HK1195648B - Method and device for modulating the amplitude of an electromagnetic signal transmitted by a wireless transceiver - Google Patents

Description

Amplitude modulation method and device for electromagnetic signals transmitted by non-contact transceiving system

Technical Field

The present invention relates to an electromagnetic signal modulation apparatus for a contactless transmitting and receiving apparatus to transmit an electromagnetic signal to a contactless portable object. And more particularly, to a method and apparatus for amplitude modulation of electromagnetic signals transmitted by a contactless transmission/reception system.

Background

Information is generally exchanged between the contactless object and the contactless transmitting and receiving device by: a remote electromagnetic coupling is made between a first antenna on the contactless transceiver device and a second antenna on the contactless object. The portable object is provided with an electronic module with a second antenna connected to an electronic chip containing a radio frequency part (RF), a microprocessor and/or a memory, etc. The memory stores therein information to be provided to the contactless transceiver device, and necessary logic functions for editing the information to be transmitted and processing the received information.

Non-contact objects can be of various types: such as a pass, a card in the form of a credit card, an electronic passport, etc. A contactless transmission and reception system is generally called a coupler or a reader, and data transmission between a contactless object and the system conforms to ISO standard regulations. Among the current standards, the standard ISO14443 relates to the transmission of data between a chip card and a reader by radio communication with each other. The standard contains two transport protocols called type a transport protocol and type B transport protocol. The A, B two types of contactless data transfer protocols differ in the type of modulation used for Radio Frequency (RF) communication between readers and cards, and between cards and readers. For transmitting data to the contactless card, the carrier wave is 100% modulated in the type a transmission protocol, and 10% modulated in the type B protocol.

Such 10% modulation is also used for type B' contactless object readers (type B modulation ISO14443-2 of the Innovatron proprietary protocol), Sony Felica, ISO18092(NFC) and ISO 15693.

These two types of modulation are typically implemented inside a radio frequency controller (RF controller) integrated circuit located in the contactless transceiver device.

The 10% partial modulation requires more skill as opposed to the 100% modulation typically obtained by temporarily stopping the carrier generator of the RF controller. In fact, the RF controller more often varies its output stage impedance according to two values, thereby achieving such 0% -10% modulation. However, the output stage impedance of the RF controller of the transceiving device needs to be matched to the antenna impedance of the controller back end, so that the total impedance of the transceiving device varies according to two values such that the transmitted signal is modulated by 0% and 10%. Therefore, the impedance value of the output stage of the controller needs to be adjusted according to the antenna and the reader environment, which brings inconvenience.

Furthermore, the 10% modulation should be as stable as possible, not exceeding the allowable range of 8% to 14%, which is applicable to any type of contactless portable object, no matter how heavy the load is. With a card, the total impedance varies with the following factors: controller impedance, antenna impedance, coupling conditions that vary with the distance between the card antenna and the transceiver antenna, impedance of the card. Thus, a card placed in the RF field emitted by the contactless transceiver device may change the antenna impedance and the total impedance of the transceiver device, thereby changing the modulation rate. One troublesome fact is: each time the antenna is configured, the user needs to readjust to modify the RF controller output stage impedance level to achieve a standard-compliant 10% modulation. Another inconvenience is that the transceiver equipment is not separable from the RF controller. A solution to keep the 10% modulation constant is now to add an amplifier stage with a constant output impedance that is insensitive to back-end impedance variations caused by load variations. The implementation of such a system appears to be complex. Furthermore, the amplification stage consumes a lot of power if it is linear.

Disclosure of Invention

Therefore, the present invention aims to provide a partial amplitude modulation method with a modulation rate of 8% to 14%, which modulates a carrier wave transmitted by a non-contact transceiver device, and the modulated amplitude does not change with the impedance of a transmitting antenna and also does not change due to the communication between a non-contact portable object and the non-contact transceiver device.

