Contactless, inductive data transmission system.

p0001The invention relates to a contactless, inductive data transmission system between at least one transmitting and receiving station and one or more transponders, wherein the transmitting and receiving station comprises devices for the wireless transmission of an energy signal to the transponder, the clock transmission of a in an oscillator generated system clock, and for data transmission, wherein the or the transponder include a direct Richer for the received power signal, a Taktableiter for transponder synchronization and a data memory and wherein the energy transfer a generated in the transmitting and receiving station RF signal is provided, which is pulse width modulated to transmit data to the transponder.

p0002The data transmission and data retrieval between a possibly stationary transmitting and receiving station and one or more also addressed transponders is a very frequently encountered in the various fields of application tasks. Examples are the automatic road toll collection by automatic debit contact as soon as a vehicle-mounted transponder passes a transmitting and receiving station a tollgate. Credentials can-only operation to be controlled and access control systems allow the determination of the circumference of a locking authorization and monitor the individual entrees in Read. A tool change systems on machine tools, the controller can be made due to the provided on each tool transponder, wherein the transponder data provide parameters on tool type, tool life including error correction information.

p0003In order to solve the above defined objects are known from WO-A-88/03684 transmitting and receiving stations, which supply the transponder on an inductive basis by transmitting a RF signal with energy. This energy is stored in one embodiment in a capacitor and used for activation of a microprocessor in the transponder returns data to the memory of the transmitting and receiving station. The digital technology requires a clock transmission and synchronization of the interacting station. In the known data transmission system of the clock is transmitted through regelwäßige interruptions of the energy signal. Further, the high frequency signal of a load modulation is subjected to a short circuit of the resonant circuit in the antenna field of the transponder, which is recognizable in the transmission and Emfpangsstation.

p0004Significant demand which is specific to the transponder, is to achieve a minimum size. The energy supply by means of a capacitor storage required transponder side relatively large capacitors. The incorporation of an oscillator for data returning to the transmitting and receiving station miniaturization is detrimental. Finally, the aforementioned load modulation requires using a resonant circuit an exact resonant frequency, compliance not only specific components and for example temperature compensating measures require, but also restricts the application due to different regulatory provisions territorial.

p0005The invention aims to provide a data transmission system of the aforementioned type with a compact design, which is a miniaturization by Single Chip accessible to design as flexible as possible to meet all applications requirements. This is achieved according to the invention, clock signal from the carrier frequency of the RF signal is derived, and that the RF signal is used for data transmission from the transponder to the transmitting and receiving station by a pulse code modulated signal load modulated. This one generated in the transmitting and receiving station signal can be optionally used for bidirectional information exchange for full duplex connection, since it simultaneously transports energy, clocks, pulse width modulated signals emitting and is load-modulated by the transponder in the opposite direction by a pulse code modulated signal. This technology allows the lowest possible dimensions specifically the transponder and provides a result of the pulse width modulation for the transponder data transmitted information and the pulse code modulation guided load in the opposite direction optimum reliability. It is advantageous if the or the transponder having an antenna circuit comprising the frequency independence of the received signal exclusively one or more coils. In contrast to the prior art, the antenna circuit does not include a resonant circuit. Thereby, it is not necessary to permanently maintain a rigid frequency. Thus beispeilsweise produced are a Chipfürweitweite application which received the required different frequencies, evaluate and optionally can load modulate the return of information. The coil or coils are arranged concentrically in an expedient method of payment in an integrated embodiment of the transponder and the transmitting and receiving station in particular as a single chip above the active semiconductor topography in one or several levels, preferably applied in a photolitographischem method. This embodiment of the two-dimensional footprint of the chip is not increased, and the coil or coils integrated into the chip. To transfer data from the memory of the transponder by means of load modulation for transmitting and Empfangssta tion, it is advantageous if the carrier frequency of the transponder side pulse code modulated signal is one of a frequency divider derived, obtained by dividing the received frequency of the energy carrier frequency. This reduces the circuit complexity while increasing the operational safety. As mentioned, transmission system according to the invention is not bound to a solid, necessary for the transponder circuit frequency and it will not be fed directly to the data of the memory of a switching device, but it is the performed by the storage content pulse code modulated signal in the transponder to a switching device, particularly a modulation transistor for switching on or off of an inductor or partial inductance, preferably the antenna coil and the resistive load turned thereof. During the blanking intervals of the coming of the transmitting and receiving station pulse width modulated signal is omitted in the transponder of the clock, so that will be returned in the gaps and load-modulated no information and therefore no loss of information. To ensure a continuous power supply, it is expedient if, for bridging the blanking information related occurring in the energy source power supply circuit of the transponder is a back-up capacitor Pre seeing. Due to the very short blanking intervals may be very small, the capacitor, so that no space problems in the topography of the chip occur. To recover the data transmitted from the transmitting and receiving station data of the antenna coil of the transponder is connected downstream of a demodulator for the pulse width modulated signal provided by a pause detector and a time or frequency counter for determining the signal length between the pauses as well as a comparison circuit with a threshold value to differentiate zero and one signals having. Conversely, a is switched to its antenna filter is provided with a demodulator of the amplitude modulation of the transponder side load modulated energy carrier in the transmitting and receiving station, wherein preferably a second demodulation section is connected to the presentation of the next transponder from the bitstream. In the sense of a variable extensive applicability modulator and demodulator of the transmitting and receiving station via an interface are connected to a data processing system.

