JPH0471089A - Ic card - Google Patents

Abstract

PURPOSE:To prevent the mixing of radio waves for data transmission/reception with other radio waves by providing an IC card for transmitting/receiving data by means of radio waves with plural resonance circuits and a switching circuit for switching the resonator circuit and setting up the resonance frequency of the resonance circuits to the carrier of the radio waves. CONSTITUTION:The IC card is provided with a transmitting/receiving circuit 12a connected to the resonance circuits consisting of a coil 13 and capacitors 14a to 14d. A radio wave from a card reader/writer is inputted to a CPU 12e as a trigger signal through the resonance circuit RF consisting of the coil 13 and the capacitor 14d, the circuit 12a and an I/O circuit 12b to start a CPU 12e. Then, the CPU 12e receives the frequency code of the radio wave and one of the capacitors 14a to 14c is selected by the frequency code through a switch 15a to set up resonance frequency. Then, data are transmitted/received by the frequency. After completing communication, the resonance frequency is reset and a waiting state based on reference frequency is restored.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an IC card that transmits and receives data using radio waves.

[Conventional technology]

FIG. 4 is a block diagram of a conventional IC card of this type. The IC card 1 includes a battery 11 that supplies power to each part of the circuit,
A microcomputer chip 12, an oscillator 16 that outputs a clock CLK, a coil 13, and a capacitor 14
is built-in.

The microcomputer chip 12 includes a transmitting/receiving circuit 12a that amplifies input voltage, modulates and demodulates it, converts input parallel data from parallel to serial, outputs serial data, and converts input serial data to serial data. / input/output circuit 12b that performs parallel conversion and outputs parallel data, and RAM 12c that is data memory.
, a ROM 12d which is a program memory, a CPU 12e which processes data, and a lotus 1 which transmits data.
2f is built-in.

The positive and negative electrodes of the battery 11 are respectively connected to the positive and negative terminals 1e and Ig of the microcomputer chip 12, and the negative terminal 1e is connected to the ground line GND.

A coil 13 and a capacitor 14 are connected in parallel to form a resonant circuit RF, one end of which is connected to the input/output terminal 1d of the microcomputer chip, and the other end connected to the ground line GND.
is connected to. The clock CLK of the oscillator 16 is applied to the clock terminal 1h of the microcomputer chip 12. The input/output terminal 1d is connected to the input/output circuit 12b via the transmitting/receiving circuit 12a. Input/output circuit 12
b, RAM 12c, ROM 12d,,C
PU12e is connected to lotus 12f.

In this IC cart 1, when the CPU 12e supplies parallel data to be transmitted to the input/output circuit 12b via the path 12f, the input/output circuit 12b converts the parallel data into serial data and inputs the serial data to the transmitting/receiving circuit 12a. The transmitting/receiving circuit 12a modulates the serial data and applies it to the resonant circuit RF of the coil 13 and the capacitor 14 via the input/output terminal 1d, and transmits the modulated serial data to the resonant circuit 1? With F as an antenna,
Data is transmitted using radio waves with a unique resonant frequency as a carrier wave. On the other hand, a radio wave with transmitted data is received by a resonant circuit RF which is an antenna, a voltage induced in the resonant circuit RF is amplified by a transmitting/receiving circuit 12a, and the serial data is demodulated and inputted to an input/output circuit 12b. do. The input/output circuit 12b converts the input serial data into parallel data and provides the converted parallel data to the RAM 12c via the hash 12f, and the received data is written into the RAM 12C.

In this way, the IC card 1 transmits and receives radio waves using a unique resonant frequency as a carrier wave.

FIG. 5 is a block diagram of another IC card of this type.

This IC card 1 has a built-in microcomputer chip 12 provided with an output terminal 1a and an input terminal 1b connected to a transmitting/receiving circuit 12a.

One end of a resonant circuit RF in which a coil 13A and a capacitor 148 are connected in parallel is connected to the output terminal 1a, and the other end is connected to a ground line GND.

This resonant circuit RF serves as a transmitting antenna.

One end of a resonant circuit RF2 in which a coil 13B and a capacitor 14B are connected in parallel is connected to the input terminal 1b.
The other end is connected to the ground line GND.

This resonant circuit RF2 serves as a receiving antenna.

