Data carrier

Details Data carrier Data carrier

1993-11-26

1996-05-28

Yusko, Donald J.

Communications: electrical

Continuously variable indicating

With meter reading

H04Q 700

Patent

active

055215904

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to data carriers such as industrial data tags, noncontact IC cards, livestock ID tags, electronic tickets, and electronic tags having no power source and carrying out noncontact data communication with fixed facilities. The distance between the data carriers and the facilities is more than several centimeters.
The present invention relates particularly to an improvement of an electromagnetic coupled data carrier having no battery and being operated by electric power induced in a coil by an alternating-current (AC) magnetic field emitted from the fixed facilities. The data carrier carries out bidirectional data communication with the fixed facilities, and can write and read data to and from an electrically erasable programmable nonvolatile memory incorporated in the data carrier.


BACKGROUND ART

There are various kinds of data carriers, and there are many methods to carry out bidirectional noncontact data communication between a data carrier and a fixed data control unit that is separated from the data carrier by a given distance.
Japanese Examined Patent Publication Nos. 3-12353 and 63-25393, Japanese Unexamined Patent Publication Nos. 51-15947 and 57-32144, U.S. Pat. No. 3,964,024, etc., disclose methods for carrying out bidirectional noncontact data communication between a portable data carrier such as a card and fixed facilities.
Most of these data carriers incorporate batteries. The distance between the data carrier and the fixed facilities having a control unit for carrying out the bidirectional noncontact data communication is usually fixed. Accordingly, errors rarely occur in data write and read operations.
As communication systems employing the data carriers become widely used, a need rises to reliably transfer data even if the distance between the data carriers and the fixed facilities varies widely. When the distance varies, the voltage of a transmitted signal detected at the data carriers and fixed facilities fluctuates. Accordingly, it will be impossible to bidirectionally transmit data with no errors or malfunctions.
The conventional data carriers having no batteries are incapable of writing and reading data or transmitting data to and from fixed facilities when a distance between them varies in a range of several centimeters to several meters. In particular, the presently marketed electromagnetic coupled data carriers having no batteries are only capable of reading data that are permanently or semi-permanently recorded. Various experiments have been made to freely rewrite data in a data carrier during use. Since an EEPROM used as a data storage unit needs a large rewrite voltage and since the EEPROM has insufficient reliability as a memory, no practical data carrier that is freely erasable and programmable has been proposed.
To solve the problems of the EEPROM, experiments have been made to use an SRAM as a data storage unit of the data carriers. Several data carriers employing SRAMs have been produced. This type of data carrier, however, must incorporate a battery. The battery has a limited service life and insufficient reliability. In addition, the battery increases the weight and size of the data carrier.
Among the prior arts, the Japanese Examined Patent Publication No. 3-12353 discloses a data carrier that is capable of writing and reading data, provided that a distance between the data carrier and fixed facilities is less than several centimeters. Due to this short distance, electric power can be easily supplied from the fixed facilities to the data carrier. Generally, this type of product is distinguished from the data carrier and is called a noncontact memory card.
The electromagnetic coupled data carrier having no power source frequently suffers a loss of voltage due to insufficient power from the fixed facilities. This results in incorrect logic operations of circuits in the data carrier, and it erroneously rewrites the electrically erasable programmable nonvolatile memory incorporated in the data carrier. To prevent such an accident,

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J. G. Nolan, "A Radiation Powered Single Chip EEPROM ID Code Transceiver", Proceedings of the IEEE 1987 Custom Integrated Circuits Conference, 4 May 1987, Portland, Oregon, pp. 684-686.
Eiichi Suzuki, "A Low-Voltage Alterable EEPROM with Metal-Oxide-Nitride-Oxide-Semiconductor (Monos) Structures", IEEE Transactions on Electron Devices, vol. ED-30, No. 2, Feb. 1983, pp. 122-128.
Semiconductor World 1989.7, pp. 98-100.
Semiconductor World 1991.4, pp. 112-115.
Semiconductor World 1969.7, pp. 102-106.

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