JPH1188242A - 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 circuit 37 connects to a transmission reception coil 31 of a responder 30 via a switching transistor(TR) 39, and the resistance of the transmission load circuit 37 is selected so that the circuit 37 consumes power nearly equal to transmission power consumed to transmit data at a maximum communication distance (or a communication limit distance) with an interrogator 10. An internal processing circuit 35 activates the TR 39 via an I/O in the case that the responder 30 is operated with small power consumption in the vicinity of the limit communication distance so as to allow the transmission load circuit 37 to consume power, thereby suppressing an output of a rectifier circuit 33. In the case that the responder 30 required much power as data transmission or the like, the circuit 35 inactivates the TR 39. The TR 39 is conductive when a modulation circuit 36 provides an output of data '1'.

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.

[0004]

By the way, the electric power used in the transponder generates an induced voltage in the coil by the high frequency magnetic field supplied from the interrogator, and rectifies the induced voltage by the rectifier circuit and supplies it. The data carriers are roughly divided into: 1. A state in which no operation is performed without receiving a high-frequency magnetic field; 2. A receiving operation state for receiving a modulated signal applied to this signal together with a high-frequency magnetic field from the interrogator; 3. Internal processing state in which signal processing is performed in the transponder while receiving a high-frequency magnetic field from the interrogator; There are four operating states: a transmitting operation state in which data is transmitted to the interrogator while receiving a high-frequency magnetic field from the interrogator.

[0005] Among them, the fourth transmission operation state is the operation state that consumes the most power as a transponder. When the distance between the interrogator and the transponder is long, the power received from the interrogator is small, and only the power close to the lower limit for the operation of the transponder can be obtained, the power consumption of the transponder differs depending on the above four operation states. That could be an obstacle.

A data carrier system usually operates in the following procedure in many cases. (1) The transponder starts operating in response to a high-frequency magnetic field and a signal from the interrogator, and transmits a short signal for notifying that the transponder has arrived in the communication area in response to the call from the interrogator. . (2) The interrogator recognizes that the transponder has arrived in the communication area, and confirms the ID and sends an inquiry command for internal data of the transponder.

(3) The transponder performs a process in accordance with the command from the interrogator, and performs a process of continuously returning the corresponding data to the interrogator. In this series of processing, the responding machine consumes the most power during the transmission to the interrogator,
The power consumed when transmitting a short signal such as the response of (1) can be sufficiently covered by the electric charge accumulated in the smoothing capacitor provided in the rectifier circuit of the transponder. When transmitting data continuously, large power is required.When the distance between the transponder and the interrogator is close to the response limit, the amount of charge accumulated in the smoothing capacitor is not enough, and the transponder is smoothed. There is a problem in that the charge accumulated in the capacitor is used up and the operation stops during data transfer.

This problem is particularly problematic in the case of a multi-support data carrier system that supports a plurality of transponders with one interrogator. 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. To solve this problem, consider a method of increasing the size of the smoothing capacitor or dividing the transmission data for a sufficiently short period with the charge stored in the smoothing capacitor and transmitting it, and charging the smoothing capacitor during the divided transmission. However, the former has another problem that the size of the transponder increases and the cost also increases.The latter has a long time in exchanging data with one transponder and is used for applications such as transport systems. In such a case, there is a problem that the moving speed of the object attached to the transponder in the transport system must be limited.

An object of the present invention is to solve the above-mentioned problems and to provide a data carrier capable of securing a sufficient transmission power when the transponder operates near a communication distance limit.

[0010]

In order to achieve the above object, a data carrier according to the present invention comprises a transmitting / receiving coil, a tuning capacitor connected thereto, a rectifying circuit for rectifying a signal received by the transmitting / receiving coil, and a rectifying circuit. An internal processing circuit driven by the output power of, and a transmission circuit for supplying a transmission signal to the transmission and reception coil, in a data carrier that performs signal processing according to the instruction from the interrogator, data at the maximum communication distance with the interrogator And a load circuit for the rectifier circuit with a power consumption substantially equal to the transmission power consumed for transmitting the power, and when the power consumption in the internal processing circuit is small, the load circuit is connected to the rectifier circuit and the power in the internal processing circuit is connected. A switching means for disconnecting when the consumption is large is provided.

The load circuit can be shared with a transmission load circuit for applying amplitude modulation to the voltage between both ends of the transmission / reception coil in order to transmit data from the data carrier to the interrogator.

[0012]

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 an 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. 12, a selection circuit 15 for selecting and outputting one carrier from the first and second carriers, 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,
It includes a rectifier circuit 33, a demodulation circuit 34 for performing FSK demodulation, an internal processing circuit 35, a transmission modulation circuit 36, and a transmission load circuit 37. The internal processing circuit 35 includes a CPU 35a, a RAM 35b, a ROM 35c storing programs and the like, an electrically rewritable EEPROM 35d, and an interface 35e, like a general signal processing circuit. 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 output of the transmission modulation circuit 36 and the output of the interface 35 e are connected to a switching transistor 39 via a logical OR circuit 38. The switching transistor 39 selectively connects the transmission load circuit 37 to the contact between the transmission / reception coil 31 and the rectifier circuit 33 according to the output of the logical OR circuit 38. The resistance value of the transmission load circuit 37 is set such that the power consumption is substantially equal to the transmission power consumed for transmitting data at the maximum communication distance (or communication limit distance) with the interrogator 10.

