JPH04112288A - Reflection ic card - Google Patents

Abstract

PURPOSE:To make a card itself durable by using a solar battery as the driving power source of a transmitting circuit which changes the impedance of an antenna in order to transmit data. CONSTITUTION:An antenna element 2 which refects the radio waves of continuous waves made incident by the change of the impedance, is installed, and the impedance of this antenna element 2 is changed by the on/off operation of an FET 3. On the other hand, the prescribed data to be transmitted are stored in a memory 4. Then, a solar battery 10 is used as the driving power source of each circuit except for the memory 4, that is, the transmitting circuit which changes the impedance of the antenna 2 in order to transmit the data. Thus, the card itself is made durable.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a reflective IC card, and particularly to a reflective IC card that is a so-called non-contact IC card using microwaves.

<Summary of the Invention> The present invention focuses on the feature of a reflective IC card that it can operate with low power because it is a reflective type, and actively utilizes this feature to provide an antenna for transmitting data. To provide a reflective IC card that uses a solar cell as a driving power source for a transmitting circuit that changes the impedance of the IC card, thereby making it possible to extend the life of the card itself.

<Prior Art> IC cards, which are formed by incorporating an IC (integrated circuit) inside a card-like structure, are used for various purposes. For example, in a logistics management system, an IC card is formed into a tag and used to identify goods, or in a security system, an IC card is formed into a card and used as a TD (personal identification tag) to be used at a gate. It is used to check people entering and exiting the airport.

Conventionally, a so-called contact type IC card has been generally used as this IC card. In contrast to this contact type IC card, a reflective type IC card, which is a non-contact type IC card using microwaves, has recently been developed by the applicant of the present invention and is being put into practical use. The transmission principle of this reflective IC card is, for example, an antenna that reflects incident microwaves of 2.45 GHz, a transmission data generation circuit, and an impedance that changes the impedance of the antenna in response to the transmission data. Data is transmitted using a reflective transmitter equipped with a change circuit, and the reflection characteristics of the antenna change in accordance with the change in impedance C of the antenna (Japanese Patent Laid-Open No. 1-18
(See Publication No. 2782).

According to this reflective IC card, the thickness of the card itself can be reduced to about 1 to 2 mm, which is at least about 3 to 5 mm for normal contact type IC cards.
Furthermore, it is possible to provide an IC cart with high reliability that operates with extremely low power.

<Problem to be solved by the invention> By the way, reflective IC cards are composed of a one-chip IC in which an oscillator, memory, drive circuit, etc. are integrated, and a lithium battery, for example, is used as the driving power source. For example, S (static) RAM can be used as a memory by constantly supplying power to the entire circuit.
When used, it also serves as the hank asop.

However, with reflective IC cards, the transmitting circuit for data transmission only needs to operate when transmitting data, but as mentioned above, the entire transmitting circuit operates at all times, and moreover, Since the power consumed by the drive circuit that drives the circuit occupies a large portion of the entire IC card, it is a waste of power, and as a result, the life of the battery is relatively short. In the drive circuit described above, the gate of the FET constituting the circuit has a small capacitance, and most of the power is consumed by switching the capacitance.

The power consumption of the entire IC card is about 2 CμA], and if a 5° [mA/l+] lithium battery is used for this IC card, the battery life is about 2 years.

In this way, the short lifespan of the built-in battery means that the lifespan of the IC card itself is short, and if you discard the IC card every time the built-in battery reaches the end of its lifespan.
Not only is it a waste of resources, but disposal of lithium batteries also increases environmental pollution, which is not desirable.

Furthermore, if an IC card is used as an ID card such as an employee ID card that does not require information to be changed over a relatively long period of time, reissuing IC cards for all employees every two years, for example, would require a huge amount of expense. Therefore, an IC card with a longer lifespan will be required.

Therefore, an object of the present invention is to provide a reflective IC card that allows the card itself to have a longer lifespan.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides an antenna for reflecting incident continuous wave radio waves, a memory for storing predetermined data, and a memory for transmitting the predetermined data. The reflective IC card has a built-in transmitter circuit that changes the impedance of an antenna in accordance with the data, and uses a solar cell as a driving power source for the transmitter circuit.

Effect> In the reflective IC card according to the present invention, by using a solar cell as a driving power source of a transmitting circuit that changes the impedance of the antenna in order to transmit data,
Since the transmitter circuit, which consumes most of the power, can be powered by solar cells, the lifespan of the card itself can be extended.

