JPH1188243A - Data carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a responder to obtain sufficient transmission power even when the responder is in operation in the vicinity of communication coverage limit. SOLUTION: A transmission load transistor(TR) 37 and a voltage adjustment load TR 38 connect to a transmission reception coil 31 of a responder 30. A voltage detection circuit 40 activates the voltage adjustment load TR 38 when a voltage across the transmission reception coil 31 is high to form a bypass and to suppress the voltage. In the case of conducting data transmission, an internal processing circuit 35 opens a switch 39 or when transmission data are logical '1', the circuit 35 closes the switch 39 to connect the voltage detection circuit 40 and a gate of the voltage adjustment load TR 38, and when transmission data are logical '0', the circuit 35 opens the switch 39. When the transmission data are logical '1', the TR 37 is conductive and when the transmission data are logical '0', the TR 37 is nonconductive. Thus, the TR 38 is operated in the same manner as the TR 37.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data carrier and, more particularly, to a non-contact type IC card type data carrier for exchanging signals between an interrogator and a transponder (data carrier).

[0002]

2. Description of the Related Art A data carrier system (for example, a "non-contact IC") for transmitting and receiving signals between an interrogator and a card of an answering machine by an electromagnetic coupling system or an electromagnetic induction system.
Practical application as a "card system") is widely known. In particular, the carrier is rectified on the transponder side,
Battery-free non-contact IC used as power for transponders
A card system has been widely used as an ID card, a tag for recognizing a conveyed article, and the like.

In such an electromagnetic coupling type non-contact IC card system, the interrogator is an OSC (oscillator).
Is modulated according to the transmission data, the modulated wave is amplified by a driver circuit, and the antenna coil is driven and transmitted to the transponder. When the transponder receives the signal from the interrogator with the antenna coil, the rectifier circuit rectifies the carrier wave to obtain the power to be used internally, and the demodulation circuit demodulates the received signal and sends it to the data processing circuit for data processing. Data processing is performed by the circuit. FIG. 3 shows an example of a conventional data carrier system.

The power used by the transponder is generated by rectifying a signal received from the interrogator by a rectifier circuit. The power obtained is the distance between the antenna coil 31 of the transponder and the antenna coil 17 of the interrogator. It changes according to. Generally, when the distance between the antenna coil 31 of the transponder and the antenna coil 17 of the interrogator is shorter, a larger induced electromotive force can be obtained.

In order to increase the communicable distance, the size of the antenna coil and the magnitude of the transmission power at the interrogator are set so that sufficient power can be obtained at the maximum communicable distance. Then, there arises a problem that when the distance between the antenna coil 31 of the transponder and the antenna coil 17 of the interrogator is short, the power obtained becomes too large and the withstand voltage of the element in the data carrier must be increased.

Conventionally, in order to solve this problem, the output of the rectifier circuit is monitored using a voltage detection circuit 40, and when the output of the rectifier circuit exceeds a predetermined voltage, an overvoltage protection is applied to the input of the rectifier circuit. The overload protection circuit 38 'is connected, and the reception signal current is supplied to the overvoltage prevention load circuit 38' and consumed as heat, thereby preventing overvoltage.

When data is transmitted from the data carrier to the interrogator, a transistor 37 as a variable load means is connected in parallel with the antenna coil 31 of the transponder, and this transistor is driven by the transmission data to thereby transmit the antenna coil. The data is transmitted by changing the current flowing through the antenna 31 and changing the coupling state between the antenna coil 31 and the antenna coil 17 of the interrogator.

[0008] Antenna coil 31 as a power supply of the transponder
This means that two load circuits, ie, the load for transmission and the above-mentioned load circuit for overvoltage prevention are connected as loads.

[0009]

When transmitting data, several times more power is consumed than during normal data processing. Normally, this electric power is covered by the electric charge stored in the smoothing capacitor 33b of the rectifier circuit 33, but the voltage detection circuit 40 for controlling the overvoltage prevention load circuit 38 'generates a voltage higher than the voltage required for normal data processing. When the overvoltage protection load circuit 38 'is in the active state and the mode is switched to the data transmission mode, the electric charge accumulated in the smoothing capacitor is not sufficient to maintain the data transmission. Sometimes, during the data transmission, there is a danger of power shortage and communication stop. In particular, when the distance between the interrogator and the transponder is close to the response limit distance, the charge accumulated in the smoothing capacitor 33b is sufficient for normal data processing. Become.

