Title of Invention

'DATA MEDIUM'

Abstract

Data medium, comprising: atteast one coil (1) for contacttessly receiving amplitude-modulated signals, a rectifier circuit (2) connected down-stream of the coil (1), a circuit arrangement (3) for processing and / or storing data, the circuit arrangement (3) has a paratley connected supply voltage regulating circuit (4), and in that a current measuring device (SME; RM, DS; SP, DS; TR, DS; Dll, D22, DS; SP1, SP2, D5) acting as an amplitude demodulator is arranged between the coit (1) and the arrangement comprising the supply voltage regulating circuit (4) and the circuit arrangement (3) for processing and / or storing data.

Full Text

DATA CARRIER FOR THE CONTACTLESS RECEPTION OF AMPLITUDE-MODULATED SIGNALS The invention relates to a data carrier with at least one coil for the contactless reception of amplitude-modulated signals, with a rectifier circuit connected downstream of the coil and with a circuit arrangement for processing and/or storing the data. Such a data carrier is at present on the market mainly in the form of a chip card and is known from German Application 196 34 134.5. In the case of the method described there for transmitting data between a terminal and a portable data carrier via a wireless electromagnetic transmission link, a 100% ASK modulation of the carrier signal takes place, as is generally customary in the case of present-day contactless transmissions such as this. Although this switching on/off of the carrier signal is relatively easy to demodulate in the data carrier, it has the disadvantage that no clock signal is available during the blanking interval. In the standardizing bodies for the contactless chip card (ISO 14443), however, the current standpoint is to use not only ON-OFF keying (OOK) but also amplitude-shift keying (ASK) with a degree of modulation of 5 to 15% for the data transmission from a writing/reading device to a card or generally to a data carrier. Such modulation is difficult to demodulate, however, since the distance between the writing/reading device and the data carrier can change greatly and, as a result, the amplitude of the received signal .is subject to fluctuations which,.are superposed on the modulation and falsify it. In addition, the circuits in the data carrier have a greatly fluctuating power consumption, which likewise has retroactive effects on the modulation. The problems referred to are particularly critical in the case of passive data carriers, which have no power supply of their own and obtain their operating energy from the signal received. It is therefore the object of the invention to specify a data carrier in which these problems are reduced or even eliminated. The object is achieved by a data carrier as claimed in claim 1. Advantageous developments are specified in the subclaims. In the case of the data carrier according to the invention, the demodulator is realized in conjunction with the power supply concept. As a first measure, the circuit arrangement has a supply-voltage control circuit connected in parallel - 2 - with it. This brings about a decoupling of the currents in the load circuit provided by the circuit arrangement and in the supply circuit provided by the coil and the rectifier. Consequently, the current in the supply circuit is only dependent on the power offered by the signal received by the coil. With a current measuring device, acting as an amplitude demodulator, for the current in the supply circuit, the amplitude modulation is registered. In a first design of the invention, a measuring resistor of which the terminals are connected to a demodulator circuit is arranged in the supply circuit. The demodulator circuit consequently evaluates the voltage drop across the measuring resistor, which is a measure of the amplitude modulation. A second design of the invention provides a current mirror circuit, the output current of which is equal or at least proportional to the current in the supply circuit and consequently to the modulation. The current mirror circuit has the advantage that the voltage drop across the diode or the diode transistor in the supply circuit depends on the current in a non-linear relationship and, in the case of great currents, increases only with the root of the current and consequently limits the voltage at the rectifier. In spite of the lower resistance of the current mirror diode in comparison with a measuring resistor, it is desirable to reduce the resistance value further. This takes place in a development according to the invention by means of a bias voltage at the gate of the current-mirror diode transistor, whereby the latter becomes more conductive. The bias voltage is advantageously chosen such that the current-mirror diode transistor is still just