In other words, the lifespan of the IC card can be extended by using a non-volatile memory as the memory, or by using a volatile memory as the memory and using a secondary battery as a backup 7a '61 so that it can be charged with the surplus power of the solar battery. It becomes semi-permanent.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, the IC card 1 according to the present invention is capable of absorbing incident continuous wave radio waves due to its impedance change, for example, 2
．． It is equipped with an antenna element 2 that reflects microwaves of 45 GHz.

The impedance of this antenna element 2 is FET3
It changes depending on the on/off operation of.

On the other hand, predetermined data to be transmitted is stored in the memory 4. As the memory 4, for example, an SRAM having a large memory capacity is used. The memory 4 outputs stored data as parallel data. This parallel data is sent to the clock oscillator 6 in the converter 5.
It is converted into serial data in synchronization with a clock signal ck of a predetermined frequency outputted from the CK, and becomes a drive signal for the drive circuit 7 that drives the FET 3 on/off. The drive circuit 7 has a circuit configuration using, for example, complementary-connected FETs. And memory 4, converter 5
, the clock oscillator 6 and the drive circuit 7 are integrated into the IC chip 8
It has an integrated configuration.

Of the circuits built into the IC chip 8, the SRAM used as the memory 4 is a volatile memory that is constantly powered by a battery and its stored contents will disappear if it is not powered up. Next battery 9 is installed.
It is being As this secondary battery 9, for example, a lithium ion battery is used. In a lithium-ion battery, lithium ions emitted from a special lithium compound (ionic bond) in the positive electrode store and release electrical energy by traveling back and forth between the negative electrode and the metal lithium, which is extremely easily oxidized, is made from a special lithium compound. By replacing it with lithium compounds,
In addition to greatly increasing safety, the cyclability has been significantly improved through the appropriate combination of negative electrode materials and electrolytes.Furthermore, due to its high energy rating of 5 degrees, it has the same energy as a dry battery even though it is a storage battery, and has a cumulative The energy is more than 1,000 times that amount. In addition, paper-based lithium batteries have already been realized.

On the other hand, the I
The solar cell 10 is provided because the C card 1 is of a reflective type and can be operated with a low power battery. The voltage of one solar cell 10 is 0.6 (V)
For example, four silicon solar cells connected in series are used as a driving power source with a total voltage of about 2.4 (V).

In addition, in order to effectively utilize the surplus power of the solar cell 10,
A diode 11, which is a unidirectional element, is connected between the power line L1 of the solar cell 10 and the power line L2 of the secondary battery 9.
is connected. This diode 11 is connected to the secondary battery 9
When the voltage of the solar cell 10 becomes lower than the voltage of the solar cell 10, the secondary battery is selectively charged by surplus power of the solar cell 10 by becoming conductive.

All of the above-mentioned components are built into the main body of the IC card 1. That is, the antenna element 2 is printed and wired on a card board (not shown) which is the main part of the IC card 1, and the IC chip 8 is bonded to the board.
Furthermore, a secondary battery 9 and a solar cell 10 are mounted, and the IC card 1 is finally constructed by bonding sheet materials to the upper and lower surfaces of the substrate using a heat-sensitive adhesive.

When the IC card 1 configured in this manner is used as an ID card in a security system, for example, the card is worn on the chest or presented at the time of check, and energy is supplied to the solar cell 10 inside the card on the card reader side. If you prepare a light source for this purpose, you can use it without any problems even in places where sufficient light energy cannot be replaced by ambient light or at night. In other words, since the circuit portion that uses the solar cell 10 as its operating power source only needs to operate when transmitting data, if a light source is provided on the card reader side, the solar cell will be powered by the light energy from the light source when checking the card. 10 can obtain electrical energy and drive the above circuit parts.

For example, for the solar cell 10, four 0.6 (V) silicon solar cells are connected in series to provide a total power of 2.41 cm], and a load of 1 [MΩ] is connected to generate a power of 15 [W]. When used under the condition of 40 (cm) directly below two fluorescent lights,
It has been confirmed in field tests that an operating current of 2.4 [μA] can be obtained. Therefore, since the current consumption of a reflective IC card is about 2 [μA], 0.6
A drive power source using four (V) silicon solar cells is sufficient.

