Jan 8, 1999Jun 5, 2001Intermec Ip Corp.Cascaded DC voltages of multiple antenna RF tag front-end circuitsUS6265962Jun 29, 2000Jul 24, 2001Micron Technology, Inc.Method for resolving signal collisions between multiple RFID transponders in a fieldUS6272320 *Jan 12, 1998Aug 7, 2001Em Microelectronic-Marin SaBase station for a contactless interrogation system comprising a phase locked and voltage controlled oscillatorUS6272321 *Sep 13, 1997Aug 7, 2001Temic Semiconductor GmbhMethod for tuning an oscillating receiver circuit of a transponder built into a RFID systemUS6281794May 25, 1999Aug 28, 2001Intermec Ip Corp.Radio frequency transponder with improved read distanceUS6307468 *Jul 20, 1999Oct 23, 2001Avid Identification Systems, Inc.Impedance matching network and multidimensional electromagnetic field coil for a transponder interrogatorUS6307517Jun 13, 2000Oct 23, 2001Applied Wireless Identifications Group, Inc.Metal compensated radio frequency identification readerUS6393045 *Sep 24, 1998May 21, 2002Wherenet Corp.Spread spectrum baseband modulation of magnetic fields for communications and proximity sensingUS6424820Apr 2, 1999Jul 23, 2002Interval Research CorporationInductively coupled wireless system and methodUS6441804Feb 1, 1999Aug 27, 2002Kye Systems Corp.Transmitter and receiver for use in a wireless cursor control systemUS6446049Sep 29, 1998Sep 3, 2002Pole/Zero CorporationMethod and apparatus for transmitting a digital information signal and vending system incorporating sameUS6491230Jul 20, 1999Dec 10, 2002Thomson-Csf DetexisContactless badge readerDE2835549A1Aug 14, 1978Mar 1, 1979Joergen Born RasmussenRemote control circuit for coded receivers - operates with direct modification of power supply waveform by positive and negative half-wave clippingDE4444984A Title not availableDE19546928A1Dec 15, 1995Jun 19, 1997Diehl Ident GmbhInductive high frequency information signal transmitterDE19621076A1May 24, 1996Nov 27, 1997Siemens AgVorrichtung und Verfahren zum kontaktlosen Übertragen von Energie oder DatenDE19632282A1Aug 9, 1996Feb 19, 1998Holzer Walter Prof Dr H C IngVerfahren und Einrichtung zur Helligkeitssteuerung von LeuchtstofflampenEP0038877A1Apr 28, 1980Nov 4, 1981Paul RouetProcess and system for transmitting information and instructions on an alternating current distribution networkEP0369622A2Oct 24, 1989May 23, 1990Security Tag Systems, Inc.Proximity reading of coded tagEP0568067A1Apr 29, 1993Nov 3, 1993Texas Instruments IncorporatedRFID system with controlled chargeEP0579332A1Jul 14, 1993Jan 19, 1994N.V. Nederlandsche Apparatenfabriek NEDAPElectromagnetic detection systemEP0645840A1Sep 23, 1994Mar 29, 1995N.V. Nederlandsche Apparatenfabriek NEDAPAntenna configuration of an electromagnetic detection system and an electromagnetic detection system comprising such antenna configurationEP0768540A1Oct 9, 1996Apr 16, 1997Texas Instruments Deutschland GmbhTransponder system and methodEP0857981A1Feb 5, 1997Aug 12, 1998EM Microelectronic-Marin SABase station of a remote interrogation system with a voltage and phase controlled oscillatorEP0902475A2Sep 15, 1998Mar 17, 1999Microchip Technology Inc.A single-sided package including an integrated circuit semiconductor chip and inductive coil and method thereforFR2114026A1 Title not availableFR2746200A1 Title not availableFR2757952A1 Title not availableGB2298553A Title not availableGB2321726A Title not availableJPH07245946A Title not availableJPH10145267A Title not availableJPH10203066A Title not availableWO1993017482A2Feb 26, 1993Sep 2, 1993Scantronic LimitedPower supply and smoke sensor for alarm systemWO1998020363A1Sep 26, 1997May 14, 1998Philips Electronics N.V.Contactless data transmission and receiving device with a synchronous demodulatorWO1999033017A1Dec 21, 1998Jul 1, 1999Advanced Technology Communications LimitedTag