JPH1188241A - Data carrier system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply sufficient power for the transmission from a responder to an interrogator even when the responder and the interrogator are located comparatively away from each other. SOLUTION: An interrogator 10 gives a carrier with 1st or 2nd frequency different from each other depending on transmission data selectively to an antenna coil 17. A tuning frequency of a tuning circuit consisting of a transmission reception coil 31 and a tuning capacitor 32 of a responder 30 is selected to be a 3rd frequency that is an intermediate frequency between the 1st frequency and the 2nd frequency. The interrogator 10 sends a carrier with a frequency nearly equal to the 3rd frequency for a prescribed period after data transmission to the responder 30. In the case that the responder 30 conducts a prescribed requiring high power consumption, since the carrier with a frequency nearly equal to the tuning frequency is sent, the degree of coupling is enhanced and the responder 30 produces much more power.

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 system 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.

By the way, the power used in the transponder is generated by rectifying a signal received from the interrogator by a rectifier circuit.
Since this power is supplied during the period in which the carrier exists, the carrier is subjected to frequency modulation (FSK modulation) in which the carrier is always sent in order to continuously send the signal, and is transmitted. In the transponder, in order to increase the transmission efficiency of the carrier, a tuning capacitor is connected in parallel to the antenna coil to form a tuning circuit, and the tuning frequency of this tuning circuit is set to the center frequency of the two frequencies of the FSK-modulated carrier. You have set.

[0005]

Since the tuning frequency of the tuning circuit is set to the center frequency of the two frequencies of the carrier, the power transmission efficiency is high. The power consumption of the transponder varies greatly depending on the type of internal processing.
There is not much power consumption in the standby state where the command from the interrogator is received. On the other hand, when the EEPROM is used as the internal memory, the EEPROM is used.
Large power is consumed to drive a charge pump circuit for generating a high voltage when rewriting M.
Further, when data is transmitted from the transponder to the interrogator, the power consumption is several times that of the reception.

In the conventional data carrier system, when the distance between the transponder and the interrogator is close to the response limit distance, power is insufficient when the transponder receives an instruction from the interrogator and tries to return data to the interrogator. There was a problem that transmission could not be performed without it. The present invention solves the conventional problem and provides a data carrier system and an interrogator that can supply sufficient power for transmission from the transponder to the interrogator even when the distance between the transponder and the interrogator is relatively long. Aim.

[0007]

To solve the above problems, a data carrier system according to the present invention comprises a transmitting coil,
An interrogator having a transmission circuit that switches and supplies a carrier wave having first and second different frequencies to the transmission coil in accordance with transmission data, a transmission / reception coil, and a tuning capacitor connected thereto. A tuning circuit, a rectifying circuit for rectifying a signal received by the transmitting / receiving coil, and a signal processing circuit driven by output power of the rectifying circuit, performing signal processing according to an instruction from the interrogator, and supplying a transmitting signal to the transmitting / receiving coil. In a data carrier system comprising a transponder having a transponder, a tuning frequency of a tuning circuit of the transponder is first,
A third frequency intermediate to the second frequency,
The interrogator transmits a carrier wave of the third frequency after data transmission when instructing the power-consuming processing in the transponder.

According to another aspect of the present invention, there is provided an interrogator for a data carrier system, comprising: a transmission coil; first and second carriers having different frequencies;
A carrier generating means for generating a third carrier having an intermediate frequency between the carrier and a carrier of the first and second two frequencies in accordance with the logical value of the transmission data and supplying the carrier to the transmission coil and transmitting There is provided switching means for supplying the third carrier to the transmission coil during a predetermined period after transmitting the data.