The resonance frequency of the coil 13A and the capacitor 14A is made different from the resonance frequency of the coil 13B and the capacitor 14B. The configuration other than these is the same as the IC card configuration shown in the fourth cabinet. Thereby, this IC card transmits and receives radio waves for transmitting data and radio waves for receiving data separately using different resonant circuits.

[Problem to be solved by the invention]

The above-mentioned IC card transmits and receives radio waves to and from, for example, a card reader/writer. By the way, the IC shown in Figure 4
Cards use the same frequency of radio waves to transmit data and receive data, so they can be used in environments where multiple card readers/writers exist, such as when an IC card is used for a commuter pass. In environments such as station ticket gates, multiple card readers/writers transmit strong radio waves of the same frequency, causing interference. That is, when an IC card is transmitting and receiving data to and from a specific card reader/writer, it is affected by radio waves transmitted by other card readers/writers. Another problem is that there is a risk of interference between card readers/writers.

On the other hand, the RC card shown in Figure 5 has different resonance frequencies when transmitting radio waves and when receiving radio waves, so radio waves can be transmitted between the IC card and a specific card reader/writer. When transmitting and receiving, it becomes difficult to be affected by radio waves emitted by other card readers/writers, but it is possible to create a resonant circuit with a coil and a capacitor as IMi.
Because of the circuitry required, it is extremely difficult to mount them in an IC cart with limited dimensions, resulting in an increase in the cost of the IC card.

The present invention has been developed in view of such problems, and in an environment where a plurality of card readers/writers are transmitting radio waves, even if radio waves are transmitted/received to/from a specific card reader/writer, it is not affected by the radio waves transmitted by other card readers/writers. To provide an IC card without increasing cost.

[Means to solve the problem]

The IC card according to the present invention includes a resonant circuit consisting of a combination of a single coil and a plurality of capacitors, or a combination of a plurality of coils and a single capacitor, and a switching means for selectively switching the coil or the capacitor. The configuration is such that the resonant frequency of the resonant circuit is used as the carrier wave of the radio wave.

[Operation] The resonant circuit is a combination of a single coil and a plurality of capacitors, or a combination of a plurality of coils and a single capacitor. When the capacitor or coil is selected by the switching means, the resonant frequency is determined.

Radio waves are transmitted and received using this resonant frequency as a carrier wave.

As a result, radio waves can be transmitted and received using the specified resonant frequency as a carrier wave, and interference with other radio waves can be avoided.

(Example〕 The present invention will be described in detail below with reference to drawings showing embodiments thereof.

FIG. 1 is a block diagram of an IC card according to the present invention.

The IC card 1 includes a built-in battery 11 that supplies power to various parts of the circuit, a microcomputer chip 12, an oscillator 16 that outputs a clock CLK, a coil 13, and capacitors 14a, 14b, and 14c of different capacities. ing. The microcomputer chip 12 includes a transmitting/receiving circuit 12a that amplifies, modulates, and demodulates the input voltage, and switches 15a, 15b, and 15c that operate to select the capacitors 14a, 14b, and 14c.
An input/output circuit 12b that converts input parallel data from parallel to serial and outputs serial data, and converts input serial data from serial to parallel to output parallel data, and RAM which is a data memory.
12C, a ROM 12cl which is a program memory, a CPU 12e which processes data, and a lotus 12f which transmits data.

The positive and negative electrodes + and - of the battery 11 are respectively connected to the positive and negative terminals 1e and Ig of the microcomputer chip 12, and the negative terminal 1e is connected to the ground line GND inside the microcomputer chip 12. There is. Further, a reference voltage electrode V, which outputs a reference voltage corresponding to, for example, 2 of the voltage between the positive and negative electrodes + and - of the battery 11, is connected to the reference voltage terminal 1f, and the reference voltage is transmitted to the transmitting/receiving circuit 12a. It is designed to be given to One end of the coil 13 is connected to the coil connection terminal 1d of the microcomputer chip 12, and one end of the capacitors 14a, 14b, and 14c are connected to the capacitor connection terminals 1a, lb, and lc, respectively. Coil I3 and capacitor 14a,
The other ends of the coil 13 and the capacitors 14a, 14b, 14c form a resonant circuit R.
F is formed. Furthermore, by applying the reference voltage of the reference voltage terminal 1f to the coil 13 and the capacitors 14a, 14b, and 14c, the voltage generated in the coil 13 when transmitting and receiving radio waves changes in the positive and negative directions around the reference voltage. It looks like this. The coil connecting terminal 1d is directly connected to the transmitting/receiving circuit 12a, and the capacitor connecting terminals 1a, lb, lc are connected to switches 15a, 15b,
15c are connected to the transmitting/receiving circuit 12a separately.