and detection systemWO1999043096A1Dec 18, 1998Aug 26, 1999Motorola Inc.Data communications terminal and method of adjusting a power signal generated therefrom* Cited by examinerNon-Patent CitationsReference1French Search Report from French Patent Application No. 00 06061, filed May 12, 2000.2French Search Report from French Patent Application No. 00 06064, filed May 12, 2000.3French Search Report from French Patent Application No. 00 06065, filed May 12, 2000.4French Search Report from French Patent Application No. 00 06071, filed May 12, 2000.5French Search Report from French Patent Application No. 00 06302, filed May 17, 2000.6French Search Report from French Patent Application No. 00/01214, filed Jan. 31, 2000.7French Search Report from French Patent Application No. 00/06301, filed May 17, 2000.8French Search Report from French Patent Application No. 98 08024, filed Jun. 22, 1998.9French Search Report from French Patent Application No. 98 08025, filed Jun. 22, 1998.10French Search Report from French Patent Application No. 99 04544, filed Apr. 7, 1999.11French Search Report from French Patent Application No. 99 04545, filed Apr. 7, 1999.12French Search Report from French Patent Application No. 99 04546 , filed Apr. 7, 1999.13French Search Report from French Patent Application No. 99 04547, filed Apr. 7, 1999.14French Search Report from French Patent Application No. 99 04548, filed Apr. 7, 1999.15French Search Report from French Patent Application No. 99 04549, filed Apr. 7, 1999.16French Search Report from French Patent Application No. 99 07024, filed May 31 1999.17French Search Report from French Patent Application No. 99 09563, filed Jul. 20, 1999.18French Search Report from French Patent Application No. 99 09564, filed Jul. 20, 1999.Referenced byCiting PatentFiling datePublication dateApplicantTitleUS6792288 *Jul 7, 1999Sep 14, 2004Commissariat A L'energie AtomiqueAnalog interface for autonomous data exchange circuitUS6879246May 11, 2001Apr 12, 2005Stmicroelectronics S.A.Evaluation of the number of electromagnetic transponders in the field of a readerUS6940467Jan 7, 2004Sep 6, 2005Atmel Germany GmbhCircuit arrangement and method for deriving electrical power from an electromagnetic fieldUS6960985Jan 26, 2001Nov 1, 2005Stmicroelectronics S.A.Adaptation of the transmission power of an electromagnetic transponder readerUS7005967May 11, 2001Feb 28, 2006Stmicroelectronics S.A.Validation of the presence of an electromagnetic transponder in the field of an amplitude demodulation readerUS7023391May 17, 2001Apr 4, 2006Stmicroelectronics S.A.Electromagnetic field generation antenna for a transponderUS7046121Aug 9, 2001May 16, 2006Stmicroelectronics S.A.Detection of an electric signature of an electromagnetic transponderUS7046146May 17, 2001May 16, 2006Stmicroelectronics S.A.Electromagnetic field generation device for a transponderUS7049935Jul 13, 2000May 23, 2006Stmicroelectronics S.A.Sizing of an electromagnetic transponder system for a dedicated distant coupling operationUS7049936May 11, 2001May 23, 2006Stmicroelectronics S.A.Validation of the presence of an electromagnetic transponder in the field of a readerUS7058357Jul 13, 2000Jun 6, 2006Stmicroelectronics S.A.Sizing of an electromagnetic transponder system for an operation in extreme proximityUS7107008 *May 11, 2001Sep 12, 2006Stmicroelectronics S.A.Validation of the presence of an electromagnetic transponder in the field of a phase demodulation readerUS7151436Jan 7, 2004Dec 19, 2006Atmel Germany GmbhReceiving/backscattering arrangement and method with two modulation modes for wireless data transmission as well as modulation arrangement thereforUS7263330Oct 27, 2005Aug 28, 2007Stmicroelectronics S.A.Validation of the presence of an electromagnetic transponder in the field of a phase demodulation readerUS7519400May 