Non-contact data carrier system

Details Non-contact data carrier system Non-contact data carrier system

1998-04-27

2002-12-03

Horabik, Michael (Department: 2635)

Communications: electrical

Selective

Intelligence comparison for controlling

C340S010340, C340S870030, C370S902000

Reexamination Certificate

active

06489883

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a non-contact data carrier system, for communicating by use of a radio wave, for uses for verification of various IDs, financial trading and control of a door lock of a car, and a non-contact data carrier used for the same.
A non-contact IC card as an example of the non-contact data carrier has a convenience that it is unnecessary to insert the non-contact IC card into a slot of a reader/writer as well as features of normal IC cards having a large storage capacity and a high-degree security function. Therefore, the non-contact IC card is a product of which a great market can be expected not only as a commuter ticket of public transportation and a ticket for a ski lift but also as a room entry/exit card for opening or closing a door and a card for electronic money. Such a non-contact IC card performs information transmission and reception with a question unit by use of a medium such as a radio wave. Power necessary for operation of a control circuit and a memory of the non-contact IC card is obtained from a battery incorporated in the card or by rectifying, by a radio wave transmitted from the question unit, an induced current generated due to mutual induction of a coil provided in the non-contact IC card.
FIG. 7
is a block diagram showing the configuration of a conventional non-contact IC card which operates on power supplied from a battery
29
. A main circuit unit
13
of the non-contact IC card comprises a reset circuit
5
, a demodulation circuit
6
, a modulation circuit
7
and a memory
12
. The main circuit unit
13
further comprises a control circuit
11
for controlling the above-mentioned circuits and performing reading from and writing to the memory
12
in accordance with the contents of a signal transmitted from a question unit (not shown). A transmitter-receiver
1
comprising an antenna and a tuning circuit (both are not shown) receives a radio signal transmitted from the question unit. A carrier signal detection circuit
3
compares the level of the received signal and a reference level preset in the carrier signal detection circuit
3
. When the level of the received signal is higher than the reference level, a switching circuit
8
goes into on state, so that power is supplied from a battery
29
to the main circuit unit
13
. As a result, the non-contact IC card operates. When the level of the received signal is not higher than the reference level, the non-contact IC card does not operate and goes into sleep state which is the state only to receive and detect a signal which will be again transmitted from the question unit.
In the non-contact IC card having the switching circuit
8
, power is supplied to the circuit components only when a carrier signal from the question unit is detected. Therefore, when no carrier signal is transmitted from the question unit, that is, when information transmission and reception is not performed between the non-contact IC card and the question unit, only the carrier signal detection circuit
3
consumes power, so that power consumption is reduced.
The above-mentioned non-contact IC card uses an internal battery
29
as the power source and the power necessary for operation of the non-contact IC card is supplied from the battery
29
. On the other hand, in a non-contact IC card which uses induced electromotive force generated at a coil incorporated in the non-contact IC card, rectified induced-electromotive-force is stored and the stored force is used for operation of the non-contact IC card. Therefore, the induced electromotive force generated in the coil decreases corresponding to increase of the distance between the non-contact IC card and the question unit. In order to prevent the induced electromotive force from decreasing, it is necessary to use the non-contact IC card in the proximity of the question unit at the time of communication.
That is, in the latter non-contact IC card, the longer the distance between the question unit and the non-contact card is, the lower the value of the induced electromotive force is, so that it is difficult to ensure the power necessary for operation. On the contrary, in the former non-contact IC card, since stable power is supplied from the battery
29
, long-distance communication can be performed.
Generally, the convenience of the non-contact IC card is influenced by a communication-possible distance between the question unit and the non-contact IC card. By increasing the communication distance between the non-contact IC card and the question unit, the non-contact IC card can be used at a position remote from the question unit, and thus the convenience is improved. The non-contact IC card in which power is supplied from a battery is excellent in convenience because a long communication distance can be ensured compared with the non-contact IC card using the induced electromotive force.
However, since the battery is required for operation, the non-contact IC card becomes inoperable when the capacity of the battery is low, that is, when the battery is exhausted. As described above, when the non-contact IC card is in sleep state, only the carrier signal detection circuit
3
is actuated for detecting a signal from the question unit. Therefore the power consumption is reduced. However, slight power is still consumed. Consequently, the battery is exhausted when the non-contact IC card is used for a long time. Normally, the non-contact IC card does not have means for displaying the remaining capacity of the internal battery, so that it is impossible for the user of the non-contact IC card to predict battery exhaustion. For this reason, the non-contact IC card is hardly used for important work or for recording important data.
When the battery is exhausted, the use of the non-contact IC card cannot be continued unless a replacement battery is at hand. Even if a battery is available, a tool such as a screwdriver is necessary for battery replacement, so that it is very difficult to replace the battery in a short time to use again the non-contact IC card.
An object of the present invention is to prevent a trouble caused by battery exhaustion of the non-contact IC card while maintaining the convenience that long-distance communication can be performed.
Another example of use of a conventional non-contact data carrier will be described hereinafter.
Conventionally, a door lock of a car employs a system for locking or unlocking the door by inserting a key into a key cylinder provided at the door and turning the key either leftward or rightward. In recent years, in order to simplify such locking or unlocking by use of a key, a wireless door lock system, namely, so-called keyless entry system has become widespread for locking and unlocking not only a door but also a trunk lid without the use of the key. In the keyless entry system, a locking or unlocking instruction is transmitted to a locking device for the door or the trunk lid from a position remote from it. The locking or unlocking instruction is given by use of light or a radio wave. For example, by pressing a push button
31
provided on a key terminal
30
as shown in
FIG. 8
, a key ID number is transmitted to the locking device of a vehicle. The key ID number is verified by a terminal device mounted in the vehicle. As a result of the verification, when the key ID number coincides with the key ID number of the vehicle, door locking or unlocking is performed. According to this configuration, even at nighttime or in an indoor parking lot where the keyhole of the key cylinder is not easily found because it is dark, door locking or unlocking can be easily performed without the key being inserted into the key cylinder. Recently, many vehicles have employed this system for the purpose of increasing their added values.
In this keyless entry system, it is necessary to take out the key terminal
30
and transmit the key ID number by pressing the push button
31
toward the vehicle every time door locking or unlocking is performed. Although it is unnecessary to look for the keyhole in order to

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