The invention aims to provide a method for modulating the amplitude part of a carrier wave with a modulation rate of 8-14%, wherein the carrier wave is sent by a non-contact transceiving device and is used for remotely exchanging data with a non-contact portable object. The method comprises the following steps:

a) emitting two digital radio frequency signals Tx1(20) and Tx2(22) with the frequency of 13.56 MHz;

b) when there is no information to be transmitted from the contactless transmitting-receiving device to the contactless portable object (idle state), the second signal Tx2 is phase-shifted by 180 degrees with respect to the first signal Tx 1;

c) when there is information to be transmitted from the contactless transmitting-receiving device to the contactless portable object (modulation state), the two signals Tx2 are phase-shifted with respect to Tx1 or Tx1 with respect to Tx2 by an additional phase difference

d) Passing the digital signal through a filtering and matching stage (13);

e) the first phase modulated and filtered signal and the second phase modulated and filtered signal (Tx1f and Tx2f) are added and an amplitude modulated transmit composite signal is obtained.

Another object of the invention is a contactless transceiver device for exchanging data remotely from a contactless portable object, comprising a radio frequency controller emitting two symmetrical digital signals Tx1 and Tx2 based on a clock-emitted input signal of 13.56MHz, when there is no information to be transmitted from the contactless portable objectPhase shifting means for shifting the phase of one of said two signals by 180 degrees with respect to the other signal when the transceiving device is transmitting to the contactless portable object (idle state), and for shifting the phase of one of said two signals by an absolute value with respect to the other signal when there is information to be transmitted from the contactless transceiving device to the contactless portable object (modulated state)Additional angular phase shifting means of (a), filtering and matching means of said two signals Tx1 and Tx 2; for adding the two filtered signals Tx1f and Tx2f to obtain an amplitude modulated composite signal at the antenna with a modulation rate between 8% and 14%.

The advantage of the method according to the invention and the related device is that the signal is emitted with a constant impedance, so that a stable amplitude modulation is achieved in operation, regardless of the type of antenna of the contactless transceiver device. In this way, the user does not need to adjust the impedance level of the output stage of the calibration RF controller each time the antenna is configured in order to obtain a standard-compliant 10% type modulation. This has the advantage that the antenna can be separated from the RF controller of the contactless transceiver device, so that they are independent of each other.

The method and the related equipment thereof have the following advantages: allowing to insert a digital type amplification system between the RF controller and the filtering and matching stage, simpler and less power consuming than a linear amplifier. In fact, the phase amplitude modulation information of the signals Tx1 and Tx2 transmitted to this stage is not affected by passing through the amplification system.

Drawings

The objects, aspects and features of the present invention will become more apparent upon reading the following description and the accompanying drawings referred to therein, wherein:

fig. 1 shows a general schematic block diagram of a contactless transceiver device.

Fig. 2 shows output signals of a radio frequency controller of a contactless transceiver device according to the present invention.

Fig. 3 shows a schematic block diagram of a first embodiment of an RF controller of a contactless transceiver device according to the present invention.

Fig. 4 shows a schematic block diagram of a second embodiment of an RF controller of a contactless transceiver device according to the present invention.

Fig. 5 shows a schematic block diagram of a third embodiment of a contactless transceiver device according to the invention, outside an existing RF controller.

Detailed Description

Hereinafter, the contactless transmitting and receiving device according to the present invention is referred to as a reader. According to fig. 1, the reader 10 comprises a radio frequency controller (RF controller) 11, the radio frequency controller 11 having 2 output ports, which output ports send radio frequency signals to a transmitting antenna 14, which transmitting antenna 14 is used for communicating with a contactless portable object of the contactless card type. The RF controller is the reader's monitoring and control electronics, transmitting two digital signals Tx1 and Tx2 at a frequency of 13.56 MHz. To transmit data from the reader to the card, the two signals sent are phase modulated by the RF controller before being passed to the filtering and matching stage 13. The filtering and matching means are for example inductors and capacitors. Thus, the filtered signals Tx1f and Tx2f are available for use by the antenna 14, where they are summed. The modulation of the transmitted signal generated at the antenna 14 is performed according to the modulation standard of the type B transmission protocol. According to this protocol, the composite signal, also called carrier, emitted by the contactless transceiver device is 10% amplitude modulated. The permissible range is 8% to 14% depending on the standard for which the modulation is applied, so that the device according to the invention takes values within this range, preferably equal to or close to the median value of 11%.