27, 2005Apr 14, 2009Dei Headquarters, Inc.Multi-modulation remote control communication systemUS7535362 *Feb 9, 2006May 19, 2009Atmel Germany GmbhCircuit arrangement and method for supplying power to a transponderUS7603082 *Jun 23, 2005Oct 13, 2009Stmicroelectronics S.A.Impedance matching of an electromagnetic transponder readerUS7689195 *Jun 16, 2005Mar 30, 2010Broadcom CorporationMulti-protocol radio frequency identification transponder tranceiverUS7796710 *Nov 8, 2005Sep 14, 2010Kabushiki Kaisha ToshibaDigital signal demodulator and wireless receiver using the sameUS7868481 *Nov 19, 2007Jan 11, 2011Infineon Technologies AgEmergency capacitor for a contactless deviceUS8130080Sep 14, 2006Mar 6, 2012Giesecke & Devrient GmbhTransponder actuatable switching deviceUS8130159Sep 15, 2009Mar 6, 2012Stmicroelectronics S.A.Electromagnetic field generation antenna for a transponderUS8274370Jan 12, 2007Sep 25, 2012Atmel CorporationModulator and modulation method for a wireless data transmission deviceUS8482388 *Jun 15, 2010Jul 9, 2013Stmicroelectronics (Rousset) SasAuthentication of a terminal by an electromagnetic transponderUS8552741 *Apr 28, 2009Oct 8, 2013Stmicroelectronics (Rousset) SasDetection of a distance variation with respect to a rotation axisUS8669676Dec 30, 2009Mar 11, 2014Witricity CorporationWireless energy transfer across variable distances using field shaping with magnetic materials to improve the coupling factorUS8692412Mar 30, 2010Apr 8, 2014Witricity CorporationTemperature compensation in a wireless transfer systemUS8723366Mar 10, 2010May 13, 2014Witricity CorporationWireless energy transfer resonator enclosuresUS8729737Feb 8, 2012May 20, 2014Witricity CorporationWireless energy transfer using repeater resonatorsUS8760007Dec 16, 2009Jun 24, 2014Massachusetts Institute Of TechnologyWireless energy transfer with high-Q to more than one deviceUS8760008Dec 30, 2009Jun 24, 2014Massachusetts Institute Of TechnologyWireless energy transfer over variable distances between resonators of substantially similar resonant frequenciesUS8766485Dec 30, 2009Jul 1, 2014Massachusetts Institute Of TechnologyWireless energy transfer over distances to a moving deviceUS8772971Dec 30, 2009Jul 8, 2014Massachusetts Institute Of TechnologyWireless energy transfer across variable distances with high-Q capacitively-loaded conducting-wire loopsUS8772972Dec 30, 2009Jul 8, 2014Massachusetts Institute Of TechnologyWireless energy transfer across a distance to a moving deviceUS8772973Aug 20, 2010Jul 8, 2014Witricity CorporationIntegrated resonator-shield structuresUS8791599Dec 30, 2009Jul 29, 2014Massachusetts Institute Of TechnologyWireless energy transfer to a moving device between high-Q resonatorsUS8847548Aug 7, 2013Sep 30, 2014Witricity CorporationWireless energy transfer for implantable devicesUS8875086Dec 31, 2013Oct 28, 2014Witricity CorporationWireless energy transfer modeling toolUS8901778Oct 21, 2011Dec 2, 2014Witricity CorporationWireless energy transfer with variable size resonators for implanted medical devicesUS8901779Oct 21, 2011Dec 2, 2014Witricity CorporationWireless energy transfer with resonator arrays for medical applicationsUS8907531Oct 21, 2011Dec 9, 2014Witricity CorporationWireless energy transfer with variable size resonators for medical applicationsUS8907761 *Jun 15, 2010Dec 9, 2014Stmicroelectronics (Rousset) SasAuthentication of an electromagnetic terminal-transponder couple by the terminalUS8912687Nov 3, 2011Dec 16, 2014Witricity CorporationSecure wireless energy transfer for vehicle applicationsUS8922066Oct 17, 2011Dec 30, 2014Witricity CorporationWireless energy transfer with multi resonator arrays for vehicle applicationsUS8922338 *Jun 15, 2010Dec 30, 2014Stmicroelectronics (Rousset) SasPower management in an electromagnetic transponderUS8922341May 