contactless coupling between a host unit and a smart card

• US 6,202,932 B1
• Filed: 10/01/1999
• Issued: 03/20/2001
• Est. Priority Date: 04/02/1997
• Status: Expired due to Fees

• Current Assignee: Juha Rapeli
• Original Assignee: Juha Rapeli
• Inventors: Rapeli, Juha
• Primary Examiner(s): Hajec, Donald
• Assistant Examiner(s): Taylor, Larry D
• Application Number:
  US09/409,912
• Time in Patent Office: 536 Days
• Field of Search: 235/380, 235/487, 235/491, 235/454, 340/825.72, 369/13, 369/18, 369/44.37, 369/116, 369/120
• US Class Current: 235/491
• 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 7/1097 Optical sensing of electronic memory record carriers, such as interrogation of RFIDs with an additional optical interface

Abstract

A method and module for transferring energy, clock frequency and data information without using an electrically conducting connection between a portable module and host equipment. Energy is transferred as optical radiation from at least two distinct light sources with intensities alternating between the minimum and maximum values in such a way that when one intensity goes from minimum to maximum the other goes from maximum to minimum wherein total intensity of optical radiation received by the module and supply voltage formed therefrom is nearly constant. The clock frequency is formed by and detected as the cyclical alteration of light intensities. Data is transferred as a modulation of the clock frequency.

Claims

1. A method of transferring energy, clock frequency and data from a host equipment to a smart card'"'"'s semiconductor chip which is connected to the host equipment without an electrically conducting contact, comprising the steps of:

transferring energy to the smart card as optical radiation from at least two distinct light sources;

varying light intensity of each of the light sources periodically between maximum and minimum values in such a way that while a radiation intensity of one of the light sources goes from minimum to maximum, a radiation intensity of the other of the light sources changes accordingly from maximum to minimum so that total intensity of light emission remains essentially constant;

transmitting the clock frequency via a cyclical alteration of energy transfer from the light sources wherein the alteration frequency of the radiation sources becomes the clock frequency for the smart card; and

transferring data as a modulation of the clock frequency.

2. The method according to claim 1, wherein the data information is demodulated using a pre-defined edge of one radiation intensity to trigger the state of the other radiation intensity to the logical state of the data.

3. The method according to claim 1, wherein the data transfer from the smart card to the host equipment is performed from the surface of the integrated circuit chip in the smart card by using an electromagnetic proximity connection.

4. The method according to claim 1, wherein the optical radiation from the distinct light sources are guided to separated areas on the smart card'"'"'s surface.

5. The method according to claim 1, wherein the optical radiation from the distinct radiation sources are guided to an essentially single area on the smart card'"'"'s surface and distinguished therein from their different wavelengths and using distinct detectors to detect different wavelengths.

6. A smart card for storing and processing of information, comprising:

a semiconductor chip in the card;

at least one optically transparent area on a surface of the card for receiving radiation from two or more light sources and for guiding the radiation on to a defined area on the semiconductor chip;

means for converting optical radiation guided to the defined area into electric energy, said means comprising,

two photo-voltaic converters, the first of said converters converting alternating radiation intensity into an electrical signal, and the second of said converters converting received alternating radiation intensity into an electrical signal, the radiation intensities being arranged in such a way that the sum of said electrical signals is essentially constant.

7. The smart card as in claim 6, further comprising means for producing a continuous operating voltage from the received alternating radiation intensities.

8. The smart card as in claim 6, wherein both photo-voltaic converters are connected to a triggering circuitry which converts the output of photo-voltaic converters into a two stage signal and that the output of the triggering circuitry is used as the clock signal of the smart card.

9. The smart card as in claim 8, wherein the triggering circuitry additionally contains a flip-flop circuit where a data input is connected to the output of one of said photo-voltaic converters, and a clock input is connected to the output of the other of said photo-voltaic converters, and the output of which is a data signal representing a value of one radiation intensity as triggered by an edge of the other radiation intensity.

10. The smart card as in claim 6, further comprising capacitive electrodes located on defined areas of the semiconductor chip, a potential of the capacitive electrodes being altered between two values according to data to be transferred from the smart card to a host unit.

11. The smart card as in claim 6, further comprising a pn-junction on a surface of the semiconductor chip, said pn-junction being optically observable through the surface of the smart card, and an optical reflection coefficient of said pn-junction being altered by a voltage across the pn-junction according to data to be transferred.

12. The smart card as in claim 6, further comprising an internal oscillator attached to a divider with a division number M, and another divider for dividing an externally applied clock frequency with a division number N for detecting via comparison whether the externally applied clock frequency is between a minimum and maximum values and thus acceptable for operation of the smart card.

13. The smart card as in claim 12, further comprising means for storing energy which is required during one basic operation in such a way that when the energy supply from an external source becomes interrupted during the operation, the smart card performs a controlled interruption by using said stored energy and the internal oscillator as the clock frequency.

14. A reader for a smart card having space for adopting and supporting the smart card, the reader comprising two light sources optically isolated from each other when the smart card is supported by the reader, a light intensity of each of said two light sources varying periodically between maximum and minimum values in such a way that while the light intensity of one of said sources goes from minimum to maximum, the light intensity of the other of said sources changes accordingly from maximum to minimum so that a total intensity of the light sources remains essentially constant.