The clock CLK of the oscillator 16 is given to the clock terminal 1h of the microcomputer chip 12, and
2e, RAM 12c, ROM 12d, etc. The transmitting/receiving circuit 12a is connected to the input/output circuit 12b. Input/output circuit 12b, RA
M 12c, ROM 12d.

The CPU 12e is connected to the lotus 12f.

FIG. 2 is a circuit diagram of switches 15a, 15b, and 15c.

The coil connection terminal 1d is connected to the coil connection terminal 1d.
22a (corresponding to switch 15a) to capacitor connection terminal 1a, CMo5 transmission gate 22b (corresponding to switch 15b) to capacitor connection terminal 1b, and CMO3) transmission gate 22.
c (corresponding to the switch 15c), and is connected to the capacitor connection terminal 1c. Data bus 2 in lotus 12f
Data for a, 2b, and 2c are D Frinobufu o Tubu 21a
21b and 21c, respectively.

The outputs of the output terminals Q and Q of the D flip-flop 21a are as follows.
The outputs of the output terminals Q and Q of the D flip-flop 21b are separately applied to the gates of the N and P channel MOS transistors of the CMO5 transmission gate 22b. It is given. The output of the output terminals Q and Q of the D flip-flop 21c is the N of the CMO5) transmission gate 22c.
, P-channel MOS) are provided separately to the gates of the transistors. Address lotus 2e in lotus 12f
The data is given to the address decoder 23, and its output is given to each trigger terminal T of the D flip-flops 21a, 21b21c.

Next, the transmission/reception operation of the IC card configured in this way is described by CP.
This will be explained with reference to FIG. 3 showing the control contents of U 12e.

Now, when the IC card 1 receives a radio wave from, for example, a card reader/writer (not shown), a voltage is induced in the coil 13 of the resonant circuit RF. The voltage is input to the transmitter/receiver circuit 12a. The transmitting/receiving circuit 12a amplifies and demodulates the input voltage and inputs the result to the input/output circuit 12b.

Thereby, the input/output circuit 12b outputs the serial/parallel converted parallel data to the lotus 12f.

When the trigger signal from the card reader/writer is input to the CPU 12e in this manner, the CPII 12e is activated (Sl). Subsequently, a frequency code indicating a resonant frequency as a carrier wave of radio waves from the card reader/writer is received (S2). This frequency code is the address bus 2a, 2
It is input to the address decoder 23 via b and 2c.

Then, the address decoder 23 decodes the frequency code and sends the signal to the D free knob flop 21a.

21b, 21c, the D flip-flops 21a, 21b, 21c enter the cent state corresponding to the frequency code.

In other words, the D flip-flops 21a, 21b, 21
The resonance frequency is set using c (S3). For example, CMO
5) Lance mission gate 22a turns on and other commercials
When the O5 transmission gates 22b and 22c are turned off, the resonance frequency is determined by the coil 13 and the capacitor 14a. Then, the resonant circuit having the determined resonant frequency receives the radio wave from which the card reader/writer has transmitted data, and the transmitting/receiving circuit 12a amplifies the voltage induced in the coil 13 by the received radio wave. Also, the transmitter/receiver circuit 12
The CPU 12e sets the division ratio of the original oscillation frequency of the clock CLK to a value corresponding to the resonant frequency, demodulates the divided frequency by multiplying by 7, and receives the data transmitted by the card reader/writer. .

In addition, when transmitting data from the IC card 1 to the card reader/writer, the CPU 12e outputs the data to be transmitted to the lotus 12f, inputs it to the input/output circuit 12b, converts the parallel data from parallel to serial, and converts the data. Serial data is input to the transmitting/receiving circuit 12a. The transmitter/receiver circuit 12a modulates the signal using a clock divided according to the resonant frequency in the same way as when receiving, emits a radio wave using the resonant frequency of the coil 13 and the capacitor 14a as a carrier wave, and transmits the modulated signal to the card reader/writer. (S4). When data transmission and reception are completed through such an operation, the CMOS transmission gate 21a that was on is turned off, the resonance frequency setting is canceled (S5), and the IC
The card 1 is placed in a standby state for transmission and reception (S6), and the series of operations for transmitting and receiving data via radio waves is completed. Subsequent reception of the trigger signal from the card reader/writer and reception of the frequency code of the resonant frequency are performed using the fundamental frequency after the resonant frequency setting is canceled.