22, 2013Dec 30, 2014Stmicroelectronics (Rousset) SasAuthentication of a terminal by an electromagnetic transponderUS8928276Mar 23, 2012Jan 6, 2015Witricity CorporationIntegrated repeaters for cell phone applicationsUS8933594Oct 18, 2011Jan 13, 2015Witricity CorporationWireless energy transfer for vehiclesUS8937408Apr 20, 2011Jan 20, 2015Witricity CorporationWireless energy transfer for medical applicationsUS8946938Oct 18, 2011Feb 3, 2015Witricity CorporationSafety systems for wireless energy transfer in vehicle applicationsUS8947186Feb 7, 2011Feb 3, 2015Witricity CorporationWireless energy transfer resonator thermal managementUS8957549Nov 3, 2011Feb 17, 2015Witricity CorporationTunable wireless energy transfer for in-vehicle applicationsUS8963488Oct 6, 2011Feb 24, 2015Witricity CorporationPosition insensitive wireless chargingUS8988196 *Jun 3, 2010Mar 24, 2015Stmicroelectronics (Rousset) SasPower recovery by an electromagnetic transponderUS9035499Oct 19, 2011May 19, 2015Witricity CorporationWireless energy transfer for photovoltaic panelsUS9065286Jun 12, 2014Jun 23, 2015Massachusetts Institute Of TechnologyWireless non-radiative energy transferUS9065423Sep 14, 2011Jun 23, 2015Witricity CorporationWireless energy distribution systemUS9093853Jan 30, 2012Jul 28, 2015Witricity CorporationFlexible resonator attachmentUS9095729Jan 20, 2012Aug 4, 2015Witricity CorporationWireless power harvesting and transmission with heterogeneous signalsUS9101777Aug 29, 2011Aug 11, 2015Witricity CorporationWireless power harvesting and transmission with heterogeneous signalsUS9105959Sep 4, 2012Aug 11, 2015Witricity CorporationResonator enclosureUS9106203Nov 7, 2011Aug 11, 2015Witricity CorporationSecure wireless energy transfer in medical applicationsUS9160203Oct 6, 2011Oct 13, 2015Witricity CorporationWireless powered televisionUS9184595Feb 13, 2010Nov 10, 2015Witricity CorporationWireless energy transfer in lossy environmentsUS9246336Jun 22, 2012Jan 26, 2016Witricity CorporationResonator optimizations for wireless energy transferUS9287607Jul 31, 2012Mar 15, 2016Witricity CorporationResonator fine tuningUS9291703 *Mar 28, 2012Mar 22, 2016OrangeMethod and a device for identifying the position of a transponderUS9306635Jan 28, 2013Apr 5, 2016Witricity CorporationWireless energy transfer with reduced fieldsUS9318257Oct 18, 2012Apr 19, 2016Witricity CorporationWireless energy transfer for packagingUS9318898Jun 25, 2015Apr 19, 2016Witricity CorporationWireless power harvesting and transmission with heterogeneous signalsUS9318922Mar 15, 2013Apr 19, 2016Witricity CorporationMechanically removable wireless power vehicle seat assemblyUS9343922Jun 27, 2012May 17, 2016Witricity CorporationWireless energy transfer for rechargeable batteriesUS9344156Apr 18, 2012May 17, 2016Stmicroelectronics (Rousset) SasProtection of communication by an electromagnetic transponderUS9356656Apr 18, 2012May 31, 2016Stmicroelectronics (Rousset) SasAssistance for positioning a transponderUS9369182Jun 21, 2013Jun 14, 2016Witricity CorporationWireless energy transfer using variable size resonators and system monitoringUS9384885Aug 6, 2012Jul 5, 2016Witricity CorporationTunable wireless power architecturesUS9396867Apr 14, 2014Jul 19, 2016Witricity CorporationIntegrated resonator-shield structuresUS9404954Oct 21, 2013Aug 2, 2016Witricity CorporationForeign object detection in wireless energy transfer systemsUS9407307Apr 18, 2012Aug 2, 2016Stmicroelectronics (Rousset) SasTransponder positioning aidUS9421388Aug 7, 2014Aug 23, 2016Witricity CorporationPower generation for implantable devicesUS9442172Sep 10, 2012Sep 13, 2016Witricity CorporationForeign object detection in wireless energy transfer systemsUS9444265May 22, 2012Sep 13, 2016Massachusetts Institute Of TechnologyWireless energy transferUS9444520Jul 19, 2013Sep 13, 