JP3862112B2 - Data carrier - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a data carrier, and more particularly to a non-contact type IC card type data carrier that exchanges signals between an interrogator and a responder (data carrier).
[0002]
[Prior art]
Practical use as a data carrier system (for example, “non-contact IC card system”) in which signals are exchanged between an interrogator and a responder card by an electromagnetic coupling method or an electromagnetic induction method, etc. ) Is widely known. In particular, battery-free non-contact IC card systems that rectify the carrier wave on the responder side and use it as power for the responder have come to be widely used as ID cards, tags for identifying transported items, etc. .
[0003]
In such an electromagnetic coupling type non-contact IC card system, the interrogator modulates the carrier wave generated by the OSC (oscillator) according to the transmission data, amplifies the modulated wave by the driver circuit, and the antenna coil. Is sent to the responder. When the transponder receives the signal from the interrogator with the antenna coil, the rectifier circuit rectifies the carrier wave to obtain power to be used internally, and the demodulator circuit demodulates the received signal and sends it to the data processing circuit for data processing. Data processing is performed by the circuit.
[0004]
[Problems to be solved by the invention]
By the way, the electric power used by the responder generates an induced voltage in the coil by a high-frequency magnetic field supplied from the interrogator, and rectifies and supplies this by a rectifier circuit.
The data carrier can be roughly divided into:
1. The state that does not receive any high frequency magnetic field and does not operate
2. A receiving operating state that receives a modulated signal applied to this signal together with a high-frequency magnetic field from an interrogator,
3. Internal processing state that performs signal processing in the responder while receiving a high-frequency magnetic field from the interrogator,
4). There are four operational states, a transmission operational state in which data is transmitted to the interrogator while receiving a high frequency magnetic field from the interrogator.
[0005]
Among these, the fourth transmission operation state is the operation state that consumes the most power as a responder.
When the distance between the interrogator and the answering machine is long, the power received from the interrogator is small, and only the power close to the lower limit for the operation of the answering machine can be obtained, the power consumption of the answering machine varies depending on the above four operation states. That could be an obstacle.
[0006]
A data carrier system usually operates in the following procedure.
(1) The responder starts operating upon receiving a high-frequency magnetic field and signal from the interrogator, and transmits a short signal informing that the responder has entered the communication area in response to a call from the interrogator. .
(2) The interrogator recognizes that the responder has come within the communication area, and sends an ID confirmation and an inquiry command for the internal data of the responder.
[0007]
(3) The responder performs processing in accordance with the command from the interrogator, and performs processing for continuously returning the corresponding data to the interrogator.
In this series of processes, the responder consumes the most power in the transmission operation to the interrogator. However, the power consumed in transmitting a short signal such as the response in (1) is the rectification of the responder. The charge stored in the smoothing capacitor provided in the circuit can be adequately covered, but when transmitting various data continuously as shown in (3), a large amount of power is required. If the distance is close to the response limit, the amount of charge stored in the smoothing capacitor is not enough, so the responder uses up the charge stored in the smoothing capacitor and stops operating in the middle of data transfer. There was a problem.
[0008]
This problem is particularly problematic in the case of a multi-compatible data carrier system that supports a plurality of responders with a single interrogator. This is because, even if there is such an unstable responder, a phenomenon occurs in which the entire system stops due to repeated data transmission requests to this responder.
To solve this problem, the smoothing capacitor can be enlarged, or the transmission data can be divided and transmitted for a sufficiently short period with the charge accumulated in the smoothing capacitor, and the smoothing capacitor can be charged during the divided transmission. However, the former causes another problem that the size of the responder increases and the cost also increases, and the latter has a long time for exchanging data with one responder, and is used for applications such as transport systems. In such a case, there is a problem that the moving speed of the object to which the responder in the transport system is attached must be limited.
[0009]
An object of the present invention is to solve the above problems and provide a data carrier that can secure sufficient transmission power when a responder operates near the communication distance limit.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a data carrier of the present invention includes a transmission / reception coil, a tuning capacitor connected to the transmission / reception coil, a rectifier circuit for rectifying a signal received by the transmission / reception coil, and an internal process driven by output power of the rectification circuit. A data carrier that includes a circuit and a transmission circuit that supplies a transmission signal to the transmission / reception coil, and that performs signal processing in accordance with an instruction from the interrogator. A load circuit for a rectifier circuit with a power consumption almost equal to the power, and a switching means for connecting the load circuit to the rectifier circuit when the power consumption in the internal processing circuit is small and to disconnect when the power consumption in the internal processing circuit is large Prepare.