Two signals Tx1 and Tx2 from the two output ports of the RF controller are shown in fig. 2. These two signals are rectangular binary digital signals with a constant duty cycle equal to 50%. In the idle state, i.e. when there is no information to transmit, the two signals are 180 degrees out of phase, as shown, Tx2= -Tx 1. The idle state corresponds to transmitting data 1.

When transmitting information to the card, the RF controller toggles an absolute value between the two signals Tx1 and Tx2, corresponding to the modulation stateSo as to transmit a signal with a modulation rate of 10%. The modulation state corresponds to transmission data 0 (zero). After passing through the filtering and matching stage 13 and the antenna 14, the transmitted signal generated by the antenna has an amplitude a in the idle state and an amplitude b in the modulated state. The modulation rate m of the carrier transmitted by the antenna is given in the following formula defined by the standard ISO 14443-2:

m=(a-b)/(a+b)

considering that the emitted digital signals Tx1 and Tx2 have an amplitude of 1, the two signals can be decomposed into a sum of first harmonics (Tx1f and Tx2f) and second harmonics according to the fourier series for a square wave signal, and the formula is as follows:

after passing through the filtering and matching stage, the second harmonic is cancelled by the stage. When Tx2 and Tx1 are out of phaseDegree, and amplitude equal to 1, Tx1f decomposed according to the previous formula:

tx2f is decomposed according to the following equation:

thus, the composite signal is:

when there is no data to transmit, i.e., in an idle state, Tx2= -Tx1 andthe composite signal is:

thus, the amplitude of the composite signal is equal to:

when there is data to transmit, i.e. in the modulated state, Tx2 and Tx1 are out of phase by a non-zero angleThe composite signal is:

thus, the amplitude of the composite signal is equal to:

according to the calculation formula of the modulation rate:

m=(a-b)/(a+b)

the following can be obtained:

according to this formula, the composite signal at the antenna is amplitude modulated with a modulation rate m that depends on the additional phase difference

Additional phase angle difference in order to obtain nominal modulation rate m =10% for type B transmission protocols according to standard 14443Should be equal to 70 degrees. According to preferred embodiments of the present invention, since the modulation rate is 8% to 14%, a phase angle difference is addedMust be between 63.2 degrees and 82.1 degrees. The additional phase angle difference is preferably equal to 73.4 degrees, corresponding to a modulation rate of 11%.

Additional phase differenceAccording to different embodiments. According to a first and a second embodiment of the invention, the modulation means are comprised in an RF controller. According to a first embodiment of the invention, the additional phase difference is generated by a delay inside the radio frequency controller. As shown in fig. 3, the RF control circuitry 30 of the reader includes a clock 31 which generates a signal having a frequency of 13.56 Hz. The signal passes through the not gate 33 and the logic gate 35, thereby generating two paths 180 degrees out of phase. The signals coming out of these two paths are then delayed: the two paths are delayed by the same time length T3, thereby keeping 180 degree inverse or delayed by one duration T1 and one duration T2, respectively, to obtain an additional phase angle difference of 73.4 degreesThe different delays are selected by two switches 37, 38, the two switches 37, 38 being controlled by the transmitted data signal 32. When the transmitted signal is idle (data 1 is transmitted), the delay T3 is selected. When the transmitted signal transmits data 0, delays T1 and T2 are selected.