2016Witricity CorporationWireless energy transfer convertersUS9449757Nov 18, 2013Sep 20, 2016Witricity CorporationSystems and methods for wireless power system with improved performance and/or ease of useUS9450421Feb 24, 2015Sep 20, 2016Massachusetts Institute Of TechnologyWireless non-radiative energy transferUS9450422Mar 24, 2015Sep 20, 2016Massachusetts Institute Of TechnologyWireless energy transferUS9465064Oct 21, 2013Oct 11, 2016Witricity CorporationForeign object detection in wireless energy transfer systemsUS9496719Sep 25, 2014Nov 15, 2016Witricity CorporationWireless energy transfer for implantable devicesUS9507975Apr 18, 2012Nov 29, 2016Stmicroelectronics (Rousset) SasProtection of communication between an electromagnetic transponder and a terminalUS9508033Jun 3, 2010Nov 29, 2016Stmicroelectronics (Rousset) SasPower management in an electromagnetic transponderUS9509147Mar 8, 2013Nov 29, 2016Massachusetts Institute Of TechnologyWireless energy transferUS9515494Apr 9, 2015Dec 6, 2016Witricity CorporationWireless power system including impedance matching networkUS9515495Oct 30, 2015Dec 6, 2016Witricity CorporationWireless energy transfer in lossy environmentsUS9544683Oct 17, 2013Jan 10, 2017Witricity CorporationWirelessly powered audio devicesUS9577436Jun 6, 2011Feb 21, 2017Witricity CorporationWireless energy transfer for implantable devicesUS9584189Jun 21, 2013Feb 28, 2017Witricity CorporationWireless energy transfer using variable size resonators and system monitoringUS9595378Sep 19, 2013Mar 14, 2017Witricity CorporationResonator enclosureUS9596005Jun 21, 2013Mar 14, 2017Witricity CorporationWireless energy transfer using variable size resonators and systems monitoringUS20010015697 *Jan 26, 2001Aug 23, 2001Luc WuidartAdaptation of the transmission power of an electromagnetic transponder readerUS20020003498 *May 17, 2001Jan 10, 2002Luc WuidartElectromagnetic field generation antenna for a transponderUS20020008611 *May 11, 2001Jan 24, 2002Luc WuidartValidation of the presence of an electromagnetic transponder in the field of an amplitude demodulation readerUS20020008612 *May 11, 2001Jan 24, 2002Luc WuidartValidation of the presence of an electromagnetic transponder in the field of a phase demodulation readerUS20020011922 *May 11, 2001Jan 31, 2002Luc WuidartValidation of the presence of an electromagnetic transponder in the field of a readerUS20020017991 *May 17, 2001Feb 14, 2002Luc WuidartElectromagnetic field generation device for a transponderUS20020021207 *May 11, 2001Feb 21, 2002Luc WuidartEvaluation of the number of electromagnetic transponders in the field of a readerUS20030164742 *Aug 9, 2001Sep 4, 2003Luc WuidartDetection of an electric signature of an electromagnetic transponderUS20030169169 *Aug 16, 2001Sep 11, 2003Luc WuidartAntenna generating an electromagnetic field for transponderUS20040145452 *Jan 7, 2004Jul 29, 2004Atmel Germany GmbhReceiving/backscattering arrangement and method with two modulation modes for wireless data transmission as well as modulation arrangement thereforUS20050285718 *Jun 23, 2005Dec 29, 2005Stmicroelectronics, S.A.Impedance matching of an electromagnetic transponder readerUS20060103561 *Nov 8, 2005May 18, 2006Kazuhide AbeDigital signal demodulator and wireless receiver using the sameUS20060111043 *Oct 27, 2005May 25, 2006Stmicroelectronics S.A.Validation of the presence of an electromagnetic transponder in the field of a phase demodulation readerUS20060172702 *Mar 28, 2006Aug 3, 2006St MicroelectronicsSizing of an electromagnetic transponder system for an operation in extreme proximityUS20060187049 *Feb 9, 2006Aug 24, 2006Atmel Germany GmbhCircuit arrangement and method for supplying power to a transponderUS20060238301 *Jun 16, 2005Oct 26, 2006Jiangfeng WuMulti-protocol radio frequency identification transponder