in saturation. A first embodiment for a bias-voltage generating circuit is realized by a voltage divider which is connected to the supply voltage, advantageously to the controlled supply voltage. In an advantageous development, the voltage divider can be designed as a filter, in order to suppress voltage fluctuations which are caused at the parallel run controller by a changing load. A further embodiment is formed by a further voltage controlling circuit. This may be connected in an advantageous way to the supply-voltage controlling circuit, in other words be supplied with power by the latter, in order in this way to supply a more stable output voltage. In a third design of the invention, the current mirror circuit is integrated into the rectifier circuit. As a result, no further voltage drops between the rectifier circuit and the load, since the current mirror circuit shares - 3 - the use of a diode already contained in the rectifier circuit. In an advantageous way, two current mirror circuits are used, since then the pulse frequency of the input current of the demodulator circuit to be connected downstream of a current mirror circuit is twice as high, whereby the filtering in the demodulator circuit is made easier. The voltage drop may also be detected and evaluated at rectifier diodes themselves. For this purpose, at least one further pair of diodes is connected in an advantageous way in parallel with a pair of diodes of the rectifier circuit leading to a supply line. The connecting point of the diodes, arranged with opposite polarity, of this further pair of diodes is connected to a first input of a demodulator circuit. The supply voltage delivered by the corresponding pair of diodes of the rectifier circuit is fed to a second input of the demodulator circuit, so that the demodulator circuit can evaluate the differential voltage. The diodes represent a non-linear resistance, the characteristic of which must be taken into consideration in the demodulation. This variant of the invention has the one advantage that no additional voltage drop occurs and the other advantage that the extension of the rectifier circuit can be carried out very simply in practice. An advantageous combination of the supply voltage control in the load circuit with the current measurement in the supply circuit is achieved in a further embodiment of the invention with a series control circuit, in which the voltage is controlled at the output of the rectifier circuit. A transistor arranged in the current path between the rectifier circuit and the supply-voltage control circuit is driven in such a way that its resistance changes according to the current in the supply circuit in such a way that the voltage drop across the transistor remains virtually constant. The control signal for the transistor is then a measure of the current in the supply circuit and consequently of the modulation. The invention is explained in more detail below on the basis of exemplary embodiments with the aid of figures, in which: Fig. 1 shows a basic representation of the data carrier according to the invention, Fig. 2 shows a basic representation of a first exemplary embodiment, Fig. 3 shows a basic representation of a second exemplary embodiment of the invention, _ 4 - Fig. 4 shows a development of the exemplary embodiment according to Fig. 3, Fig. 5 shows a further development of the embodiment according to Fig. 3, Fig. 6 shows a basic representation of a third embodiment of the invention, Fig. 7 shows a basic representation of a fourth embodiment of the invention, Fig. 8 shows a basic representation of a fifth embodiment of the invention, and Fig. 9 shows a more detailed representation of the control and demodulator circuit according to Fig. 8. According to Fig. l, a coil 1 is connected to a rectifier circuit 2, which for its part supplies a supply voltage via lines 6, 7 to a circuit arrangement 3 for processing and/or storing data. The data carrier represented in principle in Fig. 1 is intended to be able on the one hand to receive energy and data from a writing/reading device via the coil 1, the carrier signal sent from the writing/reading device being amplitude-modulated. On the other hand, it is also possible to send data from the data carrier to the writing/reading device, a loading modulation being carried out at the coil 1 for this purpose as an example and as customary at present. Since details on this are of no significance for the present invention, the circuit parts necessary for this are not represented in the figures and are also not presented any further hereafter. The circuit arrangement 3 for processing and storing data has primarily a preferably non-volatile data memory. In also comprises, however, logic circuits for processing and editing the