According to another aspect of the present invention, there is provided a data carrier system comprising: a transmission coil; and a transmission coil for selectively supplying a carrier having first and second different frequencies to the transmission coil in accordance with transmission data. An interrogator having a circuit, a tuning circuit composed of a transmitting / receiving coil and a tuning capacitor connected thereto, a rectifying circuit for rectifying a signal received by the transmitting / receiving coil, and an interrogator driven by output power of the rectifying circuit. And a transponder having a signal processing circuit that performs signal processing in accordance with instructions from and supplies a transmission signal to a transmission / reception coil.
The tuning frequency of the tuning circuit of the transponder is set to a third frequency intermediate between the first and second frequencies, and the interrogator transmits the third frequency during a predetermined period after data transmission to the transponder. Is transmitted at a frequency substantially equal to.

As described above, in the system of the present invention, when the transponder performs internal signal processing, particularly when performing a process that consumes a large amount of power, a carrier wave substantially equal to the tuning frequency is transmitted to the transponder, thereby increasing the degree of coupling. , More power can be generated by the transponder.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an interrogator 10 and a transponder 30 of a data carrier system according to an embodiment of the present invention. In the figure, an interrogator 10 generates an oscillation circuit 11 for generating a basic signal of a carrier wave, and first, second and third carrier waves by dividing the basic signal from the oscillation circuit 11 by different frequency division ratios. Frequency divider circuits 12, 13, 14 and a selection circuit 15 for selecting and outputting one carrier wave from the first, second, and third carrier waves, an output amplifier 16, an antenna coil 1
7 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,
Rectifier circuit 33, demodulation circuit 34 for performing FSK demodulation, internal processing circuit 35, modulation circuit 36, and transmission load circuit 37
Having. Like the general signal processing circuit, the internal processing circuit 35 includes a CPU 35a, a RAM 35b, a ROM 35c storing programs and the like, an electrically rewritable EEPROM.
A ROM 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 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 reference signal is the third frequency divider 1
4 and divided by 1/33 (121.12
12121 KHz).

When the internal processing circuit 19 instructs the transmission of the data of the logical value "1", the output of the first frequency dividing circuit 12 is selected by the selecting circuit 15 and the signal of 125 KHz is output through the output amplifier 16. Send to antenna coil 17. 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.

The tuning frequency of the tuning circuit composed of the transmitting / receiving coil 31 and the tuning capacitor 32 of the transponder 30 is 1
The center of two frequencies of 25 KHz and 117.670588 KHz, that is, a root (125 KHz × 117.64)
70588) = 121.2678125 KHz. 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 interrogator 10 switches the selection circuit 15 during a period in which data is not transmitted to the transponder 30, and outputs the output 121.11212K of the third frequency dividing circuit 14.
Hz signal is continuously sent to the antenna coil 17. This frequency is substantially equal to the tuning frequency of the tuning circuit of the transponder 30. Therefore, the power received by the transponder 30 during this period (reception waiting period) is the period during which the interrogator 10 is transmitting data having the logical value “1” or “0” (data transmission period).
It is larger than. Therefore, even when the distance between the interrogator 10 and the responder 30 is closer to the communication limit,
The transponder 30 can perform operations that consume a large amount of power, such as rewriting the EEPROM in the internal processing circuit 35 and transmitting data to the interrogator 10.

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 to turn on / off the transistor of the transmission load circuit 37 according to the output of the modulation circuit. Then, the current flowing through the transmitting / receiving coil 31 changes, and the transmitting / receiving coil 3
1 and the strength of the electromagnetic coupling between the antenna coil 17 change. 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 signal of 121.112212 KHz output from the third frequency divider 14, and Demodulate the data from. In fact, the third frequency dividing circuit 1 is a bandpass filter.
The demodulation operation is performed by detecting a change in the sub-band amplitude of the signal of 121.112212 KHz output from No. 4.