tranceiverUS20070008087 *May 27, 2005Jan 11, 2007Normand DeryMulti-modulation remote control communication systemUS20070109102 *Jan 12, 2007May 17, 2007Atmel Germany GmbhModulator and modulation method for a wireless data transmission deviceUS20090096587 *Sep 14, 2006Apr 16, 2009Klaus FinkenzellerTransponder Actuatable Switching DeviceUS20090127934 *Nov 19, 2007May 21, 2009Infineon Technologies AgEmergency capacitor for a contactless deviceUS20100039337 *Sep 15, 2009Feb 18, 2010Stmicroelectronics S.A.Electromagnetic field generation antenna for a transponderUS20100102640 *Dec 30, 2009Apr 29, 2010Joannopoulos John DWireless energy transfer to a moving device between high-q resonatorsUS20100127575 *Dec 16, 2009May 27, 2010Joannopoulos John DWireless energy transfer with high-q to more than one deviceUS20100133918 *Dec 30, 2009Jun 3, 2010Joannopoulos John DWireless energy transfer over variable distances between resonators of substantially similar resonant frequenciesUS20100133919 *Dec 30, 2009Jun 3, 2010Joannopoulos John DWireless energy transfer across variable distances with high-q capacitively-loaded conducting-wire loopsUS20100181845 *Mar 30, 2010Jul 22, 2010Ron FiorelloTemperature compensation in a wireless transfer systemUS20100187911 *Dec 30, 2009Jul 29, 2010Joannopoulos John DWireless energy transfer over distances to a moving deviceUS20100231340 *Mar 10, 2010Sep 16, 2010Ron FiorelloWireless energy transfer resonator enclosuresUS20100259110 *Apr 9, 2010Oct 14, 2010Kurs Andre BResonator optimizations for wireless energy transferUS20100277121 *Apr 29, 2010Nov 4, 2010Hall Katherine LWireless energy transfer between a source and a vehicleUS20100328027 *Jun 15, 2010Dec 30, 2010Stmicroelectronics (Rousset) SasAuthentication of an electromagnetic terminal-transponder couple by the terminalUS20100328046 *Jun 15, 2010Dec 30, 2010Stmicroelectronics (Rousset) SasAuthentication of a terminal by an electromagnetic transponderUS20110018692 *May 28, 2010Jan 27, 2011Patrick SmithMethods and Systems for Validating Code from a Wireless DeviceUS20110043049 *Dec 29, 2009Feb 24, 2011Aristeidis KaralisWireless energy transfer with high-q resonators using field shaping to improve kUS20110074346 *Oct 6, 2010Mar 31, 2011Hall Katherine LVehicle charger safety system and methodUS20110095618 *Apr 13, 2010Apr 28, 2011Schatz David AWireless energy transfer using repeater resonatorsUS20110095769 *Apr 28, 2009Apr 28, 2011St Microelectronic S.A.Detection of a distance variation with respect to a rotation axisUS20110121920 *Feb 7, 2011May 26, 2011Kurs Andre BWireless energy transfer resonator thermal managementUS20110140852 *Jun 15, 2010Jun 16, 2011Stmicroelectronics (Rousset) SasPower management in an electromagnetic transponderUS20120105012 *Jun 3, 2010May 3, 2012Stmicroelectronics (Rousset) SasPower recovery by an electromagnetic transponderUS20140024391 *Mar 28, 2012Jan 23, 2014OrangeMethod and a device for identifying the position of a transponderWO2007031318A1 *Sep 14, 2006Mar 22, 2007Giesecke & Devrient GmbhTransponder actuatable switching device* Cited by examinerClassifications U.S. Classification340/10.4, 345/41, 340/10.2International ClassificationG06K7/00, H04B1/59, G01S13/74, G06K19/07, H04B5/02Cooperative ClassificationG06K19/0723, G06K19/0701, G06K7/0008European ClassificationG06K19/07A, G06K7/00E, G06K19/07TLegal EventsDateCodeEventDescriptionJun 27, 2000ASAssignmentOwner name: STMICROELECTRONICS S.A., FRANCEFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WUIDART, LUC;BARDOUILLET, MICHEL;ENGUENT, JEAN-PIERRE;REEL/FRAME:010885/0390;SIGNING DATES FROM 20000427 TO 20000428Aug 29, 2007FPAYFee paymentYear of fee payment: 4Aug 29, 2011FPAYFee paymentYear of fee payment: 8Aug 27, 2015FPAYFee paymentYear of fee payment: 12RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services