data, in particular in order to carry out the intended task as a response to the data received. In a particularly highly developed embodiment of such a data carrier, the circuit arrangement 3 comprises a complete microcomputer. The circuit arrangement 3 described requires on the one hand as constant a supply voltage as possible, but will have a fluctuating power or current consumption, depending on the task to be achieved. Although the writing/reading device will send a signal with a constant signal output to the data carrier, the signal received there will have a fluctuating amplitude, depending on the distance of the data carrier from - 5 - the writing/reading device. These two effects are superposed on the amplitude modulation of the carrier signal and can consequently falsify the data to be received. In a way corresponding to the invention, the problem of the demodulation of the amplitude-modulated signal is solved in conjunction with the power supply concept, in particular the supply voltage stabilization. As a first measure, the circuit arrangement 3 has a supply-voltage control circuit 4 connected in parallel with it. This parallel run controller 4 carries away the higher current which is delivered by the coil 1 and the rectifier circuit 2 in the case of full amplitude, that is to say for example when sending a logical "1". The voltage at the circuit arrangement 3 remains unaffected by this. The supply-voltage control circuit 4 consequently carries out a decoupling of the load circuit LK, defined by the supply-voltage control circuit 4 and the circuit arrangement 3, and of the supply circuit VK, defined by the coil 1 and the rectifier circuit 2 as well as the supply-voltage control circuit 4. The current I through the supply circuit VK is in this case a measure of the amplitude modulation. The supply-voltage control circuit 4 has a charging capacitor 5 connected in parallel with it, serving as an energy store for the circuit arrangement 3. All the previously mentioned circuit parts can be realized as an integrated circuit on a semiconductor chip. It is possible in this case to lead the connecting points of the charging capacitor 5 to the outside with the supply lines 6, 7, so that an external capacitor can be connected to the semiconductor chip for increasing the charging capacity. As a second measure according to the invention, the current I is detected by a current measuring device SME, acting as an amplitude demodulator, the detected signal is demodulated and the data signal obtained in this way is delivered to the circuit arrangement 3. As a first possibility for a current measuring device, Fig. 2 shows a measuring resistor RM, which is arranged in the current path of the supply circuit VK, and the terminals of which are connected to a demodulator circuit DS. The voltage drop across the measuring resistor RM is a measure of the current I through the supply circuit VK and consequently a measure of the modulation of the carrier signal. Although the measuring resistor RM is simple to realize, the voltage drop caused by it is disruptive, since it restricts the range of the data carrier. In another embodiment of the - 6 - invention, the current measuring device is realized by a current mirror SP. Fig. 3 shows this. The transistor Tl, connected as a diode, of the current mirror circuit SP is arranged in the current path of the supply circuit VK, while the transistor T2 delivers at its drain terminal to the demodulator circuit DS the current to be demodulated, which is proportional to the current in the supply circuit VK. Such a current mirror circuit SP has the advantage that the voltage drop across the transistor diode Tl is small and this transistor Tl is non-reactive, since it operates in saturation. A further reduction in the voltage drop in the supply circuit VK is achieved according to Figs. 4 and 5 by the application of a bias voltage to the gate of the current mirror transistor Tl arranged in the supply circuit VK. A bias-voltage generating circuit can be realized with a voltage divider formed from resistors Rl, R2. In an advantageous development, the bias-voltage generating circuit is supplemented by a capacitor C to form a filter, in order to suppress voltage fluctuations at the parallel run controller 4 on account of load fluctuations. According to Fig. 5, for further stabilization of the bias voltage, the bias-voltage generating circuit may also be formed with a further voltage control circuit VRS. This may have the same reference voltage Uref applied to it as the supply-voltage control circuit 4. The reference voltage Uref is derived from the controlled supply voltage. One possible embodiment of a demodulator circuit DS is presented in somewhat more detail in Fig. 5. The current from the