p0006An embodiment of a data transmission system according to the invention is shown in the form of block diagrams and signals. FIG. 1 shows a block diagram of a transmitting and receiving station, Fig. 2 is a block diagram of a transponder, Fig. 3 is a pulse width modulated energy source, Fig. 4 a load modulated energy source, Fig. 5, obtained from Fig. 4 signal to the first and Fig. 6 after the second demodulation stage.

p0007According to FIG. 1, an RF signal for transmission of energy, clock and information to a transponder 3 (Fig. 2) is generated in a transmitting and receiving station 1 in an oscillator. The frequency of the RF signal results in the system clock (time base) in both the transmitting and receiving station and in the transponder 3. This thus synchronized system clock is obtained from the RF signal of the oscillator 2 in a Taktableiter 4th A control unit 5 serves as a higher-level control for the transmitting and receiving station 1. Further, the leads preferably to 100% amplitude modulated RF signal to the battery-less transponder 3 to energy. The information that flows through an interface 6 from a memory of a data processing system, is modulated via a modulator 7 to the RF signal of the oscillator 2 by pulse width modulation. This modulation causes blanking intervals, which expressed a greater or smaller number of RF oscillations or different, a longer or shorter RF signal follows. The signal length after each blanking interval or the number of vibrations are a criterion for a zero or one information to be transmitted in the digital data system. This pulse width modulated, Diplomatic leading energy and transporting RF signal is shown in Fig. 3. It is extracted in accordance with Figure 1 through an antenna coil 8 from the oscillator. 2

p0008The circuit of FIG. 1 further shows still a demodulator 9, the information about the antenna coil 8 receives for bidirectional optionally taking place in full-duplex flow of information and the interface 6 forwards to the data processing system. On these circuit 2 and 4 to 6 will be discussed subsequently in connection with FIGS..

p0009A transponder 3 includes an antenna coil 10 with a downstream rectifier 11 and a voltage regulator 12 and a reset generator 13, which locks the entire transponder circuit at the operating below a still reliably guaranteeing minimum voltage. Power is supplied with approximation of the or one of the transponders on the or a transmitting and receiving station 1 due to the transmitted RF signal. The transponder 3 detects the system clock in a Taktableiter 14 and demodulates the via the antenna coil einlangende pulse width modulated RF signal in a demodulator 15 comprises this a pause detector for detecting blanking intervals (Fig. 3) between the signal blocks and a counter of the length signal block notes by frequency pulse counting and compares with a threshold. Short signal blocks is the number of vibrations below the threshold, put a zero signal and long signal blocks whose vibration is number above the threshold, the one signal in the digital data system. Via a control unit 16 to transfer the data and enters the information into a memory 17. In the control unit 16 all the logical functions and processes of the transponder 3 are summarized. Depending on the application, different communication protocols, data validation, access control and other logic operations can be implemented. As data storage 17 may EEPROM cells, also be provided with back-up battery or wiring options RAM cells.