This problem is particularly problematic in the case of a multi-support data carrier system in which a single interrogator supports a plurality of transponders. This is because, if at least one such transponder exists, a phenomenon occurs that the entire system stops because data transmission requests are repeated many times for this transponder. In order to solve this problem, a method of increasing the size of the smoothing capacitor 33b or dividing the transmission data for a sufficiently short period with the electric charge stored in the smoothing capacitor 33b and transmitting the divided data and charging the smoothing capacitor during the divided transmission is used. However, the former has another problem that the size of the transponder increases and the cost increases.The latter has a long time for exchanging data with one transponder, and is used for transport systems. In such a case, a problem arises in that the moving speed of the object attached to the transponder in the transport system must be limited.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a data carrier capable of securing a sufficient transmission power when a transponder operates near a communication distance limit.

[0012]

A data carrier according to the present invention for achieving the above object comprises a tuning circuit having a transmitting / receiving coil and a tuning capacitor connected thereto, and a signal generated at an output terminal of the tuning circuit. A rectifier circuit for rectifying, a voltage detecting means for detecting an output voltage of the rectifier circuit, a signal processing circuit which is supplied with power by an output of the rectifier circuit and outputs a transmission signal, and a control signal input to a control signal input terminal. First load means for applying a corresponding load to the output terminal of the tuning circuit, second load means for applying a load corresponding to the transmission signal to the output terminal of the tuning circuit, and selectively according to the logical value of the transmission signal. Switching means for supplying an output of the voltage detection means to a control signal input terminal of the first load means.

When the transponder operates near the communication distance limit, the output voltage of the rectifier circuit decreases, and the voltage detecting means detects the decrease of the output voltage and increases the impedance of the first load means. The load of the first load means is reduced, the power consumption of the first load means is reduced, and operations with large power consumption such as data transmission can be performed.

In one embodiment, the switching means supplies the output of the voltage detecting means to the control signal input terminal of the first load means when the transmission signal indicates one logical value, and indicates the other logical value. In such a case, a signal for disabling the first load means is supplied. Here, the second load means increases the load when the transmission signal of one logical value is supplied, and decreases the load when the transmission signal of the other logical value is supplied.
By doing so, the first load means can also be used as a load for data transmission, and more efficient data transmission becomes possible.

[0015]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a data carrier system using a data carrier according to the first embodiment of the present invention. In the figure, an interrogator 10 includes an oscillating circuit 11 for generating a basic signal of a carrier, and a frequency dividing circuit for dividing the basic signal from the oscillating circuit 11 at different frequency division ratios to generate first and second carrier waves. A selection circuit 15 for selecting and outputting one carrier from the first and second carriers 12 and 13;
And an output amplifier 16, an antenna coil 17, and a tuning capacitor 18. The interrogator 10 further includes an internal processing circuit 19 for generating a transmission signal and a demodulation circuit 20 for processing a signal received by the antenna coil 17. In this figure, the input of the demodulation circuit 20 is the antenna coil 17, but a receiving coil may be separately provided concentrically with the antenna coil 17.

The transponder 30 includes a transmission / reception coil 31, a tuning capacitor 32 connected in parallel to the transmission / reception coil 31,
A rectifier circuit 33, a demodulation circuit 34 for performing FSK demodulation, an internal processing circuit 35, a transmission modulation circuit 36, a transmission load transistor 37, a voltage adjustment load transistor 38, a switch 39, a voltage detection circuit 40, and a voltage regulator circuit 41 Have. The internal processing circuit 35 includes a CPU 35a, a RAM 35b, a ROM 35c storing programs and the like, an electrically rewritable E
An EPROM 35d and an interface 35e are provided. The power rectified by the rectifier circuit 33 is supplied to a demodulation circuit 34, an internal processing circuit 35, and a transmission modulation circuit 36.

