Communications: electrical – Selective – Interrogation response
Reexamination Certificate
1999-06-09
2003-09-23
Zimmerman, B (Department: 2635)
Communications: electrical
Selective
Interrogation response
C455S161300, C455S195100, C340S010100
Reexamination Certificate
active
06624743
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a responder, integrated circuit chip, non-contact IC card and device with no self-contained power supply in a non-contact IC card communication system, and a method of automatically adjusting the device with no self-contained power supply. More particularly, the present invention relates to adjustment of a resonance frequency in a device which performs an operation such as communication in an electrically non-contact state with another device by utilizing an electromagnetic wave.
DESCRIPTION OF THE BACKGROUND ART
Conventionally, a contact type IC card has been used for externally inputting/outputting data through an electrode of an IC (Integrated Circuit) embedded in a card. However, such contact type IC card must be inserted to a reading/writing device for input/output of data and is difficult to handle. Then, a non-contact IC card came into existence which performs electric power supply and data exchange using an electromagnetic wave. Such non-contact IC card is used, for example, for a gate at a station and a gate for a ski lift.
FIG. 19
is a circuit block diagram showing a structure of a communication system using such non-contact IC card. Referring to
FIG. 19
, the system includes an interrogator
50
(which is mounted for example in a gate for a ski lift), and a non-contact IC card
60
. Interrogator
50
transmits a high-frequency carrier from an oscillating circuit (OSC)
52
via an antenna
55
under control of a controlling portion
51
. When non-contact IC card
60
comes close to interrogator
50
, the high-frequency carrier is received by an antenna (a coil)
61
of non-contact IC card
60
. A power supply voltage generating circuit
64
converts the received high-frequency carrier to a direct current power for supply for the other circuit portion. Thus, non-contact IC card
60
can operate when it comes close to interrogator
50
. It is noted that power supply voltage generating circuit
64
, a modulating/demodulating circuit
65
, controlling portion
66
and non-volatile memory
67
are included in an IC chip
68
so that a small size is achieved.
Information is transmitted from interrogator
50
to non-contact IC card
60
by modulation of the high-frequency carrier by modulating/demodulating circuit
53
under control of controlling portion
51
. Non-contact IC card
60
demodulates the modulated high-frequency carrier by modulating/demodulating circuit
65
. Controlling portion
66
receives the demodulated information for performing a necessary process such as rewriting of a content in non-volatile memory
67
and transmission of information.
Conversely, information is also transmitted from non-contact IC card
60
to interrogator
50
. Here, an oscillating circuit is not provided on the side of non-contact IC card
60
. Thus, the high-frequency carrier which has not been modulated is transmitted form the side of interrogator
50
, and an impedance of a resonance circuit
63
including antenna
61
and a condenser
62
is changed by modulating/demodulating circuit
65
on the side of non-contact IC card
60
. Interrogator
50
detects and demodulates the change in impedance as that of resonance circuit
56
on its own side including antenna
55
and condenser
54
. Controlling portion
51
receives the demodulated information for performing a necessary process.
When non-contact IC card
60
is moved away from interrogator
50
, the operation of card
60
stops because power is not supplied anymore. However, the stored information is retained even when power is removed as non-volatile memory
67
is used.
Thus, the communication system using non-contact IC card
60
is operated.
In the above described conventional technology, however, variation in authorized parts or the like makes the resonance frequency of resonance circuit
63
on the side of IC card
60
deviate from a design value, whereby IC card is not supplied with sufficient power. As a result, communication between IC card
60
and interrogator
50
is allowed only over a short distance, or in the extreme case, the operation thereof may not be allowed.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a device which receives power supply from and communicates with the other device in a non-contact state and which is provided with a structure capable of suitably adjusting a resonance frequency of a resonance circuit.
Briefly speaking, a responder in a non-contact IC card communication system according to the present invention detects an output level of a resonance circuit by sequentially switching the resonance frequency of the resonance circuit by a switch circuit, and sets a switching manner of the switch circuit such that a desired output level is attained. Therefore, even when the resonance frequency is deviated from a suitable value due to initial variation in characteristic values of an antenna or condenser of the resonance circuit, the resonance frequency can automatically be adjusted to the suitable value for communication.
Preferably, a switching manner storing portion is provided which stores a preferred switching manner of the switch circuit. In this case, once the switching manner is stored, the resonance frequency needs not be sequentially switched for adjustment. Thus, an operation at the preferred resonance frequency can be rapidly performed.
More preferably, a reference voltage generating circuit is provided which receives an output voltage of the resonance circuit for generating a prescribed reference voltage. A magnitude of the output voltage of the resonance circuit in each switching manner is measured in accordance with the reference voltage. Thus, the output voltage of the resonance circuit is readily and correctly measured, thereby enabling correct adjustment of the resonance frequency.
More preferably, an output value storing portion is provided which stores an output value (measurement value) from the resonance circuit in each switching manner corresponding to the switching manner and, based on the stored content, a suitable switching manner is determined. Thus, the suitable switching manner is more readily and correctly determined.
More preferably, the switching manner which corresponds to the greatest output value is determined as the suitable switching manner. Thus, the resonance frequency can be adjusted such that the efficiency of the resonance circuit attains to the highest level.
More preferably, the output value is obtained every time the switching manner is switched and, when the output value exceeds a prescribed threshold value, the switching manner at the time is set as the suitable switching manner. Thus, automatic adjustment of the resonance frequency is rapidly performed.
More preferably, the switch circuit includes a plurality of transistors. Thus, the switching manner can readily and electrically be controlled for storage.
More preferably, the responder receives operation power from the resonance circuit. Thus, efficient power supply is ensured.
More preferably, communication of information is performed by the resonance circuit. Thus, efficient communication state is ensured.
More preferably, the suitable switching manner is determined during manufacture of the responder. Thus, even when the resonance frequency deviates from the design value due to variation in authorized parts or the like, a responder having a resonance circuit at a desired resonance frequency is readily manufactured.
More preferably, the suitable switching manner is determined once in a prescribed period of time. Thus, even when the resonance frequency changes due to secular change or change in ambient temperature, it is automatically adjusted to be back at a desired resonance frequency.
Further, briefly speaking, an integrated circuit chip used in a device with no self-contained power supply of the present invention detects an output level of a resonance circuit by sequentially switching a resonance frequency of the resonance circuit by a switch circuit, and determines and stores a switching manner of the
Chimura Shigemi
Ikefuji Yoshihiro
Yoshioka Satoshi
Arent Fox Kintner & Plotkin & Kahn, PLLC
Rohm Co., LTD
Zimmerman B
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