In this way, the IC card determines the resonant frequency to be used as a radio wave carrier wave based on the frequency code sent from the card reader/writer, and uses that resonant frequency to transfer data between the IC card and the card reader/writer using radio waves. It will be sent and received. Therefore, even in an environment where multiple reader/writers are transmitting radio waves, interference does not occur and the IC
Cart reliability can be greatly improved. Furthermore, since the resonant frequency can be changed as appropriate, transmitted data cannot be easily received, which has the effect of preventing data theft. Further, a barrier pull capacitor may be used instead of selectively switching a plurality of capacitors, but when capacitors are selectively switched, battery power consumption is reduced and the cost of the IC card can be reduced.

Furthermore, more different resonant frequencies can be obtained by changing the combinations of switches that are turned on.

In this embodiment, the card reader/writer determines the resonant frequency of the IC card, but the resonant frequency may be determined by the IC card. In that case, a coil or a capacitor is selected according to the determined resonance frequency, and radio waves are transmitted and received in the same manner as described above.

Furthermore, although radio waves are transmitted and received at the same resonant frequency, the resonant frequency may be different between transmission and reception.

Furthermore, when a resonant circuit is formed by a single coil and a plurality of capacitors, the resonant circuit can be made most compact.

〔Effect of the invention〕

As detailed above, the present invention provides a resonant circuit consisting of a combination of a single coil and a plurality of capacitors, or a combination of a plurality of coils and a single capacitor, and selects a capacitor or a coil. Since the resonant frequency can be changed as appropriate, when transmitting and receiving radio waves, the resonant frequency can be determined and the radio waves can be transmitted and received using the resonant frequency as a carrier wave. Therefore, according to the present invention, even if an IC card is used in an environment where a plurality of devices are emitting radio waves, there is no interference, and the IC card has high reliability of transmitted and received contents.
Can provide C card. In addition, since the resonant circuit provided in the IC card does not include the same number of coils and capacitors, the resonant circuit can be made smaller, resulting in excellent effects such as making the IC card smaller and reducing costs.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the IC card according to the present invention, Fig. 2 is a circuit diagram of its switch, Fig. 3 is a flowchart showing the control contents of the cPU, Fig. 4 is a block diagram of a conventional IC card, and Fig. 5 is a block diagram of the IC card according to the present invention. The figure is a block diagram of another conventional IC card. l... IC car)' 11... Pond 12... Microcomputer chip 12b... Input/output circuit
12e...CPL112f...Has 13...Coil 14a, 14b, 14c...Capacitor
15a, 15b, 15c...Switch 16...
- Transmitter In the figures, the same reference numerals indicate the same or equivalent parts. Agent: Masuo Oiwa Figure 2, name of the invention IC card 3, volunteer written by the representative of the person making the amendment) ” column, Drawing 6, Contents of Amendment 6-1 “Detailed Description of the Invention” column (1) On page 9, line 1 of the specification, the phrase “one end of the coil 13” has been changed to “
One end of the coil 13 and one end of the capacitor 14d are corrected. (2) r14a, 14b, 14 on page 9, line 4 of the specification
c j means r14a, 14b, 14c, 14d
Correct it as j. (3) On page 14, line 9 of the specification, the phrase ``If switched, the battery power consumption will be reduced.'' has been replaced with ``If the switch is switched, there is no need to generate analog voltage, so the battery power consumption will be reduced.'' I am corrected. 6-2 “Brief explanation of drawings” column No. 1 of the description
On the 9th line of page 6, correct the text r14a, 14b, 14c J to r14a, 14b, 14c, 14d J. 6-3 Figure 1 of the drawing is corrected as shown in the attached sheet. 7. One copy of the catalog correction drawing of the attached documents

Claims (1)

[Claims] (1) In an IC card that transmits and receives data to and from a device using radio waves, a resonant circuit consisting of a combination of a single coil and multiple capacitors or a combination of multiple coils and a single capacitor; and the capacitor or coil. and a switching means for selectively switching the resonant circuit, wherein the resonant frequency of the resonant circuit is used as a carrier wave of the radio wave.