JPH03209589A - Transmitting / receiving system - Google Patents

Abstract

PURPOSE:To reduce the number of magnetic coupling circuit to be used and to eliminate the necessity of an oscillation circuit required for signal transmission and reception only by one of transmitters / receivers by totally transmitting plural signals through one magnetic coupling circuit. CONSTITUTION:At a reader / writer 1, a power supply voltage is impressed from a power supply circuit 3 to respective circuits. An oscillation circuit 5 outputs the carrier of 1MHz frequency for example and supplies the carrier to an amplitude modulation circuit 7. The carrier to be outputted from the amplitude modulation circuit 7 is sent through the magnetic coupling circuit composed of a transmission coil 9 and a reception coil 10 to an IC card 2 and converted to a direct current voltage as the power supply voltage by a rectifying / smoothing circuit 16. This power supply voltage is impressed to the respective circuits in the IC card 2 and power is applied to these circuits and supplied from the reader / writer 1 to the IC card 2. Thus, the number of transmission / reception channels is reduced and circuit constitution for transmission / reception is simplified.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a transmission/reception method between two transmitting/receiving devices such as an IC card and its reader/writer. This relates to the transmission and reception method resulting from the combination.

[Conventional technology]

In recent years, IC cards that have built-in IC circuits such as memory and can store large amounts of data have been attracting attention.

When storing data on such an IC card or reading data from such an IC card, the IC card is attached to a reader/writer, but this attachment causes the electrical contacts provided on the IC card to connect with the electrical contacts on the reader/writer. These IC cards and the reader/writer are electrically connected.

By the way, in such an IC card, the above-mentioned electrical contacts are mounted and exposed to the outside.

Generally, such IC cards are always carried by the user, and therefore dust and the like tend to adhere to the electrical contacts and static electricity is generated. If dust or the like adheres to the electrical contacts, the contact between the IC card and the reader/writer will become poor, and if static electricity is generated at the electrical contacts of the IC card, the IC circuit inside the IC card will be damaged. A voltage may be applied and this IC circuit may be destroyed.

As a method to solve this problem, a method is known in which an IC card is connected to a reader/writer by magnetic coupling (for example, Japanese Patent Application Laid-open No. 18639/1983).
No. 2 public i1ri.

This is because the reader/writer is provided with two coils, an oscillating coil and a receiving coil, and the IC card is provided with a metal loop of at least one turn, and when the IC card is attached to the reader/writer, this metal loop becomes the oscillating coil. It is inserted between the receiving coil and the receiving coil. A sine wave of constant amplitude is supplied to the oscillating coil from the oscillating circuit, and due to electromagnetic induction between the oscillating coil and the receiving coil,
This sine wave is output from the receiving coil. Furthermore, an electronic switch is provided in the IC card to turn on or off depending on the logical state of the data (1" or 0" bits) to short-circuit or release the metal loop. When the metal loop is inserted between the oscillating coil and the receiving coil and the electronic switch is off, no eddy current is generated in the metal loop, so the receiving coil is not affected by the metal loop. The receiving coil receives magnetic flux from the oscillating coil, and a large amplitude sine wave is output from the receiving coil. On the other hand, when the electronic switch is on, an eddy current is generated in the metal loop, and the amount of magnetic flux received by the receiving coil is reduced by the magnetic flux caused by this eddy current.

Therefore, the amplitude of the sine wave output from the receiving coil becomes small.

In this way, the amplitude of the sine wave output from the receiving coil changes depending on the 1'' and ''01 bits of the data in the IC card, and the data in the IC card can be obtained by amplitude detection of this sine wave. .

[Problem to be solved by the invention]

As described above, data transmission between an IC card and a reader/writer is also possible by magnetically coupling them.

However, in an IC card system, it is not only necessary to transmit data from the IC card to the reader/writer, but also to transmit data from the reader/writer to operate the IC card.
It is necessary to send power and clock to the C card, and
In order to write data to the IC card, it is necessary to send data from the reader/writer to the IC card, and a magnetic coupling circuit like the above-mentioned conventional technology is required for each IC card.

Moreover, at least for data transmission from a reader/writer to an IC card, when using the above-mentioned conventional technology, an oscillation coil, a reception coil, and an oscillation circuit that supplies a sine wave to this oscillation coil are attached to the IC card using a metal loop. It is necessary to provide the reader/writer with an electronic switch and an electronic switch.

In this way, a large number of coils are required, which are larger than the electrical contacts, and it is also necessary to provide an oscillation circuit with a complex configuration inside the IC card, which is not required with conventional IC cards that have electrical contacts. Therefore, the small size of IC card,
There is a problem in that it hinders thinning.