The oscillation circuit 11 generates a 4 MHz reference signal, for example. This reference signal is supplied to the first and second frequency dividers 1
2 and 13 and the signal (125 KHz) divided by the first frequency dividing circuit 12 to 1/32 and the second frequency dividing circuit 13
Divided by 1/34 (117.6470588)
KHz). The internal processing circuit 19 has a logical value “1”
When the transmission of the data is instructed, the selection circuit 15
And outputs a signal of 125 KHz to the antenna coil 17 via the output amplifier 16. On the other hand, when the internal processing circuit 19 instructs the transmission of data of the logical value “0”, the output of the second frequency dividing circuit 13 is selected by the selecting circuit 15 and the signal of 117.6470588 KHz is transmitted through the output amplifier 16. To the antenna coil 17.

After the data transmission, the output of the first frequency dividing circuit 12 is selected by the selection circuit 15 for power transmission to the transponder, and
The signal of 25 KHz is continuously sent to the antenna coil 17 via the output amplifier 16. Transceiver coil 31 of transponder 30
The tuning frequency of the tuning circuit composed of the tuning capacitor 32 is 125 KHz and 117.6470588 KHz.
Center of the two frequencies, ie, the root (125 kHz × 1)
17.6470588) = 121.2678125KH
z. Therefore, the transponder 30 can receive a signal of almost the same strength both when receiving the logical value “1” and when receiving the logical value “0”.

The power in the transponder 30 is used by converting a carrier wave received by a tuning circuit composed of a transmitting / receiving coil 31 and a tuning capacitor 32 into a direct current by a diode 33a and a smoothing capacitor 33b of a rectifier circuit 33. A voltage regulator 41 is provided to further stabilize the voltage used in the internal processing circuit 35. The voltage detection circuit 40 detects the output voltage of the rectifier circuit 33.

When data is transmitted from the transponder 30 to the interrogator 10, data generated by the CPU inside the internal processing circuit 35 is transmitted to the modulation circuit 3 via the interface 35e.
6 to turn on / off the transmission load transistor 37 according to the output of the modulation circuit. Then, the current flowing through the transmitting / receiving coil 31 changes, and the strength of the electromagnetic coupling between the transmitting / receiving coil 31 and the antenna coil 17 changes. The demodulation circuit 20 of the interrogator 10 detects a change in the voltage generated at both ends of the antenna coil 17, specifically, a change in the amplitude of the 125 KHz signal output from the first frequency divider 14, and Demodulate the data. Actually, it is a bandpass filter, and 125 output from the first frequency dividing circuit 14 is output.
The demodulation operation is performed by detecting changes in the amplitude and phase of the sub-band of the KHz signal.

When the distance between the transponder 30 and the interrogator 10 is relatively short, the switch 39 connects the voltage detection circuit 40 to the gate end of the voltage adjustment load transistor 38. The voltage detection circuit 40 detects the output voltage of the rectifier circuit 33, and operates the voltage adjustment load transistor 38 when the output voltage of the rectifier circuit 33 becomes equal to or more than a predetermined value. Rectifier circuit 3
3. The current flowing through 3 is limited to suppress an increase in voltage.

The internal processing circuit 35 switches the switch 39 at the time of data transmission so that the voltage adjusting load transistor 38
Turn off. As a result, the voltage at both ends of the tuning circuit composed of the transmitting and receiving coil 31 and the tuning capacitor 32 is maintained, and sufficient power for transmission can be secured. When the voltage between the transponder 30 and the interrogator 10 is relatively short and the voltage generated by the tuning circuit is high, the switch 39 is switched to disconnect the voltage detection circuit 40. As a result, the detection output of the voltage detection circuit 40 is taken into the internal processing circuit 35 via the interface 35e, and the output of the voltage detection circuit 40 becomes a constant value, as indicated by a dotted line in FIG. In this case, the switch 39 is not switched.