[0011]
The load circuit can be used in common with a transmission load circuit for applying amplitude modulation to the voltage at both ends of the transmission / reception coil in order to transmit data from the data carrier toward the interrogator.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
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 oscillation circuit 11 that generates a basic signal of a carrier wave, and a frequency divider circuit that generates first and second carrier waves by dividing the basic signal from the oscillation circuit 11 with different division ratios. 12, a selection circuit 15 that selects and outputs one carrier wave from the first and second carrier waves, an output amplifier 16, an antenna coil 17, and a tuning capacitor 18. The interrogator 10 further includes an internal processing circuit 19 that generates a transmission signal and a demodulation circuit 20 that processes a signal received by the antenna coil 17. In this figure, the input of the demodulating circuit 20 is the antenna coil 17, but a receiving coil may be provided concentrically with the antenna coil 17.
[0013]
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 that performs FSK demodulation, an internal processing circuit 35, a transmission modulation circuit 36, and a transmission load. A circuit 37 is included. Like the general signal processing circuit, the internal processing circuit 35 includes a CPU 35a, a RAM 35b, a ROM 35c storing a program, an electrically rewritable EEPROM 35d, and an interface 35e. The power rectified by the rectifier circuit 33 is supplied to the demodulation circuit 34, the internal processing circuit 35, and the transmission modulation circuit 36.
[0014]
The output of the transmission modulation circuit 36 and the output of the interface 35e 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 point 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 to be a power consumption amount substantially equal to the transmission power consumed for transmitting data at the maximum communication distance (or communication limit distance) with the interrogator 10.
[0015]
The oscillation circuit 11 generates a reference signal of 4 MHz, for example. This reference signal is supplied to the first and second frequency dividers 12 and 13, and the signal (125 KHz) divided by 1/32 by the first frequency divider 12 and 1 by the second frequency divider 13. A signal divided by / 34 (117.6470588 KHz) is obtained.
When the internal processing circuit 19 instructs transmission of data having a logical value “1”, the selection circuit 15 selects the output of the first frequency dividing circuit 12, and a 125 kHz signal is output via the output amplifier 16 to the antenna coil 17. Send to. On the other hand, when the internal processing circuit 19 instructs the transmission of the data of the logical value “0”, the selection circuit 15 selects the output of the second frequency dividing circuit 13 and sends a signal of 117.6470588 KHz through the output amplifier 16. To the antenna coil 17.
[0016]
After the data transmission, the output of the first frequency divider 12 is selected by the selection circuit 15 for power transmission to the responder, and a 125 KHz signal is continuously sent to the antenna coil 17 via the output amplifier 16.
The tuning frequency of the tuning circuit composed of the transmission / reception coil 31 and the tuning capacitor 32 of the responder 30 is set to the center of two frequencies of 125 KHz and 117.76470588 KHz, that is, root (125 KHz × 1177.6470588) = 121.2678125 KHz. ing. Accordingly, the transponder 30 can receive signals having substantially the same strength when receiving the logical value “1” and when receiving the logical value “0”.
[0017]
When data is transmitted from the responder 30 to the interrogator 10, data generated by the CPU in the internal processing circuit 35 is transmitted to the modulation circuit 36 via the interface 35e, and is transmitted according to the output of the modulation circuit. The load circuit 37 turns on / off the switching transistor 39. Then, the current flowing through the transmission / reception coil 31 changes, and the strength of electromagnetic coupling between the transmission / reception coil 31 and the antenna coil 17 changes. The demodulator circuit 20 of the interrogator 10 detects a change in 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 circuit 14, and Demodulate the data. In practice, a band-pass filter performs a demodulation operation by detecting changes in the subband amplitude and phase of the 125 kHz signal output from the first frequency divider circuit 14.