The period of the transmitted signal at frequency 13.56MHz is: t is 1/f 73.7 ns. The duration of one cycle corresponds to a phase difference of 360 degrees, from which it can be deduced that: additional phase angle difference of 73.4 degreesCorresponding to a duration of 15ns (nanoseconds). Therefore, the signal Tx2 should be delayed by one duration T2-T1-15 ns with respect to Tx1 in order to obtain a modulation rate of 11%. To achieve a modulation rate of 8% to 14%, the signal Tx2 should be delayed with respect to Tx1 by a duration of 12.9ns to 16.8 ns. Tx1 may also be delayed relative to Tx 2. The absolute value of the delay between these two signals should be 12.9ns to 16.8ns, preferably equal to 15 ns.

By thus phase-modulating the two signals Tx1 and Tx2, a composite signal amplitude-modulated according to the 10% modulation standard of the type B transmission protocol is made available at the antenna.

According to a second embodiment of the invention, the additional phase difference is generated by multiplying/dividing an input signal of 13.56MHz generated inside the RF controller. As shown in fig. 4, the RF controller 40 includes a clock 41, and the clock 41 generates an input signal having a frequency of 13.56 MHz. The emitted 13.56MHz signal passes through a frequency multiplication circuit 44 and then a frequency divider circuit 46. A periodic signal of frequency f divided by n can result in n signals shifted by 360/n degrees. It has been observed that in order to obtain modulation rates m of 8% to 14%, an additional phase angle difference is addedShould have an absolute value between 63.2 degrees and 82.1 degrees.

Rounding the angles, the phase difference between the two signals Tx1 and Tx2, which are the core of the present disclosure, should be 180 degrees in one case and 180 ° +63 ° + 180 ° +82 ° in the other case, or 180 ° -82 ° -180 ° -63 °.

The multiplier circuit 44 multiplies the input signal having a frequency of 13.56MHz by n, and the frequency divider circuit 46 divides the signal having a frequency of nx13.56mhz into n signals of 13.56MHz with a phase difference of 360o/n, hereinafter referred to as P0 to P (n-1). Of these phase-shifted signals, two signals whose phase difference satisfies the requirement may be selected according to the state of data to be transmitted. This selection is effected by the changeover switch circuits 47 and 48, the changeover switch circuits 47 and 48 being controlled by the data 42 to be transmitted.

It is confirmed that for all even n there are signals at the divider 46 that are 180 degrees out of phase.

With additional phase difference having absolute value within the range of desired valuesIs obtained for a particular value of n, the first value being 5.

For ease of implementation, the sum of the signals 180 degrees out of phase has an absolute valuePreferably the signals of the additional phase difference of (2) are obtained in the same device. In this case, the minimum even number n satisfying this condition is 10.

When there is information to be transmitted from the reader to the non-contact portable object (transmission data 1), the phase difference between the two signals should be equal to 180 degrees, and therefore, the two signals selected are the signals Px and P (x + n/2), the phase difference of which is equal to 180 degrees.

When there is no information to be transmitted from the reader toWhen the portable object is not in contact (data 0 is transmitted), two signals having a phase difference of between 98 degrees and 117 degrees or between 243 degrees and 263 degrees should be selected so as to obtain an amplitude modulation signal having a modulation rate of between 8% and 14%. The two signals selected are Py and one of P (y + n/2+ c) or P (y + n/2-c), where n is an even number, such that c (integer) causes an additional phase differenceThe absolute value is between 63 degrees and 82 degrees.

By selecting the values of x, y, c that satisfy the above conditions, it is possible in any case to send on the antenna an amplitude-modulated carrier wave between 8% and 14% depending on the modulation rate of the data to be transmitted.

However, an incorrect selection of the above values may cause interfering phase jumps on the generated transmit carrier during the modulation transition phase, which, if large, may cause problems for the communication. In fact, the frequency of the carrier wave 13.56MHz is used as a reference clock for the contactless object.