Alternatively, as shown in FIG. 2, a voltage adjustment load transistor 42 at the time of high voltage is separately provided, and when the output voltage of the tuning circuit is high, a load with lower impedance (voltage adjustment load transistor 42) is tuned. When the output voltage of the tuning circuit is relatively low, a load having a relatively high impedance (the voltage adjustment load transistor 38) may be connected to the output terminal of the tuning circuit. .

As described above, according to this embodiment, the problem that the voltage adjusting load transistor 38 for voltage limitation operates during data transmission and power required for the transmission operation cannot be obtained does not occur. Next, a second embodiment of the present invention will be described. Since the configuration of the second embodiment of the present invention is the same as that of the first embodiment, it will be described with reference to FIG. In the first embodiment, the internal processing circuit 35 switches the switch 39 at the time of data transmission to turn off the load transistor 38 for voltage adjustment. However, in the present embodiment, the internal processing circuit 35 switches the switch 39 at the time of data transmission. Is switched to connect the voltage detection circuit 40 to the gate end of the voltage adjusting load transistor 38 when the transmission data is logic "1", and open when the transmission data is logic "0". The transmission load transistor 37 is also turned on when the transmission data is logic “1”, and the transmission data is logic “0”.
It operates to turn off in the case of. Therefore, when the transmission data is logic “1”, the transmission load is the transistor 3
7 and the impedance of the parallel circuit of the transistor 38, which is smaller than the impedance of the transmission load transistor 371, the voltage change between both ends of the transmission and reception coil 31 can be increased, and stronger AM modulation can be applied. I can do it.

As described above, according to this embodiment, the problem that the voltage adjusting load transistor 38 for voltage limitation operates during data transmission and the power required for the transmission operation cannot be obtained does not occur. Since the adjustment load transistor 38 is also used as a transmission load, a stronger AM
Modulation can be applied, and the data transmission distance can be extended.

[0026]

According to the present invention, it is possible to provide a data carrier capable of securing a sufficient transmission power when the transponder operates near the communication distance limit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a data carrier according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a modification of the data carrier according to the embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional data carrier.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 Interrogator 11 Oscillator 12 Frequency divider 13 Frequency divider 15 Selection circuit 17 Antenna coil 18 Tuning capacitor 19 Internal processing circuit 20 Demodulation circuit 30 Transponder 31 Transceiver coil 32 Tuning capacitor 33 Rectifier circuit 35 Internal processing circuit 37 Transmission load Transistor 38 Load transistor for voltage adjustment 39 Switch 40 Voltage detection circuit 41 Voltage regulator

Claims (4)

[Claims] 1. A transmission / reception coil, a tuning capacitor connected thereto, a rectification circuit for rectifying a signal received by the transmission / reception coil, and a transmission signal driven by output power of the rectification circuit to supply a transmission signal to the transmission / reception coil. A transmission circuit, a voltage detection circuit that detects a rectified voltage, a bypass transistor that connects between input terminals of the rectification circuit, and changes a current that flows according to an output of the voltage detection circuit, and a logical value of the transmission signal. A data switching means for switching supply of the output of the voltage detection circuit to the bypass transistor in accordance with the data carrier. 2. A tuning circuit having a transmitting / receiving coil and a tuning capacitor connected thereto, a rectifying circuit for rectifying a signal generated at an output terminal of the tuning circuit, and a voltage detection detecting an output voltage of the rectifying circuit. Means, a signal processing circuit that is supplied with power by an output of the rectifier circuit and outputs a transmission signal, and a first circuit that applies a load corresponding to a control signal input to a control signal input terminal to an output terminal of the tuning circuit. Load means; second load means for applying a load corresponding to the transmission signal to an output terminal of the tuning circuit; and the control signal input of the first load means selectively according to a logical value of the transmission signal. A switching means for supplying an output of the voltage detecting means to a terminal. 3. The switching means according to claim 2, wherein said switching means supplies an output of said voltage detecting means to said control signal input terminal of said first load means when said transmission signal indicates one logical value, and A data carrier for supplying a signal for disabling the first load means when the logical value indicates 4. The apparatus according to claim 3, wherein the second load means increases a load when the transmission signal of the one logical value is supplied, and increases the load when the transmission signal of the other logical value is supplied. A data carrier characterized by reducing the load.