Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
  • H04L27/04—Modulator circuits; Transmitter circuits
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
  • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
  • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
  • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
  • H04L25/40—Transmitting circuits; Receiving circuits
  • H04L25/49—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
  • H04L25/40—Transmitting circuits; Receiving circuits
  • H04L25/49—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems
  • H04L25/4906—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems using binary codes
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
  • H04L27/20—Modulator circuits; Transmitter circuits
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
  • H04L27/20—Modulator circuits; Transmitter circuits
  • H04L27/2032—Modulator circuits; Transmitter circuits for discrete phase modulation, e.g. in which the phase of the carrier is modulated in a nominally instantaneous manner
  • H04L27/2035—Modulator circuits; Transmitter circuits for discrete phase modulation, e.g. in which the phase of the carrier is modulated in a nominally instantaneous manner using a single or unspecified number of carriers
  • H04L27/2042—Modulator circuits; Transmitter circuits for discrete phase modulation, e.g. in which the phase of the carrier is modulated in a nominally instantaneous manner using a single or unspecified number of carriers with more than two phase states
  • H04L27/2046—Modulator circuits; Transmitter circuits for discrete phase modulation, e.g. in which the phase of the carrier is modulated in a nominally instantaneous manner using a single or unspecified number of carriers with more than two phase states in which the data are represented by carrier phase
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
  • H04B5/70—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes
  • H04B5/72—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes for local intradevice communication

Definitions

• the present invention relates to electromagnetic signal modulation devices for non-contact transmitting / receiving devices for transmitting electromagnetic signals to non-contact portable objects, and particularly to a method and device for amplitude modulation of a signal. electromagnetic emitted by a contactless transmission / reception system.
• the exchange of information between a contactless object and a contactless transmission / reception device is generally carried out by electromagnetic coupling at a distance between a first antenna located in the contactless transmission / reception device and a second antenna. antenna housed in the contactless object.
• the portable object is provided with an electronic module comprising the second antenna connected to an electronic chip which contains, inter alia, a radio frequency (RF) part, a microprocessor and / or a memory in which the information to be supplied is stored.
• RF radio frequency
• the contactless object can be of different types such as an access ticket, a card in credit card format, an electronic passport, etc.
• Data transmissions between the contactless transmission / reception system commonly referred to as a coupler or reader and contactless objects are subject to ISO standards.
• the ISO 14443 standard concerns the transmission of data by radio communication between a smart card and a reader and vice versa.
• This standard covers two transmission protocols known as Type "A" transmission protocol and "B" type transmission protocol.
• These two non - contact data transmission protocols A and B differ in the type of modulation used for Radio Frequency (RF) communication between the reader and the card on the one hand, and between the card and the reader on the other hand.
• RF Radio Frequency
• RF controller radio frequency controller
• the 10% partial modulation is trickier to obtain.
• the RF controller most often carries out this modulation between 0% and 10% by varying the impedance of its output stage according to two values.
• the impedance of the output stage of the RF controller of the transmission / reception device must be adapted to the impedance of the antenna located downstream of the controller so that the total impedance of the transmission / reception device varies. in 2 values such that the radiated signal is modulated to 0% and 10%. Therefore, the impedance values of the output stage of the controller must be adjusted according to the antenna and the environment of the reader, which is a disadvantage.
• the 10% modulation must be as stable as possible so as not to leave the authorized range of 8 to 14% and this, in the presence of any type of non-contact portable object so whatever the load.
• the total impedance is a function of the impedance of the controller, the impedance of the antenna, the variable coupling according to the distance between the antenna of the card and the antenna of the transmitting / receiving device and the impedance of the card. Consequently, a card placed in the RF field radiated by the contactless transmission / reception device causes a modification of the impedance of the antenna of the transmitting / receiving device and of the total impedance and therefore a variation of the modulation rate.
• a disadvantage is that at each antenna configuration, the user must make an adjustment to adjust the impedance levels of the output stage of the RF controller to obtain a 10% modulation acceptable by the standard. This also has the drawback of making the antenna of the transmitting / receiving device and the RF controller indissociable. Solutions exist to make the 10% modulation constant, consisting of adding amplification stages having a fixed output impedance that is not sensitive to downstream impedance variations induced by the load variations. The realization of such systems is complex. In addition, these amplification stages, when they are linear consume a lot.