SUMMARY OF THE INVENTION An object of the present invention is to provide a transmission/reception system that solves these problems, reduces the number of transmission/reception channels, and simplifies the circuit configuration for transmission/reception.

[Failure to solve the problem]

In order to achieve the above object, the present invention magnetically couples a first and a second transmitting/receiving device by a first magnetic coupling circuit, and the first transmitting/receiving device receives a first signal of a constant amplitude. The first magnetic coupling circuit and the input terminal of the first received signal detection circuit are connected to the output terminal of the first oscillation circuit that outputs the oscillation circuit. The input terminal of the waveform shaping circuit is connected to a variable load impedance circuit whose load impedance changes depending on the level of the second signal.

Furthermore, the present invention provides the first aspect of the invention. The second transmitter/receiver is further magnetically coupled by a second magnetic coupling circuit in a non-contact manner;
In the first transmitting/receiving device, a second transmitting and receiving device generates a third signal.
an oscillation circuit, and a modulation circuit that modulates the third signal with a fourth signal and supplies it to the second magnetic coupling circuit, and the second magnetic coupling circuit is connected to the second transmitting/receiving device. a circuit that is supplied with the third signal transmitted through the circuit and generates the power supply voltage; and a circuit that is supplied with the third signal transmitted through the second magnetic coupling circuit and generates the fourth signal. A second received signal detection circuit is provided.

[Effect]

The output signal of the first oscillation circuit is supplied to the first received signal detection circuit via the first magnetic coupling circuit, but at the same time, when the load impedance of the variable load impedance circuit changes due to the second signal, The impedance of the first magnetic coupling circuit as seen from the first transmitting/receiving device side changes,
The level of the input signal of the first received signal detection circuit changes. A second signal is obtained by detecting this level change.

Further, since the third signal is modulated with the fourth signal and transmitted to the second transmitting/receiving device, the fourth signal is obtained by demodulating this third signal.

Moreover, by rectifying and smoothing this third signal, a DC voltage is obtained, which is used as the power supply voltage of the second transmitting/receiving device.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the transmitting/receiving system according to the present invention, in which 1 is a beam and a data writer, 2 is an IC card,
3 is a power supply circuit, 4 is a data processing circuit, 5.6 is an oscillation circuit, 7 is an amplitude modulation circuit, 8 is an amplitude detection/comparison circuit, 9 is a transmitting coil, 10 is a receiving coil, 1). 12 is a transmitting/receiving coil, 13 is an amplitude detection circuit, 14 is a waveform shaping circuit, 15 is a variable load impedance circuit, 16 is a rectification/smoothing circuit,
17 is a data processing circuit.

In the figure, a reader/writer 1 has a transmitting coil 9 and a transmitting/receiving coil 1), and an IC card 2 has a receiving coil 10 and a transmitting/receiving coil 12.

When the IC card 2 is attached to the reader/writer 1, the transmitting coil 9 and the receiving coil 10 are magnetically coupled in a non-contact state.
Similarly, transmitting/receiving coil 1). 12 are magnetically coupled in a non-contact manner.

In such a state, in the reader/writer 1, the power supply circuit 3
Power supply voltage is applied to each circuit from

The oscillation circuit 5 outputs a carrier wave having a frequency of, for example, IMHz, and supplies it to the amplitude modulation circuit 7. The carrier wave output from the amplitude modulation circuit 7 is sent to the IC card 2 via a magnetic coupling circuit consisting of a transmitter coil 9 and a receiver coil 10, and is converted into a DC voltage as a power supply voltage by a rectifier/smoothing circuit 16. . This t'/fA voltage is applied to each circuit within the IC card 2, giving power to these. In this way, power is supplied from the reader/writer 1 to the IC card 2.

Furthermore, when writing data to or reading data from the IC card 2, the oscillation circuit 6 outputs a signal of, for example, 4.9152 MHz in response to a command from the data processing circuit 4, which is a microprocessor or the like. This signal is supplied to the IC card 2 via a magnetic coupling circuit consisting of a transmitting/receiving coil 1) 12, and is waveform-shaped by a waveform shaping circuit 14 to generate a clock. This clock is a data processing circuit 17 consisting of a microprocessor, memory, etc.
It is used for writing data to memory, reading data from memory, etc.

