Source: http://www.google.com/patents/US6784785?dq=5579430
Timestamp: 2014-03-16 04:49:48
Document Index: 488246612

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

Patent US6784785 - Duplex transmission in an electromagnetic transponder system - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA method of transmission between two elements chosen from a terminal and a transponder, each element including an oscillating circuit, a modulator and a demodulator, including simultaneously performing a transmission in amplitude modulation of a signal transmitted from a first to a second element and...http://www.google.com/patents/US6784785?utm_source=gb-gplus-sharePatent US6784785 - Duplex transmission in an electromagnetic transponder systemAdvanced Patent SearchPublication numberUS6784785 B1Publication typeGrantApplication numberUS 09/543,824Publication dateAug 31, 2004Filing dateApr 5, 2000Priority dateApr 7, 1999Fee statusPaidAlso published asDE60041298D1, EP1043678A1, EP1043678B1Publication number09543824, 543824, US 6784785 B1, US 6784785B1, US-B1-6784785, US6784785 B1, US6784785B1InventorsLuc Wuidart, Michel Bardouillet, Jean-Pierre EnguentOriginal AssigneeStmicroelectronics S.A.Export CitationBiBTeX, EndNote, RefManPatent Citations (98), Non-Patent Citations (11), Referenced by (9), Classifications (14), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetDuplex transmission in an electromagnetic transponder systemUS 6784785 B1Abstract A method of transmission between two elements chosen from a terminal and a transponder, each element including an oscillating circuit, a modulator and a demodulator, including simultaneously performing a transmission in amplitude modulation of a signal transmitted from a first to a second element and a transmission of a signal from the second to the first element adapted to being submitted to a phase demodulation in the latter, and wherein the amplitude modulation rate is smaller than 100%.
What is claimed is: 1. A method of transmission between a terminal and a transponder, each including an oscillating circuit, a modulation means and a demodulation means, the method including steps of simultaneously performing an amplitude-modulated transmission of a signal transmitted from the terminal to the transponder and a transmission of a signal from the transponder to the terminal adapted to being submitted to a phase demodulation in the terminal, and wherein an amplitude modulation ratio is smaller than 100%, the method further comprising regulating a signal phase in the oscillating circuit of the terminal with respect to a reference value, a response time of phase regulation being shorter than an amplitude modulation period and longer than a period of a signal that will have to undergo a phase demodulation.
means for comparing transmitted and received signals clipped by respective clipping means; and means for regulating a signal phase in the oscillating circuit of the terminal with respect to a reference value, a response time of phase regulation being shorter than an amplitude modulation period and longer than a period of a signal that will have to undergo a phase demodulation. 6. A transponder for implementing a method of transmission between a terminal and the transponder, each including an oscillating circuit, a modulation means and a demodulation means, the method including steps of simultaneously performing an amplitude-modulated transmission of a signal transmitted from the terminal to the transponder and a transmission of a signal from the transponder to the terminal adapted to being submitted to a phase demodulation in the terminal, and wherein an amplitude modulation ratio is smaller than 100%, the transponder including an amplitude demodulation means sized according to attenuation introduced by a back modulation means.
Indeed, the previously-described conventional transmission method does not enable simultaneous transmission from the transponder to the terminal and from the terminal to the transponder. Among the problems raised by such a bidirectional method, there is, in particular, the risk for the transmission from one of the system elements�terminal or transponder�to the other�transponder or terminal�to disturb the decoding of the data received from the other element.
SUMMARY OF THE INVENTION The present invention aims at providing a novel transmission method that is bidirectional (duplex method).
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a conventional electromagnetic transponder associated with a conventional terminal;
DETAILED DESCRIPTION The same elements have been referred to with the same references in the different drawings, and the drawings have been drawn out of scale. For clarity, only those elements necessary to the understanding of the present invention have been shown in the drawings and will be described hereafter. In particular, the structure of a transponder and the structure of the digital data processing elements, on the read terminal side, have not been detailed. Further, the timing diagrams of FIGS. 2A to 4E are not drawn to scale.