In addition, during the day, the solar cell 10 can convert the light energy of the sun or ambient light into electrical energy, so there is surplus power for driving only the circuit part that only needs to operate when transmitting data. Since the surplus power is charged to the secondary battery 9 via the diode 11, the surplus power can be used effectively.

In this way, as the driving power source for the circuit section for data transmission, the solar cell 10 is used because the 11c card 1 is a reflective type and can be operated with a small battery, while the hack-up of only the memory is used. In the case of , the current consumption is 1
SRAM has an extremely small value less than [μA]
By using the secondary battery 9 as a hack-up power source for the card and charging the secondary battery 9 with surplus power from the solar battery 10, the lifespan of the secondary battery 9 becomes semi-permanent. The lifespan of will also be semi-permanent.

Here, the principle of data transmission in a system using the reflective IC card 1 will be explained based on FIG. 2.

When a microwave band continuous wave transmission wave radiated from the transmission antenna 13 of the communicator 12, which is a card reader, is received, a voltage is induced in the seven antenna elements 2, and a reception current flows. Therefore, the received radio waves, that is, the transmitted waves from the communicator 12, are re-radiated from the antenna element 2. The re-radiated radio wave, that is, the reflected wave from the antenna element 2, is received by the communication antenna 12 and demodulated by the receiving antenna 14.

On the other hand, in the antenna element 2, the impedance between the feeding ends 2a and 2b changes depending on whether the FET 3 is turned on or off. When FET2 is turned on, the power feeding end 2a,
For example, the impedance between 2b is 50 [Ω],
Antenna element 2 is matched with a 2.45 (GHz) transmission wave. Also, when FET2 turns off,
The impedance between the feeding ends 2a and 2b is, for example, several hundred Ω.
], and the matching of the antenna element 2 collapses. The reflection characteristics of the antenna element 2 are different when the matching is achieved and when the matching is not achieved, and this causes a difference in the phase and amplitude of the reflected waves.

That is, in the IC card 1, the transmission data output as parallel data from the memory 4 is converted into serial data by the converter 6, the drive circuit 7 is driven by the clock signal ck from the transmission data unit 5, and the FET 3 is turned on/off. By doing so, when the transmitted wave from the communicator 12 is received, it is phase (or amplitude) modulated and reflected to the communicator 12 side. The communicator 12 receives the combined wave of the reflected wave and the transmitted wave and demodulates the phase (or amplitude) of the combined wave, thereby receiving the transmitted data from the IC card 1.

Note that in the above embodiment, a secondary battery is used as a backup power source for the memory 4 and charged with surplus power from the solar cell 10, but a primary battery may be used as a hack-up power source, although the battery life will be reduced. Of course,
Further, by using a non-volatile memory suitable for medium capacity as the memory 4, a bank-up power supply is not required, and the life of the IC card 1 becomes semi-permanent.

In addition, in the above embodiment, the light source of the solar cell 10 is provided on the card reader side, but in this case, the sensor detects when a person approaches the card reader, and the light source is activated only at that time to provide illumination. If you do this, I
This means that the power consumed by the entire D-card system can be saved, and if the system is set to a mode that does not illuminate even when someone approaches at night, it also serves as a kind of protection against the use of a stolen ID card, for example.

<Effects of the Invention> As explained above, in the reflective IC card of the present invention, most of the Since the transmitter circuit, which consumes power, can be powered by solar cells, the lifespan of the card itself can be extended.

In particular, by using SRAM as memory and a secondary battery as a backup power source that can be charged with surplus power from solar cells, or by using non-volatile memory as memory, the lifespan of the IC card can be extended semi-permanently. can be taken as a thing.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 2 is a diagram illustrating the principle of data transmission in a system using a reflective IC card. 1...IC card 2...Antenna element 4
···memory. 9... Secondary battery

Claims (3)

[Claims] (1) An antenna that reflects incident continuous wave radio waves,
In a reflective IC card that includes a memory for storing predetermined data and a transmitting circuit that changes the impedance of the antenna in accordance with the data in order to transmit the predetermined data, as a driving power source for the transmitting circuit. A reflective IC card that uses solar cells. (2) The reflective IC card according to claim 1, wherein the memory is a nonvolatile memory. (3) A claim characterized in that the memory is a volatile memory, uses a secondary battery as a backup power source, and has a unidirectional element that selectively supplies power from the solar cell to the secondary battery. The reflective IC card described in Item 1.