Only x, y, z values which satisfy the following condition do not produce any interfering phase jitter in the amplitude modulation transition phase:

x=y+c

or

x=y-c

According to a preferred embodiment of the invention, the phase angle difference is addedEqual to 72 degrees, corresponding to a modulation rate of 10.53% and therefore within the interval permitted by the standard. According to a preferred embodiment, the frequency of the input signal, 13.56, is multiplied by a factor n =10 and divided. In this case, the multiplier circuit 44 multiplies the input signal with a frequency of 13.56MHz by 10, and then the divider circuit 46 divides the signal with a frequency of 135.60MHz (10 × 13.56mhz) by 10, resulting in 10 signals that are phase shifted by 36 degrees:

a signal with phase P0 ═ 0 degrees

One signal with phase P1 equal to 36 degrees

One signal with phase P2 equal to 72 degrees

A signal with phase P3 ═ 108 degrees

A signal with phase P4 equal to 144 degrees

A signal with phase P5 equal to 180 degrees

A signal with phase P6 ═ 216 degrees

A signal with a phase P7 of 252 degrees

288 degrees of phase P8

A signal with a phase P9 ═ 324 degrees

Of these phase shifted signals, only two signals having a phase difference satisfying the requirement need to be selected from them according to the data 42 to be transmitted. This selection is achieved, for example, by switching the switching circuits 47 and 48. Specifically, when there is no information to be transmitted (transmission data 1), the phase difference between the two signals should be equal to 180 degrees, and therefore, two signals selected from the 10 signals P0 to P9 phase-shifted by 36 degrees are, for example, two signals whose phases P7-252 degrees and P2-72 degrees. Also, when there is information to be transmitted to the card, the following two signals Tx1 and Tx2 should be selected by the changeover switches 47 and 48: the phase difference is equal to 252 degrees (180 ° +72 °), so as to obtain an amplitude-modulated signal with a modulation rate equal to 10.53%. The two signals Tx1 and Tx2 selected are, for example, signals of phases P1=36 degrees and P8=288 degrees. When there is information to be transmitted to the card, i.e., data 0, the signals Tx1 and Tx2 are selected to advance Tx1 by 36 degrees and retard Tx2 by 36 degrees relative to the signals Tx1 and Tx2 when there is no information to be transmitted or the data to be transmitted is 1. This choice ensures that the composite signal is not phase shifted at the transition time of the amplitude modulation, in other words, that there is no parasitic phase rotation on the carrier wave transmitted by the antenna. The multiplier circuit 44 may be implemented by a phase-locked loop known as a "PLL stage".

By having the two signals Tx1 and Tx2 so out of phase, it is possible to obtain a modulation of the composite signal at the antenna which complies with the 10% modulation standard of the type B transmission protocol.

The first two embodiments are implemented by a modulation means installed inside the RF controller, which may be integrated in the silicon of the RF controller circuitry. In this way, a modulation ratio of 10% is guaranteed when manufacturing the RF controller, since the modulation means are directly integrated in the RF controller. Thus, the two output signals Tx1 and Tx2 of the RF controller are 180 phase difference in idle state and 180 phase difference in modulation stateOrThe phase angle.