The method of the present invention applies to transponder systems. More specifically, the present invention applies to such systems in which the transmissions from a first element�terminal or transponder�to a second element�transponder or terminal�are performed according to a first type of�phase or amplitude�modulation and in which the demodulations of the transmissions from the second element to the first one are performed according to a second type of modulation distinct from the first one. Further, the amplitude modulation will be a modulation of a ratio smaller than 100%.
Thus, the transponder draws, as previously discussed, from the carrier modulated by the terminal, the power necessary to its operation, especially, on the one hand, the power necessary for the control of switch T by microprocessor μP 17 and, on the other hand, by performing a simultaneous transmission, the power dissipated during the closed periods of switch T by the addition of resistor R in the circuit. Such a drawing can result in wrong readings by the transponder, especially during closed periods of switch T. Indeed, the corresponding load increase of the oscillating circuit (L2C2) of the transponder with respect to the oscillating circuit (L1C1) of the terminal causes an attenuation of the received signal that alters the demodulation. Indeed, assuming that from an initial time t0, the transponder starts receiving sequence 1011 of the example of FIG. 2A, and assuming that during the transmission of the first bit (1), the transponder causes the turning-on of switch T, an attenuation of the first received bit (1) can be observed. Such an attenuation risks altering the discrimination between the level of such a signal corresponding to an attenuated datum �1� and the subsequent signal voluntarily attenuated in amplitude at the terminal level to transmit datum �0�.
More specifically, demodulator 7 performs the demodulation by generating a pulse-width modulation signal (PWM) of a frequency that is double the reference signal and the duty ratio of which depends on the phase shift. It should be noted that the reference signal and the received signal (to be demodulated) are significantly attenuated at the input of the demodulator to be compatible with low voltage logic circuits. It should also be noted that the demodulator does not aim at measuring the phase shift�its absolute value�but only at detecting the existence of a phase variation to restore a signal at the sub-carrier frequency that is then decoded. Demodulator 7 is for example an X-OR logic gate.
FIGS. 4A to 4E illustrate an embodiment of a demodulation of data received from the transponder by the terminal, for example, by means of an X-OR gate. The shapes of the different signals are shown in the absence�to the left of the drawings�and in the presence�to the right of the drawings�of additional resistive load R in the transponder circuit. In other words, the left-hand portions of FIGS. 4A to 4E correspond to open periods of switch T and their right-hand portions correspond to closed periods of switch T.
FIG. 4B illustrates a first example of a signal Rx1 received from the transponder by the terminal. Signal Rx1 is a signal back modulated by the transponder from the carrier, not attenuated in amplitude. At the input of the X-OR gate, as illustrated in FIG. 4B, signal Rx1 is phase-shifted by 90� with respect to reference signal Ref by the sizing of the circuit components, to obtain a duty ratio (ratio of the high state period to the signal period) of fifty percent when switch T is open.
When switch T is closed, as will be better understood by comparing the left-hand and right-hand portions of FIG. 4B, a phase shift Δφ corresponding to the phase modulation introduced in the sub-carrier by the back modulation means adds to the basic 90� phase shift of signal Rx1 with respect to signal Ref. Phase shift Δφ lasts for at least one half sub-carrier period. It should be noted that during closed periods of switch T, signal Rx1 is further attenuated by the additional resistive load introduced.
When switch T is open, to the left of the drawing, signal Vφ1 is a pulse-width modulation signal of a 50% duty ratio. As clearly appears from the comparison of FIGS. 4A to 4C, the rising edges of signal Vφ1 are controlled by the zero crossing of signal Ref and the falling edges are controlled by the zero crossing of signal Rx1. Two rising edges are thus separated by a time interval t1 corresponding to one half-period (approximately 37 ns) of the carrier provided by oscillator 5. Time interval t2 separating a rising edge from a falling edge then corresponds to the phase shift between two zero crossings of signals Ref and Rx1, that is, 90�, that is, one quarter of a period (approximately 13.5 ns).