current mirror transistor T2 is passed via a controllable resistor RD. The voltage drop across this resistor RD is fed to a filter circuit FS for filtering out the direct component and, thereafter, to a comparator circuit KS, which detects the logic levels. A demodulator control circuit RS controls the resistor RD in such a way that, when there are slow current fluctuations, as caused for example by the mechanical movement of the data carrier in the electromagnetic field of a writing/reading device, a constant voltage drop is obtained. The demodulator control circuit RS is in this case connected in parallel with the resistor RD, which may be formed by an MOS transistor operating in the resistance range. The rectifier circuit 2 is formed by diodes. In integrated semiconductor circuits, these diodes are usually formed by transistors T21,...T24 connected as diodes. To avoid a further voltage drop in the supply circuit VK, these transistor diodes may be supplemented to form current mirrors - 7 - and the mirror current fed to a demodulator circuit. In Fig. 6, the transistor diodes T23, T24 of the rectifier circuit 2 leading to the positive-supply voltage line 6 have been supplemented to form current mirrors SP1, SP2. For reversing the direction, connected downstream of the current mirrors SP1, SP2 there is in each case a further current mirror SP3, SP4. In the example presented, the current mirror circuits SP1, SP2 lying in the rectifier circuit 2 are formed by n-channel MOS transistors and the downstream current mirror circuits SP3, SP4 are formed by p-channel MOS transistors. In the case of the embodiment of the invention according to Fig. 7, the diodes D1...D4 of the rectifier 2 are used as resistors, and the voltage drop across them is fed to a demodulator circuit as information on the current intensity. The advantageous design of this embodiment shown in Fig. 7 also comprises a rectifier reference branch with further diodes Dll, D22, which are connected in parallel with the diodes Dl, D2 leading to the positive supply voltage line 6. However, their connecting point is connected to the demodulator circuit DS, so that the latter can evaluate the differential voltage. A further possibility for the detection of the current flowing in the supply circuit VK is shown in Fig. 8. Arranged there in the supply circuit VK is a control transistor TR, which is driven by a control and demodulator circuit RDS. The control and demodulator circuit RDS is directly connected to the output terminals of the rectifier circuit 2, so that the input voltage is kept constant by the series controller formed by the control transistor TR and the control and demodulator circuit RDS. This takes place by driving the control transistor TR in such a way that its volume resistance is changed according to the current in such a way that the voltage drop across the control transistor TR remains constant. The control signal for the control transistor TR is then a measure of the current in the supply circuit VK and can be correspondingly evaluated. Fig. 9 shows a possible circuit for this. The input voltage derived from a ]voltage divider comprising resistors R3, R4, which are connected to the output terminals of the rectifier circuit 2, is compared by means of a comparator V with a reference voltage Uref1 and the differential signal is fed via a first bandpass amplifier BPV1 to the gate of the control transistor TR. The output signal of the comparator V is also passed via a second bandpass amplifier BPV2, which provides at its output the signal corresponding to the modulation. In principle, it is also possible to dispense with the bandpass amplifiers BPV1,.BPV2 if the comparator V itself has a suitable filter characteristic and the input of - 8 - the circuit arrangement 3 to which the demodulated signal 1 is fed is non-reactive, so that the control of the control transistor TR is not influenced. To protect the integrated circuits in contactless operation, voltage limiting circuits may also be provided on the semiconductor chip. For instance, both an AC voltage limiting circuit may be arranged upstream of the rectifier and a DC voltage limiting circuit may be arranged downstream of the rectifier. The data carrier according to the invention has so far been presented as operating in a purely contactless manner. It is, however, readily possible also to design it as a combined data carrier or dual-interface data carrier, that is to say to provide in addition to the receiving and transmitting coil 1 also contact areas to allow with-contacts operation. In with-contacts operation, it may be necessary to switch off the parallel run controller 4, in order that an excessive shunt current does not flow if a higher voltage than the parallel run controller would like to set is delivered by the contacts. For the corresponding driving of the parallel run controller 4, a further circuit which detects whether the data carrier is operating in the contactless or with-contacts operation is then necessary. Such a circuit can then detect and evaluate for example the presence of a supply voltage at the contacts and/or at the rectifier circuit connected downstream of the coil and/or the presence of a high-frequency carrier signal at the coil and/or the presence of a clock signal at the contacts. 