However, according to the third embodiment of the present invention, a similar modulation means may be implemented outside the existing RF controller 51, as shown in fig. 5. In this case, the B-type modulation resulting from the impedance modulation of the controller outputs Tx1 and Tx2 is not utilized. Type B data to be transmitted is directed to an output port of the RF controller. According to a third embodiment of the invention, part of the modulation method is implemented in an external circuit at the output of the RF controller circuit 51. Therefore, whether or not the additional phase difference is generated is decided according to the data to be transmitted delayed due to the electronic circuit 50 as shown in fig. 5. The RF controller circuit 51 generates two digital radio frequency signals Tx1 and Tx2 at a frequency of 13.56MHz, and transmits the type B data 52 to be transmitted on one of its output ports. The signal Tx2 is typically available on current RF controllers, which has been 180 degrees out of phase with respect to Tx 1. The signal Tx2 passes through the circuit 53, which circuit 53 may delay the signal Tx2 by a duration T1 relative to Tx 2. The signal Tx2 or the delayed signal Tx2 is selected by a switch 55 in accordance with the data 52 to be transmitted. In order to ensure a stable and as small as possible output impedance for the device output signals TX1m and TX2m, a buffer circuit 54 is added at the rear end of the switch. Is sent outThe signal of frequency 13.56MHz has a period T ═ 1/f =73.7 ns. The duration of one cycle corresponds to a phase difference of 360 degrees, from which it follows: for the interval corresponding to the allowable modulation rate [8%;14% ]]73.4 degrees additional phase angle difference of the median ofCorresponding to a duration of 15ns (nanoseconds). Therefore, the signal Tx2 should be delayed by one T1-15 ns duration with respect to Tx1 in order to obtain a modulation rate of 11%. To achieve a modulation rate of between 8% and 14%, the signal Tx2 should be delayed with respect to Tx1 by a duration of between 12.9ns and 16.8 ns.

The two signals Tx1m and Tx2m obtained at the output of the device with such a phase difference, after passing through the filtering and matching stage, make it possible to obtain at the antenna a modulated composite signal complying with the 10% modulation standard of the type B transmission protocol. The third embodiment shown in fig. 5 implements the method and apparatus according to the invention based on the simplest architecture.

This implementation produces a parasitic phase jitter of about 18 degrees during the 10% modulation transition of the 13.56MHz signal transmitted by the antenna.

The amplitude of this phase jump is small enough not to affect the internal clock operation of the contactless object used, nor the reader equipped with such a device.

Claims (15)

1. A method of partial amplitude modulation of a carrier wave at a rate between 8% and 14%, the carrier wave being emitted by a contactless transceiving device for remote data exchange with a contactless portable object,

the method is characterized by comprising:

a) emitting two digital radio frequency signals Tx1(20) and Tx2(22) with the frequency of 13.56 MHz;

b) when there is no information to be transmitted from the contactless transmitting-receiving device to the contactless portable object (idle state), the second signal Tx2 is phase-shifted by 180 degrees with respect to the first signal Tx 1;

c) when there is information to be transmitted from the contactless transmitting/receiving device to the contactless portable object (modulation state), the two signals, Tx2, are phase-shifted relative to Tx1 or Tx1 relative to Tx2 by an additional phase differenceWherein the additional phase differenceBetween 63.2 degrees and 82.1 degrees;

d) passing the digital signal through a filtering and matching stage (13);

e) the first and second phase modulated and filtered signals (Tx1f and Tx2f) are added and a composite signal is obtained that is amplitude modulated between 8% and 14%.

2. Method according to claim 1, wherein the two signals Tx1 and Tx2 are emitted in the form of two rectangular digital signals of constant duty cycle equal to 50%, the signals Tx1 and Tx2 being generated by the radio frequency controller circuit (11, 30, 40, 51) based on an input signal of 13.56MHz emitted by the clock (31, 41).

3. A method according to claim 1 or 2, wherein the amplitude modulated composite signal has a modulation rate m, m being dependent on the additional phase difference angle according to：

4. Method according to claim 1 or 2, wherein said additional phase differenceObtained by delaying the signal Tx2 by a time period T2 and the signal Tx1 by a time period T1 such that the absolute value of the difference of T2-T1 is between 12.9 nanoseconds (ns) and 16.8 ns.