• the object of the invention is to provide a partial amplitude modulation method at a modulation rate of between 8% and 14% of a carrier wave emitted by a contactless transmission / reception device. whose modulated amplitude does not vary as a function of the impedance of the transmitting antenna nor does it vary in the presence of the non - contact portable object communicating with the contactless transmission / reception device.
• the object of the invention is therefore a method of partially modulating the amplitude of a carrier wave at a rate of between 8% and 14%, the carrier wave being emitted by a transmission / reception device without contact. for remotely exchanging data with a contactless portable object.
• the process consists of:
• Another object of the invention is a non-contact transmission / reception device for remotely exchanging data with a non-contact portable object comprising a radio frequency controller delivering two symmetrical digital waves Tx1 and Tx2 from a digital signal.
• 13.56 MHz input transmitted by a clock means of phase shift of the two signals with respect to each other by 180 degrees when there is no information to be transmitted (state of rest) of the non-contact transmission / reception device to the non-contact portable object, means for phase shifting the two signals with respect to each other by an additional angle ⁇ in absolute value when there is information to be transmitted from the contactless transmission / reception device to the non-contact portable object (modulated state), filtering means of the signals Tx1 and Tx2, means for adding the two filtered signals Txlf and Tx2f so as to obtain Antenna level a resulting amplitude modulated signal at a modulation rate of between 8% and 14%.
• the method according to the invention and its associated device have the advantage of delivering signals under a constant impedance, and therefore a stable amplitude modulation in operation, whatever the type of antenna of the transmission device. contactless reception. In this way, at each antenna configuration, the user does not need to make an adjustment to adjust the impedance levels of the output stage of the RF controller to obtain a 10% acceptable type modulation by Standard. This has the advantage of separating the antenna and the RF controller from the transmission / reception device without contact and thus to make them independent of one another.
• the method according to the invention and its associated device have the advantage of allowing insertion between the RF controller and the filtering stage and adaptation of digital type amplification systems, simpler and requiring less energy. than linear amplifiers. In fact, the amplitude modulation information transmitted at this level by the phase of the signals Tx1 and Tx2 is not affected by the crossing of these amplification systems.
• FIG. 1 represents a general schematic block diagram of a contactless transmission / reception device.
• FIG. 2 represents the signals at the output of the radio frequency controller of the non-contact transmission device according to the invention
• FIG. 3 represents a schematic block diagram of the first embodiment of the RF controller of the contactless transmission device according to the invention
• FIG. 4 represents a schematic block diagram of the second embodiment of the RF controller of the contactless transmission device according to the invention
• FIG. 5 shows a schematic block diagram of the third embodiment of the contactless transmission device according to the invention outside an existing RF controller.
• the reader 10 comprises a radio frequency controller (RF controller) 11 comprising 2 output ports delivering a radio frequency signal to a transmitting antenna 14 intended to communicate with a non-contact type contactless object of the contactless card type.
• the RF controller is an electronic circuit for controlling and controlling the reader. It delivers a signal in the form of two digital signals Tx1 and Tx2 at the frequency 13.56 MHz.
• the two emitted signals are modulated in phase by the RF controller before being transmitted to the filtering and matching stage 13.
• the filtering and adaptation means are example of inductances and capacitors.
• the filtered signals Txlf and Tx2f are thus exploitable by the antenna 14 where they are added.
• the modulation of the resulting radiated signal at the level of the antenna 14 is made according to the modulation standard of the type B transmission protocol. According to this protocol, the resulting signal, also called carrier wave, emitted by the transmitting / receiving device contactless is amplitude modulated at 10%.
• the authorized limits ranging from 8% to 14% according to the standard governing this modulation, the value chosen for the device according to the invention lies within this range and preferably is equal to or close to the middle value of 11%.
• the modulated state corresponds to the transmission of the data 0 (zero).
• the resulting radiated signal at the antenna After passing through the filtering and matching stage 13 and in the antenna 14, the resulting radiated signal at the antenna has amplitude a in the idle state and b in the modulated state.
