Contactless inductive data-transmission system

• US 5,345,231 A
• Filed: 08/23/1991
• Issued: 09/06/1994
• Est. Priority Date: 08/23/1990
• Status: Expired due to Term

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: MIKRON Gesellschaft für integrierte Mikroelektronik mbH
• Inventors: Koo, Roland, Holweg, Gerald
• Primary Examiner(s): Peng, John K.
• Assistant Examiner(s): Hill, Andrew
• Application Number:
  US07/748,942
• Time in Patent Office: 1,110 Days
• Field of Search: 340/870.31, 340/825.54, 340/825.57, 340/825.62, 340/825.63, 340/825.64, 340/870.32, 340/870.34, 340/870.19, 340/825.3, 375/21, 375/22, 375/25, 332/106, 332/108, 332/109, 332/112, 455/41
• US Class Current: 340/870.31
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: G07B 15/063 using wireless information transmission between the vehicle and a fixed station identification of vehicles G08G

Abstract

A contactless inductive data transmission system provides bidirectional signal transfer between a sending-and-receiving station and one or more batteryless transponders. A high-frequency signal from the sending-and-receiving station is pulse width modulated for data transmission to a transponder and provides a system clock, which is extracted in both the sending-and-receiving station and in the transponder for synchronization, and provides the electrical power for operation of the transponder. The pulse width modulated signal is demodulated in the transponder for triggering a response wherein a modulating signal is applied by load modulation to the pulse width modulated high-frequency signal to form an information-carrying load modulated high-frequency signal, which is demodulated in the sending-and-receiving station.

Claims

1. A contactless inductive data-transmission system, comprising:

at least one sending-and-receiving station including;

means for generating a given high-frequency signal which defines a clock rate,

modulating means connected to said means for generating for imparting information-carrying pulse width modulation with short even blanking intervals to said given high-frequency signal, thereby forming a pulse width modulated high-frequency signal,

a source of clock signals for extracting a system clock from said given high-frequency signal,

an inductor receiving said pulse width modulated high-frequency signal for inductively transmitting same and for receiving an information-carrying load-modulated high-frequency signal which is modulated by a modulating signal derived from said pulse width modulated high-frequency signal, said load modulation characterizing one logical value of a set of binary values "0" and "1" by a load modulation of the pulse width modulated high-frequency signal and the other logical value of said set being characterized by leaving the pulse width modulated high frequency signal unchanged, and

a demodulator connected to said inductor for demodulating said load-modulated high-frequency signal and deriving received information therefrom; and

at least one transponder energized by electrical power only inductively transmitted from said sending-and-receiving station in the form of said pulse width modulated high-frequency signal and including;

an inductive antenna coupled for wireless inductive signal transfer with said inductor upon said transponder being within a communication range of said station, a rectifier connected to said inductive antenna for recovering from said pulse width modulated high-frequency signal received by said inductive antenna from said inductor of said station, an energy signal electrically energizing said transponder, a clock extractor connected to said inductive antenna for recovering from said pulse width modulated high-frequency signal received by said inductive antenna from said inductor of said sending-and-receiving station, a system clock at said transponder synchronizing same with said sending-and-receiving station, a data storage connected to said inductive antenna for recovering data from said pulse width modulated high-frequency signal received by said inductive antenna from said inductor of said sending-and-receiving station, and for storing the recovered data represented by pulse width modulation, and

means connected with said inductive antenna for load modulation of the pulse width modulated high-frequency signal by the modulating signal derived from the pulse width modulated high-frequency signal received by the inductive antenna for producing the information-carrying load-modulated high-frequency signal transmitted to said inductor.

2. The contactless inductive data-transmission system defined in claim 1 wherein said inductive antenna of said transponder, for frequency independence of signals received thereby, is formed exclusively by at least one coil.

3. The contactless inductive data-transmission system defined in claim 2 wherein said inductive antenna of said transponder has two coils in an integrated configuration of said transponder and are formed of concentric turns in at least one plane on a single chip above an active semiconductor topography.

4. The contactless inductive data-transmission system defined in claim 3 wherein said coils are formed by photolithographic transfer on said chip.

5. The contactless inductive data-transmission system defined in claim 1 wherein said transponder includes a frequency divider, and said modulating signal derived from said pulse width modulated high-frequency signal has a carrier frequency derived from said frequency divider from the pulse width modulated high-frequency signal received by said inductive antenna.

6. The contactless inductive data-transmission system defined in claim 1 wherein said modulating signal is applied in said transponder to a switching device including a modulation transistor for loading and unloading at least partially inductively at least a portion of a coil forming said inductive antenna.

7. The contactless inductive data-transmission system defined in claim 1 wherein said transponder includes a current supply maintenance capacitor for bridging blanking gaps in said pulse width modulated high-frequency signal received by said inductive antenna.

8. The contactless inductive data-transmission system defined in claim 1 wherein said transponder includes a demodulator for demodulating said pulse width modulated high-frequency signal received by said inductive antenna and including a pause detector and a circuit responsive to duration of a signal following a pause and comparing said duration with a threshold for differentiating between "0" and "1" signals forming the data stored in said data storage.

9. The contactless inductive data-transmission system defined in claim 1 wherein said means for generating of said sending-and-receiving station includes an oscillator for generating said given high frequency signal and said inductor is an antenna connected to said oscillator, said modulating means of said sending-and-receiving station including a modulator connected to a data processor for pulse width modulation of the signal produced by said oscillator.

10. The contactless inductive data-transmission system defined in claim 1 wherein said demodulator of said sending-and-receiving station has a first demodulation stage and a filter for demodulating the load-modulated high-frequency signal and obtaining a modulation frequency, and a second demodulating stage for producing a bit stream upon the demodulation of the load-modulated high-frequency signal.

11. The contactless inductive data-transmission system defined in claim 10 wherein said modulating means and said demodulator of said sending-and-receiving station are connected to an interface and by said interface are connectable to a data processor.

12. The contactless inductive data-transmission system defined in claim 9 wherein said modulating means and said demodulator of said sending-and-receiving station are connected to an interface and by said interface are connectable to a data processor.