5. The method according to claim 2, wherein the phase shifting steps b) and c) are obtained as follows:

multiplying the 13.56MHz input signal generated by a clock (41) of an RF controller (40) by a factor n;

dividing the signal obtained in the previous step by a factor n to obtain n signals shifted by 360/n degrees;

two signals Tx1 and Tx2 are selected from the n signals obtained in the previous step, such that Tx1 and Tx2 are 180 degrees out of phase when no information is to be transmitted from the contactless transmitting/receiving device to the contactless portable object (idle state), and the other two signals are selected to be 180 degrees out of phase when there is information to be transmitted from the contactless transmitting/receiving device to the contactless portable object (modulation state)Degree orA signal of degree.

6. The method according to claim 5, wherein the factor n is equal to 10 and the two signals Tx1 and Tx2 are selected from 10 signals P0 to P9 that are 36 degrees out of phase, so that Tx1 and Tx2 are 180 degrees out of phase when no information is to be transmitted from the contactless transceiving device to the contactless portable object, and Tx1 and Tx2 are 252 degrees out of phase when there is information to be transmitted from the contactless transceiving device to the contactless portable object.

7. The method according to claim 2, wherein the method is implemented inside the radio frequency controller circuit (11, 30, 40) of the contactless transceiver device (10).

8. Method according to claim 2, wherein the method is implemented in an external circuit (50) at the output of the radio frequency controller circuit (51) of the contactless transceiver device (10).

9. A method according to claim 3, wherein said additional phase differenceEqual to 73.4 degrees.

10. The method of claim 4, wherein the absolute value of the difference of T2-T1 is equal to 15 ns.

11. A contactless transceiving device for remotely exchanging data with a contactless portable object, comprising: radio frequency controller (11, 30, 40, 51) emitting two symmetrical digital signals Tx1 and Tx2 based on an input signal of 13.56MHz emitted by a clock (31, 41), for phase shifting one of the two signals by 180 degrees with respect to the other when no information is to be transmitted from a contactless transceiver device to a contactless portable object (idle state), and for phase shifting one of the two signals by an absolute value of one with respect to the other when information is to be transmitted from a contactless transceiver device to a contactless portable object (modulated state)Said two signals Tx1 and Tx2, means (13) for adding the two filtered signals Tx1f and Tx2f to obtain an amplitude modulated composite signal transmitted at the antenna with a modulation rate between 8% and 14%, wherein said phase shifting one of said two signals with respect to the other signal is of absolute valueThe additional angular phase shifting means of (2) comprise at least one logic delay stage (33, 53), the logic delay stage (33, 53) being adapted to delay one of said two signals with respect to the other signal by a time period T of absolute value between 12.9 nanoseconds (ns) and 16.8 ns.

12. The apparatus of claim 11, wherein the delay T is equal to 15ns in order to obtain a modulation rate of 11%.

13. Device according to any of claims 11 to 12, wherein said phase shifting means of said two signals are directly arranged in the RF controller (11, 30, 40) of the contactless transceiver device.

14. The apparatus according to any of claims 11 to 12, wherein the phase shifting means comprises a multiplier circuit (44) for multiplying the frequency of 13.56MHz of the input signal generated by the clock (41) of the RF controller (40) by a factor n, a divider circuit (46) for dividing the signal multiplied by the multiplier circuit into n signals phase-shifted by 360/n degrees, a divider circuit (46) for selecting two signals Tx1 and Tx2 from the n signals such that when no information is to be transmitted from the contactless transceiver device to the contactless portable object (idle state) Tx1 and Tx2 are 180 degrees out of phase and when information is to be transmitted from the contactless transceiver device to the contactless portable object (modulation state) two further phase differences are selectedAnd (4) a change-over switch of the signal of the degree.

15. The contactless device according to claim 14, wherein said factor n is equal to 10 and the phases of said two selected signals Tx1 and Tx2 are 72 degrees and 252 degrees when no information is to be transmitted from the contactless transceiving device to the contactless portable object (idle state) and 36 degrees and 288 degrees when there is information to be transmitted from the contactless transceiving device to the contactless portable object (modulation state).