• the modulation rate m of the carrier wave radiated by the antenna follows the following formula as specified in ISO 14443-2:
• Tx1 and Tx2 of amplitude Considering the emitted digital signals Tx1 and Tx2 of amplitude equal to 1, they can be decomposed according to the Fourrier series for a square signal into a sum of a principal harmonic (txlf and Tx2f) and secondary harmonics according to the formula next :
• Txlf decomposed according to the preceding formula gives:
• Tx2 and Tx1 are out of phase by a non-zero angle ⁇ , the resulting signal is:
• Txlf - Tx2f 2 - ⁇ cos-2 + -2) /
• the amplitude of the resulting signal is therefore equal to b - cos-.
• the resulting signal at the antenna is modulated in amplitude at a modulation rate m depending on the additional phase shift angle ⁇ .
• the additional phase angle ⁇ must be equal to 70 degrees.
• the additional phase angle ⁇ is necessarily between 63.2 degrees and 82.1 degrees.
• the additional phase angle ⁇ is equal to 73.4 degrees which corresponds to a modulation rate equal to 11%.
• the additional phase shift ⁇ is obtained according to different embodiments.
• the modulation means are included in the RF controller.
• the additional phase shift is generated by delay within the radio frequency controller circuit.
• the RF controller circuit 30 of the reader comprises a clock 31 which generates a signal at a frequency of 13.56 MHz. The signal passes through an inverting logic gate 33 and a non-inverting logic gate 35 so that two 180-degree inverted paths are created.
• the signals coming from the two channels are delayed, that is to say, of identical duration T3 for the two channels, which preserves the inversion at 180 degrees, that is respectively of a duration T1 and a duration T2 in order to obtain an additional phase angle ⁇ of 73.4 degrees.
• the different delays are selected by two switches 37 and 38 controlled by the transmitted data signal 32. T3 delays are selected when the transmitted signal is at rest (data transmission 1). The delays T1 and T2 are selected when the transmitted signal transmits the data 0.
• the duration of a period corresponding to a phase shift of 360 degrees, we deduce that for an additional phase angle ⁇ of 73, 4 degrees corresponds to a duration of 15 ns (nanoseconds).
• the signal Tx2 must be delayed with respect to Txl by a duration of between 12.9 ns and 16.8 ns. It is also possible to delay Tx1 with respect to Tx2.
• the absolute value of the delay between the two signals must be between 12.9 ns and 16.8 ns and preferably equal to 15 ns.
• the two signals Tx1 and Tx2 thus modulated in phase make it possible to obtain amplitude modulation of the resulting signal at the level of the antenna according to the 10% modulation standard of the type B transmission protocol.
• the additional phase shift is generated by multiplication / division of the 13.56 MHz input signal generated inside the RF controller.
• the RF controller 40 comprises a clock 41 which generates an input signal at a frequency of 13.56 MHz.
• the signal transmitted at 13.56 MHz passes into a frequency multiplier circuit 44 and then into a frequency divider circuit 46.
• the division by n of a periodic signal of frequency f makes it possible to obtain n signals shifted by 360 / n degrees. It has been seen that in order to obtain a modulation rate m of between 8% and 14%, the additional phase angle ⁇ must be included in absolute value between 63.2 degrees and 82.1 degrees.
• the phase shifts between the two signals TX1 and TX2 essential to the object of the invention must be on the one hand 180 degrees, and on the other hand be between 180 ° + 63 ° and 180 ° ° + 82 ° be between 180 ° - 82 ° and 180 ° - 63 °.
• the multiplier circuit 44 multiplies the input signal at the frequency of 13.56 MHz by n, then the divider circuit 46 divides the signal of frequency n ⁇ 13.56 MHz into n signals at 13.56 MHz out of phase by 360 ° / n, which will be named P0 to P (nl).
• P0 to P (nl) the divider circuit 46 divides the signal of frequency n ⁇ 13.56 MHz into n signals at 13.56 MHz out of phase by 360 ° / n.
• phase-shifted signals of 180 degrees and those having the additional phase shift of ⁇ in absolute value are accessible on the same device.
• n is even and the smallest value of n satisfying this criterion is 10.
• the phase difference between the two signals must be equal to 180 degrees, so the two selected signals will be two Px signals. and P (x + n / 2), whose phase difference is equal to 180 degrees.
• the two signals When there is no information to be transmitted from the reader to the contactless portable object (data transmission 0), the two signals will be chosen such that their phase difference is between 98 degrees and 117 degrees. , or between 243 degrees and 263 degrees, so as to obtain a modulation modulated amplitude signal of between 8% and 14%.