As described above, in the data carrier system according to the embodiment of the present invention, even when the distance between the interrogator 10 and the transponder 30 is closer to the communication limit, the transponder 30 rewrites the EEPROM in the internal processing circuit 35. And interrogator 1
An operation of consuming a large amount of power, such as data transmission to 0, can be performed. Conventionally, the ID assigned to the transponder 30 assuming that the transponder 30 near the communication limit is within the communication limit is
This is a problem when the correct data is not sent back because the operation that consumes a large amount of power cannot be performed despite the return. When one interrogator 10 corresponds to a plurality of transponders 30 and there is at least one such transponder which is unstable, a system for repeating data transmission requests to this transponder 30 many times is provided. According to the present invention, if the data from the interrogator 10 is within the distance that the transponder 30 can receive the data, the transponder 30 has sufficient power to perform internal processing. Is always obtained, so that the above problem does not occur.

In the above embodiment, the interrogator 10
During a period in which data is not transmitted to the transponder 30, the selection circuit 15 is switched to output the signal of 121.112212 KHz of the third frequency dividing circuit 14 to the antenna coil 1.
7, the output of the third frequency dividing circuit 14 is transmitted only when a command for causing the transponder 30 to perform an operation with large power consumption is transmitted. In other cases, the output of the first frequency dividing circuit 14 is transmitted. The output of the frequency dividing circuit 12 or the second frequency dividing circuit 13 may be transmitted.

[0020]

As described above, according to the present invention, even when the distance between the transponder and the interrogator is relatively long, the data carrier system and the interrogator can supply sufficient power for transmission from the transponder to the interrogator. Can be provided.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Interrogator 11 Oscillation circuit 12 Divider circuit 13 Divider circuit 14 Divider circuit 15 Selection circuit 17 Antenna coil 18 Tuning capacitor 19 Internal processing circuit 20 Demodulation circuit 30 Transponder 31 Transmitter / receiver coil 32 Tuning capacitor 33 Rectifier circuit 35 Internal processing circuit 37 Transmission load circuit

Claims (5)

[Claims] 1. An interrogator having a transmission coil and a transmission circuit for switching and supplying a carrier wave having first and second different frequencies to the transmission coil in accordance with transmission data; And a rectifying circuit configured to rectify a signal received by the transmitting and receiving coil. The rectifying circuit is driven by output power of the rectifying circuit, performs signal processing according to an instruction from the interrogator, and transmits the signal. And a transponder having a signal processing circuit for supplying a signal to the transmission / reception coil, wherein a tuning frequency of the tuning circuit of the transponder is a third frequency intermediate between the first and second frequencies. The interrogator transmits the carrier of the third frequency after transmitting data when instructing the power-consuming process in the transponder. Data carrier system according to claim. 2. A transmission coil, carrier generation means for generating first and second carriers having different frequencies and a third carrier having an intermediate frequency between the first and second carriers, and transmission data. Switching the carrier waves of the first and second two frequencies according to a logical value and supplying the carrier waves to the transmission coil, and supplying the third carrier wave to the transmission coil during a predetermined period after transmitting the transmission data. An interrogator for a data carrier system having switching means. 3. An interrogator having a transmission coil, and a transmission circuit for switching and supplying a carrier having first and second different frequencies to the transmission coil in accordance with transmission data; and a transmission / reception coil and connection thereto. A tuning circuit composed of a tuning capacitor, a rectifier circuit for rectifying a signal received by the transmitting and receiving coil, and driven by output power of the rectifier circuit, performing signal processing according to an instruction from the interrogator and transmitting the signal. And a transponder having a signal processing circuit for supplying a signal to the transmission / reception coil, wherein a tuning frequency of the tuning circuit of the transponder is a third frequency intermediate between the first and second frequencies. The interrogator transmits a carrier having a frequency substantially equal to the third frequency during a predetermined period after data transmission to the transponder. And data carrier system. 4. The transponder according to claim 1, further comprising an electrically rewritable non-volatile memory, wherein the interrogator rewrites at least the transponder with data to the electrically rewritable non-volatile memory. And transmitting a carrier having a frequency substantially equal to the third frequency for a predetermined period after the instruction is issued. 5. The data carrier according to claim 1, wherein the interrogator transmits a carrier having a frequency substantially equal to the third frequency during at least a predetermined period after instructing the transponder to transmit data. system.