[0018]
The internal processing circuit 35 connects a load circuit to the rectifier circuit when the power consumption in the internal processing circuit 35 is small, and outputs a control signal to be disconnected when the power consumption in the internal processing circuit is large through the interface 35e. . When the power consumption is large, an operation such as data writing to the electrically rewritable EEPROM 35d and a data transmission operation are raised.
[0019]
When the power consumption in 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, so that part of the current flowing through the tuning circuit is heated by the load circuit 37. As a result, 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 amount of power consumption, a control signal for turning off the switching transistor 39 is output via the interface 35e. However, since 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 is output from the modulation circuit 36. ON / OFF operation according to the signal.
[0020]
At this time, the resistance value of the load circuit 37 is set to be a power consumption amount substantially equal to the transmission power consumed for transmitting data at the maximum communication distance (or communication limit distance) with the interrogator 10. Therefore, 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.
Since the present invention is based on the assumption that the distance between the interrogator 10 and the responder 30 is close to the communication limit, when the distance between the interrogator 10 and the responder 30 becomes closer, the internal processing circuit 35 will When the power consumption of the load circuit 37 is small, the output increase of the rectifier circuit 33 cannot be suppressed only by the power consumption of the load circuit 37. This is because the resistance value of the load circuit 37 is set so that the power consumption is almost equal to the transmission power consumed for transmitting data at the maximum communication distance (or communication limit distance) with the interrogator 10. This is because the load when the distance between the interrogator 10 and the responder 30 becomes a close distance is too small.
[0021]
In order to prevent this situation, as a modification of the present embodiment, as shown in FIG. 2, a voltage detection means 41 for detecting the output voltage of the rectifier circuit 33, and a threshold value for which the voltage detection means 41 is set in advance. A load circuit 43 connected to the tuning circuit via a switching transistor 42 when a voltage exceeding the voltage is detected is provided. A current bypass is formed when the distance between the interrogator 10 and the responder 30 becomes a close distance by the load circuit 42, and a part (in some cases, most) of the current generated in the tuning circuit is heated by the load circuit 42. And the current to the rectifier circuit 33 is limited.
[0022]
Therefore, within the limit response distance, stable operation is possible regardless of the distance between the interrogator 10 and the responder 30.
[0023]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a data carrier that can secure sufficient transmission power when the responder 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]
DESCRIPTION OF SYMBOLS 10 Interrogator 11 Oscillator 12 Divider 13 Divider 15 Selector 17 Antenna coil 18 Tuning capacitor 19 Internal processing circuit 20 Demodulator 30 Response machine 31 Transceiver coil 32 Tuning capacitor 33 Rectifier 35 Internal processing circuit 37 Load for transmission Circuit 38 OR circuit

Claims (3)

A transmission / reception coil, a tuning capacitor connected thereto, a rectifier circuit for rectifying a signal received by the transmission / reception coil, an internal processing circuit driven by output power of the rectification circuit, and a transmission signal to the transmission / reception coil In a data carrier that includes a transmission circuit and performs signal processing according to instructions from an interrogator,
A load circuit for the rectifier circuit having a power consumption substantially equal to a transmission power consumed for transmitting data at the maximum communication distance with the interrogator;
A data carrier comprising 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. 3. The load circuit according to claim 2, wherein the load circuit is shared with a transmission load circuit for applying amplitude modulation to a voltage at both ends of the transmission / reception coil in order to transmit data from a data carrier toward the interrogator. Characteristic data carrier. A transmission / reception coil, a tuning capacitor connected thereto, a rectifier circuit connected to both ends of the transmission / reception coil and rectifying a signal received by the transmission / reception coil; an internal processing circuit driven by output power of the rectification circuit; In a data carrier comprising a transmission circuit for supplying a signal to the transmission / reception coil, and performing signal processing according to an instruction from an interrogator,
A load circuit for the rectifier circuit having a power consumption substantially equal to a transmission power consumed for transmitting data at the maximum communication distance with the interrogator;
A load control means for generating a load control signal for connecting the load circuit to the rectifier circuit when the power consumption in the internal processing circuit is small, and for disconnecting when the power consumption in the internal processing circuit is large;
Logic means for generating a logical sum signal of the output of the transmission circuit and a load control signal;
A data carrier comprising switching means for connecting the load circuit to the rectifier circuit according to the output of the logic means.

Images