FIG. 4D illustrates a second example of a signal Rx2 received by the terminal. Signal Rx2 is a signal back modulated from an attenuated carrier. It should indeed be reminded that the terminal, to transmit data to the transponder, performs an amplitude modulation with a modulation ratio under 100%. Then, as illustrated in FIG. 4D, even when transistor T is off, to the left of the drawings, signal Rx2 has deformed curves with respect to the reference signal (FIG. 4A). This effect is further enhanced, as illustrated in the right-hand portion of FIG. 4D when switch T is closed under the additional attenuation effect resulting from the resistive load. As previously, when switch T is open, signal Rx2 is phase-shifted by 90� only with respect to the reference signal and when switch T is closed, an additional phase shift, which is an image of the back modulation, appears.
When switch T is closed�to the right of the drawing�the duty ratio of output signal Vφ2 is further modified due to the phase shift and to the additional attenuation introduced by the resistive load.
Another advantage of the present invention is that each of the elements�terminal or transponder�remains useable, if necessary, to implement a half-duplex method.
Advantage may be taken from the phase regulation loop to further improve or optimize the demodulation. For this purpose, the response time of the phase regulation loop is chosen to be fast as compared to the data transmission rate by amplitude modulation (106 kbits/s) and slow as compared to the sub-carrier period (847.5 kHz), and thus also as compared to the carrier period (13.56 MHz). Thus, the phase variations of the carrier and the phase shifts of the sub-carrier due to the back modulation are too fast to be taken into account by the regulation loop and can thus be decoded. However, parasitic phase variations due to the amplitude modulation that occur at the rate of the amplitude changes are taken into account and the regulation loop then restores the (static) phase shift between signal Rx and the reference signal at the base value (90�).
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No. 98 08025, filed Jun. 22, 1998.Referenced byCiting PatentFiling datePublication dateApplicantTitleUS7263330Oct 27, 2005Aug 28, 2007Stmicroelectronics S.A.Validation of the presence of an electromagnetic transponder in the field of a phase demodulation readerUS7573368 *Dec 20, 2005Aug 11, 2009Stmicroelectronics SaElectromagnetic transponder with no autonomous power supplyUS7689195 *Jun 16, 2005Mar 30, 2010Broadcom CorporationMulti-protocol radio frequency identification transponder tranceiverUS7890080 *Feb 24, 2010Feb 15, 2011Broadcom CorporationMulti-protocol radio frequency identification transceiverUS8064873 *Jan 28, 2011Nov 22, 2011Broadcom CorporationMulti-protocol RF transceiverUS8125288Apr 19, 2007Feb 28, 2012Hewlett-Packard Development Company, L.P.Method for modulating a signalUS8417195Sep 8, 2006Apr 9, 2013Magellan Technology Pty LimitedMethod and apparatus adapted to transmit dataUS20090042515 *Jul 29, 2008Feb 12, 2009Thomas OstertagTransponder circuitWO2007030864A1 *Sep 8, 2006Mar 22, 2007Magellan Tech Pty LtdA method and apparatus adapted to transmit data* Cited by examinerClassifications U.S. Classification340/10.1, 340/10.2, 342/30, 340/10.51, 340/10.5, 340/13.1, 340/13.37International ClassificationG06K7/00, H04B5/02, G06K19/07, H04B1/59, G06K17/00Cooperative ClassificationG06K7/0008European ClassificationG06K7/00ELegal EventsDateCodeEventDescriptionJan 26, 2012FPAYFee paymentYear of fee payment: 8Feb 7, 2008FPAYFee paymentYear of fee payment: 4Jun 22, 2000ASAssignmentOwner name: STMICROELECTRONICS S.A., FRANCEFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WUIDART, LUC;BARDOUILLET, MICHEL;ENGUENT, JEAN-PIERRE;REEL/FRAME:010877/0571;SIGNING DATES FROM 20000427 TO 20000428Apr 5, 2000ASAssignmentOwner name: MOLEX INCORPORATED, ILLINOISFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ANDO, SHIGERU;HOSHIKAWA, SHIGEYKI;NODA, ATSUHITO;REEL/FRAME:010744/0053Effective date: 20000322RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google