Therefore, when writing data to the IC card 2, the data to be written is output from the data processing circuit 4, and the amplitude modulation circuit 7 amplitude modulates the carrier wave output from the oscillation circuit 5 using this data. In the IC card 2, this carrier wave received by the receiving coil 10 is supplied to the rectifier/smoothing circuit 16 as described above to be converted into a power supply voltage, and is also supplied to the amplitude detection circuit 13 where it is amplitude detected. The data is demodulated. This data is data processing circuit 1
7, and writing to memory is performed.

Note that the above-mentioned data includes not only information data to be written into the memory, but also write and read command data, and address data specifying the address of the memory, which are sent in a time-division manner.

Further, the carrier wave received by the receiving coil 10 is modulated with data and its amplitude fluctuates, but the rectifier/smoothing circuit 16
The amplitude of the carrier wave output from the oscillation circuit 5 is set so as to stably generate a power supply voltage with the amplitude necessary to operate each circuit of the card 17.

Furthermore, when writing data to the IC card 2, the data processing circuit 17 sets the impedance of the variable load impedance circuit 15 to a constant value so that a signal with a large constant amplitude can be obtained from the transmitting/receiving coil 12. .

When reading data from the IC card 2, as in the case of data writing, a carrier wave whose amplitude is modulated by reading command data and address data is received from the receiving coil 10, and an output signal of the oscillation circuit 6 is received from the transmitting/receiving coil 12. Further, the data processing circuit 17 switches the load impedance of the variable load impedance circuit 15 in accordance with "1" and "0" bits of data read from a memory (not shown).

When the load impedance of the variable load impedance circuit 15 is switched, the eddy current generated in the transmitter/receiver coil 12 changes, thereby causing the transmitter/receiver coil 1). The impedance of the 12 magnetic coupling circuits seen from the transmitting/receiving coil 1) side changes. Here, the output signal of the oscillation circuit 6 is also supplied to the amplitude detection/comparison circuit 8, and when the impedance seen from the transmitting/receiving coil 1) changes, the current flowing through the transmitting/receiving coil 1) changes, and along with this, Amplitude detection/
The current flowing through the comparator circuit 8 also changes. This change in current corresponds to "1" of the data supplied from the data processing circuit 17 to the variable load impedance circuit 15 in the IC card 2,
In the amplitude detection/comparison circuit 8, the supplied current is converted into a voltage, the amplitude of the voltage is detected and compared with a predetermined reference voltage, and the data is demodulated. This data is taken into the data processing circuit 4.

At this time, the amplitude of the input signal to the waveform shaping circuit 140 changes according to the change in the load impedance of the variable load impedance circuit 15, but the oscillation circuit 6 output signal amplitude and variable load impedance circuit 15
The value of the load impedance taken by the device is set.

Figure 2 shows the variable load impedance circuit 1 in Figure 1.
5, 18 is an electronic switch such as an FET, 19 is a resistor, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In the figure, the variable load impedance circuit 15 is composed of an electronic switch 18 and a resistor 19, and the electronic switch 18 receives data from the data processing circuit 17.
Turns on and off according to the 0” bit.Electronic switch 18
When turned on, it means that the transmitting/receiving coil 12 is short-circuited through the load impedance which is the resistor 19.
The impedance seen from the transmitting/receiving coil 1) side of the magnetic coupling circuit increases. As a result, the amplitude of the human input signal in the amplitude detection/comparison circuit 8 increases as shown in FIG.

When the electronic switch 18 is turned off, the resistor 19 ceases to act, the transmitting/receiving coil 12 is released, and the impedance seen from the transmitting/receiving coil 1) becomes small.

Therefore, the amplitude of the input signal of the amplitude detection/comparison circuit 8 is
As shown in FIG. 3, it becomes smaller.

When the electronic switch 18 is on, the input signal of the waveform shaping circuit 14 has a small amplitude and the electronic switch 18
When is off, the amplitude increases. The resistance value of the resistor 19 is set so that the waveform shaping circuit 14 can generate a clock by shaping the waveform of the human input signal even if the amplitude thereof is small.

Note that the resistor 19 can be omitted if an analog transistor whose input-output impedance can be switched between approximately infinite and a moderate value according to the control voltage is used as the electronic switch 18.

Further, as the oscillation circuit 6, it is desirable to use, for example, a push-pull oscillation circuit, which operates stably even if the impedance seen from the load, that is, the transmitting/receiving coil 1) side of the magnetic coupling circuit changes.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment.