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 selecting 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”.

When data is transmitted from the transponder 30 to the interrogator 10, the data generated by the CPU inside the internal processing circuit 35 is transmitted to the modulation circuit 3 via the interface 35e.
6, the switching transistor 39 of the transmission load circuit 37 is turned on / off in accordance with 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, the demodulation operation is performed by a band-pass filter by detecting the change in the amplitude and phase of the sub-band of the 125 KHz signal output from the first frequency divider 14.

The internal processing circuit 35 connects a load circuit to the rectifier circuit when the power consumption inside the internal processing circuit 35 is small, and disconnects a control signal for disconnecting when the power consumption in the internal processing circuit is large via the interface 35e. Output. When the power consumption is large, operations such as data writing to the electrically rewritable EEPROM 35d and a data transmission operation are performed.

When the power consumption inside the internal processing circuit 35 is small, the switching transistor 39 is turned on, and the load circuit 37 is connected to the transmission / reception coil 31 of the tuning circuit. At 37, the heat is consumed, and the current flowing through the rectifier circuit 33 decreases, and the power supplied to the internal processing circuit 35 decreases. Here, when performing a data transmission operation with a large power consumption, a control signal for turning off the switching transistor 39 is output via the interface 35e. However, the modulation circuit 36 outputs a signal that turns on the switching transistor 39 when the transmission data is logic “1” and turns off when the transmission data is logic “1”.
The switching transistor 39 performs an on / off operation according to a signal from the modulation circuit 36.

At this time, the resistance value of the load circuit 37 is determined by the interrogator 1.
Since the power consumption is set to be substantially equal to the transmission power consumed for transmitting data at the maximum communication distance (or communication limit distance) with 0, even if the load circuit is connected to the tuning circuit. The power supplied from the rectifier circuit 33 does not fall below the power required for data transmission. still,
The present invention is based on the premise that the distance between the interrogator 10 and the transponder 30 is as close as possible to the communication limit.
A situation occurs in which the output rise of the rectifier circuit 33 cannot be suppressed only by the power consumption of the load circuit 37 when the internal power consumption is small. This means that the resistance value of the load circuit 37 is
This is because the power consumption is set to be substantially equal to the transmission power consumed for transmitting data at the maximum communication distance (or communication limit distance) between the interrogator 10 and the responder 30. This is because the load is too small when the distance is short.

In order to prevent this situation, as a modified example of the present embodiment, as shown in FIG. 2, a voltage detecting means 41 for detecting an output voltage of the rectifying circuit 33 and the voltage detecting means 41 are set in advance. The tuning circuit includes a load circuit 43 connected via the switching transistor 42 when a voltage exceeding the threshold voltage is detected. Load circuit 42
As a result, when the distance between the interrogator 10 and the transponder 30 becomes a short distance, a current bypass is formed, and a part (a large part of the current) generated in the tuning circuit is supplied to the load circuit 4.
In step 2, the heat is consumed as heat and the current to the rectifier circuit 33 is limited.

Therefore, within the limit response distance, a stable operation can be performed regardless of the distance between the interrogator 10 and the transponder 30.

[0023]

As described above, according to the present invention, it is possible to provide a data carrier that can secure 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 system according to an embodiment of the present invention.

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

[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 Circuit 38 OR circuit

Claims (3)

[Claims] A transmitting / receiving coil, a tuning capacitor connected thereto, a rectifying circuit for rectifying a signal received by the transmitting / receiving coil, an internal processing circuit driven by output power of the rectifying circuit, A transmission circuit for supplying a signal to the transmission / reception coil, and in a data carrier that performs signal processing in accordance with an instruction from the interrogator, a power consumption substantially equal to a transmission power consumed for transmitting data at a maximum communication distance with the interrogator. A load circuit for the rectifier circuit, and switching means for connecting the load circuit to the rectifier circuit when the power consumption in the internal processing circuit is small, and disconnecting the load circuit when the power consumption in the internal processing circuit is large. A data carrier characterized by the following: 2. The transmission circuit according to claim 2, wherein the load circuit is used for transmitting data from a data carrier to the interrogator, and is used as a transmission load circuit for applying amplitude modulation to a voltage between both ends of the transmission / reception coil. A data carrier characterized by being performed. 3. A transmission / reception coil, a tuning capacitor connected thereto, a rectification circuit connected to both ends of the transmission / reception coil for rectifying a signal received by the transmission / reception coil, and an internal part driven by output power of the rectification circuit. A processing circuit, and a transmission circuit that supplies a transmission signal to the transmission / reception coil,
In a data carrier that performs signal processing according to an instruction from the interrogator, a load circuit for the rectifier circuit having a power consumption substantially equal to a transmission power consumed for transmitting data at a maximum communication distance with the interrogator; When the power consumption in the internal processing circuit is small, the load circuit is connected to the rectifier circuit, and when the power consumption in the internal processing circuit is large, a load control unit that generates a load control signal to disconnect the load circuit, A data carrier, comprising: logic means for generating a logical sum signal of an output and a load control signal; and switching means for connecting the load circuit to the rectifier circuit in accordance with the output of the logic means.