p0010The data transmission system between one or more transmitting and receiving statins 1 and preferably a greater number of transponders 3 is bidirectional with timeshifting information flow in both directions or in full duplex with simultaneous data transmission. For this purpose, the transponder 3 a via the control unit 16 and the memory 17 guided modulator 18 is provided which provides a pulse code modulated information-carrying signal by dividing the system clock of the Taktableiters 14, which is used for controlling a modulation transistor. This lies in a circuit of the antenna coil 10 and switches an additional inductance or a partial winding of the antenna coil 10 increases or decreases, depending on the digital signal sequence and the deduced above pulse code modulated divided RF frequency (system frequency). The change in the inductance produces a retroactive on the transmitting and receiving station 1, load modulation of the generated oscillator 2 in the RF signal. The corresponding signal is shown in Fig. 4. The RF energy source is amplitude-modulated in certain areas. This amplitude modulation is derived from the information-dependent change in load by the variable impedance of the antenna coil 10 which, as mentioned, achieved by connecting and disconnecting of coil turns. This has the advantage that the antenna for receiving energy for the transponder 3 is always available, the system can be operated independent of frequency within wide limits and no measures to comply with a rigid frequency are necessary. Thus, the transponder 3 can be manufactured as a mass product in each case identical without about an adjustment or adaptation for a predetermined receiving frequency would be necessary. The components are integrated monolithically, including derAntennenspule that can be placed in a layer on the semiconductor topography of the chip in a concentric winding arrangement.

p0011In the transmitting and receiving station 1, a demodulator 9 is provided with a filter, which detected via the antenna coil 8 load modulation (RF signal as shown in FIG. 4) to a signal sequence as shown in FIG. 5 regenerated. A second demodulation stage causes the recovery of the bit sequence of the digital signals. Coming from the transponder 3 solves information in the data processing system connected via the interface 6 and from appropriate commands or or functions. An information loop can be set up and maintained by control processes in this way to establish the identity of the transponder address and reconfirmation (shake hands) for controlling processes of organizational, accounting or technical nature as well.

p0012For the energy supply of the transponder 3 with high efficiency the blanking (blanking) is chosen so that it can detect one part of the demodulator 15 at the transponder 3 reliable, and that the consequent interruption can be bridged in the energy supply by the smallest possible backup capacitor. Bridging the gaps is also favored by the fact that no clock signal for the transponder 3 is present in the blanking and thus the power consumption is extremely low. If multiple transponders 3 are provided in the transmission and reception area of ​​a station 1, there is the problem of individual identification. This can be done by successive interrogation. Once the transmitting and receiving station 1 by the presence protocol has detected the presence of several transponders 3, the query whether a transponder is out of a half of the total number of transponders in the detection range of the transmitting and receiving station 1 starts. This is done by the transmitting and receiving station transmits an interrogation protocol. a transponder or more Located in the surveyed group in the vicinity of the transmitting and receiving station 1, so respond to this by transmitting their individual codes and some test bits to the transmitting and receiving station. Replies only one transponder, so this is now been identified. Several transponders respond, this results in a synchronous superposition of the responses, which is detected in connection with the check bits on the transmitting and receiving station first Now, the transmitting and receiving station sends another query, the surveyed group of transponders is reduced again by half. This continues until only one transponder responds. Replies so continues to a query towards no transponder with the subdivision of the complementary transponder group. If a transponder is identified, a further identification of the same transponder according to various criteria can be prevented. It can for example be defined a time window during which a transponder may be identified only once. Or it can be ensured that the same transponder can be identified only again after all the other transponders present in the detection range of the transmitting and receiving stations were identified.