That is, in FIG. 1, data transmission from the reader/writer 1 to the IC card 2 is carried out superimposed on a power carrier wave,
Data transmission from the IC card 2 to the reader/writer 1 was performed via a clock signal transmission line, but conversely, data transmission from the reader/writer 1 to the IC card 2 was performed by superimposing the clock signal, and a variable load was used. Data transmission from the IC card 2 using an impedance circuit to the reader/writer 1 may be performed via a power carrier wave transmission path. Furthermore, as shown in FIG. 1, the transmission of the power carrier wave and the clock signal is performed via separate magnetic coupling circuits, but these power carrier waves A half-duplex communication method may be used in which only one of the clock signal transmission paths is used.

Furthermore, as a power source for the IC card 2, energy such as solar cells or ultrasonic waves may be used instead of transmitting a power carrier wave from the reader/writer 1 as shown in FIG. A scientific battery may be built inside.

Furthermore, in the above embodiment, the target is an IC card and its reader/writer, but the application is not limited to this, but can also be applied to a device equipped with a data storage memory such as a memory card or a memory cartridge. It is also applicable to any system consisting of a plurality of transmitting/receiving devices that exchange data.

〔Effect of the invention〕

As explained above, according to the present invention, when transmitting and receiving a plurality of signals between at least two transmitting/receiving devices, the signals can be collectively transmitted via one magnetic coupling circuit, and the signals can be transmitted together through one magnetic coupling circuit. The number of parts used can be reduced, and the oscillation circuit required for signal transmission and reception can be eliminated in the transmitter/receiver, which simplifies and downsizes the configuration of the transmitter/receiver and reduces the number of parts. It is possible to improve reliability through reduction.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the transmitting/receiving system according to the present invention, FIG. 2 is a diagram showing an integrated example of the variable load impedance circuit in FIG. 1, and FIG. 3 is a block diagram showing an example of the variable load impedance circuit in FIG. It is a figure which shows a signal. ■...Reader/writer, 2...IC card, 3...Power supply circuit, 4...Data processing circuit, 5.6... Oscillation circuit, 7...
Amplitude modulation circuit, 8...Amplitude detection/comparison circuit, 9
......Transmission coil, 10...Reception coil, 1). 12... Transmitting/receiving coil, 13...
...Amplitude detection circuit, 14...Waveform shaping circuit, 1
5... Variable load impedance circuit, 1 6... Rectifier/smoothing circuit, 7... Data processing circuit.

Claims (5)

[Claims] (1) The first transmitting/receiving device and the second transmitting/receiving device are
In a transmission/reception method, the first and second transmitting/receiving devices are magnetically coupled in a non-contact manner by a magnetic coupling circuit, and signals are exchanged between the first and second transmitting/receiving devices via the first magnetic coupling circuit. In the transmitter/receiver, the first magnetic coupling circuit and the input terminal of the first received signal detection circuit are connected to the output terminal of the first oscillation circuit which outputs the first signal of constant amplitude. In the second transmitting/receiving device, the input terminal of the waveform shaping circuit and a variable load impedance circuit whose load impedance changes depending on the level of the second signal are connected to the first magnetic coupling circuit, and The first signal output from the oscillation circuit is transmitted to the waveform shaping circuit via the first magnetic coupling circuit, and at the same time the first signal is transmitted via the variable load impedance circuit and the first magnetic coupling circuit. A transmission/reception method characterized in that a second signal is transmitted to a first received signal detection circuit. (2) In claim (1), the first and second transmitting/receiving devices are further magnetically coupled by a second magnetic coupling circuit in a non-contact manner, and the first transmitting/receiving device is connected to the second magnetic coupling circuit. a second oscillation circuit that supplies a third signal to the coupling circuit;
The second transmitting/receiving device is supplied with the third signal transmitted through the second magnetic coupling circuit, and includes a circuit that generates a power supply voltage from the third signal. method. (3) In claim (2), modulation in which the third signal from the second oscillation circuit is modulated by a fourth signal to the first transceiver and supplied to the second magnetic coupling circuit. A circuit is provided, the third signal transmitted via the second magnetic coupling circuit is supplied to the second transmitting/receiving device, and a second received signal detection circuit is provided for detecting the fourth signal. A transmission and reception method characterized by: (4) In claim (1), (2) or (3), the second transmitting/receiving device includes an I/O device having at least a built-in memory.
C card, the first transmitting/receiving device is a data writing/reading device for the IC card, and the first and second
A transmitting/receiving method characterized in that each magnetic coupling circuit consists of a coil. (5) In claim (1), (2), (3) or (4), the first received signal detection circuit detects the first received signal according to a change in the load impedance of the variable load impedance circuit. A transmission/reception method characterized by detecting changes in the amplitude of an input signal caused by changes in impedance of a magnetic coupling circuit.