9 We Claim 1. Data medium, comprising: - atleast one coil (1) for contactlessly receiving amplitude-modulated signals, - a rectifier circuit (2) connected down-stream of the coil (1), and - a circuit arrangement (3) for processing and / or storing data, - characterized in that the circuit arrangement (3) has a paralley connected supply voltage regulating circuit (4), and - in that a current measuring device (SME; RM, DS; SP; DS; TR, DS; Dll, D22, DS; SP1, SP2, DS) acting as an amplitude demodulator is arranged between the coil (1) and the arrangement comprising the supply voltage regulating circuit (4) and the circuit arrangement (3) for processing and / or storing data. 2. Data medium as claimed in claim 1 wherein the current measuring device is formed using a resistor (RM). 3. Data medium as claimed in claim 1, wherein the current measuring device is formed using a current mirror circuit (SP) arranged in the current path between the rectifier circuit (2) and the supply voltage regulating circuit (4). 4. Data medium as claimed in claim 3, wherein the control connection of the diode transistor (Tl) in the current mirror circuit (SP) is connected to the output of a bias voltage generating circuit (Rl, R2; VRS). 10 5. Data medium as claimed in claim 4, wherein the bias voltage generating circuit is formed using a voltage divider (Rl, R2). 6. Data medium as claimed in claim 4 or 5, wherein the bias voltage generating circuit is in the form of low-pass filter (Rl, R2, C). 7. Data medium as claimed in claim 4, wherein the bias voltage generating circuit is formed using an additional voltage regulating circuit (VRS). 8. Data medium as claimed in claim 1, wherein the current measuring device is formed using atleast one current mirror circuit (SP1, SP2) whose diode transistor(s) (T23, T24) also act as diode transistor(s) of the rectifier circuit (2). 9. Data medium as claimed in claim 1, wherein the current measuring device is formed using at least additional diode pair (Dll, 022), which is connected in parallel with a diode pair (Dl, D2) routed to a respective supply line of the rectifier circuit (2), has the same polarity and whose connection connecting the diodes forms the output of the current measuring device. 10. Data medium as claimed in claim 1, wherein the current measuring device is formed using an input voltage regulating circuit (TR, RDS) which is arranged in the current path between the rectifier circuit (2) and the supply voltage regulating circuit (4) and is in the form of a series regulator, where the actuating signal, which is proportional to the current to be measured, for the regulating transistor (TR) of the series regulator (TR, RDS) is evaluated. 11 11.Data medium as claimed in claim 1 of the preceding claims, wherein the current measuring device is formed using a demodulator circuit (DS). 12.Data medium as claimed in claim 11, wherein the demodulator circuit (DS) is formed using a controllable resistor (RD) which maps the current into a voltage and a demodulator regulating circuit (RS) which drives the resistor (RD). Data medium, comprising: atteast one coil (1) for contacttessly receiving amplitude-modulated signals, a rectifier circuit (2) connected down-stream of the coil (1), a circuit arrangement (3) for processing and / or storing data, the circuit arrangement (3) has a paratley connected supply voltage regulating circuit (4), and in that a current measuring device (SME; RM, DS; SP, DS; TR, DS; Dll, D22, DS; SP1, SP2, D5) acting as an amplitude demodulator is arranged between the coit (1) and the arrangement comprising the supply voltage regulating circuit (4) and the circuit arrangement (3) for processing and / or storing data.

Documents:

in-pct-2000-00279-kol-abstract.pdf

in-pct-2000-00279-kol-claims.pdf

in-pct-2000-00279-kol-correspondence.pdf

in-pct-2000-00279-kol-description(complete).pdf

in-pct-2000-00279-kol-drawings.pdf

in-pct-2000-00279-kol-form-1.pdf

in-pct-2000-00279-kol-form-18.pdf

in-pct-2000-00279-kol-form-2.pdf

in-pct-2000-00279-kol-form-3.pdf

in-pct-2000-00279-kol-form-5.pdf

in-pct-2000-00279-kol-letters patent.pdf

in-pct-2000-00279-kol-p.a.pdf

in-pct-2000-00279-kol-priority document others.pdf

in-pct-2000-00279-kol-priority document.pdf