• the selected signals will be two signals Py, and optionally P (y + n / 2 + c) or P (y + n / 2 - c) with n even such that the additional phase difference ⁇ introduced by c (integer) is included in absolute value between 63 degrees and 82 degrees.
• the additional phase angle ⁇ is equal to 72 degrees which corresponds to a modulation rate of 10.53%, therefore within the range tolerated by the standard.
• the multiplier circuit 44 multiplies the input signal at the frequency of 13.56 MHz by 10 then the divider circuit 46 divides the frequency signal 135.60 MHz (10x13.56 MHz) into 10 so as to obtain 10 signals shifted in phase of 36i degrees.
• a phase signal P0 0 degrees
• a phase signal PI 36 degrees
• a phase signal P3 108 degrees
• a phase signal P4 144 degrees
• a phase signal P5 180 degrees
• a phase signal P6 216 degrees
• a phase signal P7 252 degrees
• a phase signal P8 288 degrees
• the two selected signals Tx1 and Tx2 will be selected by switches 47 and 48 such that their phase difference will be equal to 252 degrees (180 ° + 72 °) of to obtain a modulation modulated amplitude signal equal to 10.53%.
• the choice of the two signals Tx1 and Tx2 when there is information to be transmitted to the card so in the presence of the data 0 Txl advance of 36 degrees and delays Tx2 by 36 degrees with respect to the signals Txl and Tx2 when n ' There is no information to be transmitted or the data to be transmitted is 1.
• the multiplier circuit 44 can be made by a phase-locked loop called "PLL stage".
• the two out-of-phase signals Tx1 and Tx2 make it possible to obtain a modulation of the resulting signal at the level of the antenna in compliance with the 10% modulation standard of the type B transmission protocol.
• the first two embodiments are realized by means of modulations implemented inside the RF controller, and integrable in the silicon of a
• the modulation rate of 10% guarantees the construction of the RF controller since the modulation device described is integrated directly into the RF controller.
• the two signals Tx1 and Tx2 at the output of the RF controller are out of phase by an angle of 180 degrees at the idle state and 180 ° + ⁇ or 180 ° - ⁇ at the modulated state.
• modulation means can be realized outside an existing RF controller 51 as illustrated in FIG. 5 and according to a third embodiment of the invention.
• the modulation type B generated by modulating the output impedance Tx1 and TX2 of the controller is not used.
• the type B data to be transmitted is routed to an output port of the RF controller.
• the partial modulation method is implemented in an external circuit at the output of the RF controller circuit 51.
• the RF controller circuit 51 generates the digital radio frequency signals Tx1 and Tx2 at the frequency of 13.56 MHz. and delivers the B-type data 52 to be transmitted on .
• the TX2 signal is usually available already 180 degrees out of phase with TX1 on the current RF controllers.
• the signal Tx2 goes into a circuit 53 which makes it possible to delay the signal Tx2 by a duration T1 with respect to Tx2.
• the TX2 signal or the delayed signal TX2 is selected by a switch 55 as a function of the data item 52 to be transmitted.
• a buffer circuit 54 is added downstream of the switch.
• the duration of a period corresponding to a phase shift of 360 degrees we deduce that for an additional phase angle ⁇ of 73.4 degrees, corresponding to the midpoint of the range [8%; 14%] of the allowed modulation rate, corresponds to a duration of 15 ns (nanoseconds).
• the signal Tx2 must be delayed with respect to Txl by a duration of between 12.9 ns and 16.8 ns.
• the two out - of - phase signals Txlm and Tx2m obtained at the output of the device make it possible, after passage through the filtering and adaptation stage, to obtain a modulation of the resulting signal at the level of the antenna according to the 10% modulation standard.
• Type B transmission protocol The embodiment described in FIG. 5 of the third embodiment is based on one of the simplest architectures for obtaining the method and the device according to the invention.
• This embodiment generates parasitic phase jumps of the order of 18 degrees to 10% modulation transitions of the 13.56 MHz frequency signal radiated by the antenna.
• phase jumps have a sufficiently small amplitude not to affect the operation of the internal clock of the presented non-contact objects or reader equipped with this device.

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• 2011
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• 2012
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  • 2012-05-02 MX MX2013012394A patent/MX2013012394A/es active IP Right Grant
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