JPH10303790A - Data carrier system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To automatically match impedance between a coiled antenna attached to an interrogator and a transmission circuit of a high-frequency carrier. The interrogator has a control unit for controlling the interrogator, a monitor unit for monitoring the intensity of the power transmitted from an antenna of the interrogator, and a transmission unit for transmitting data to the antenna. The configuration includes a matching circuit 14 for performing impedance matching with a circuit, and conversion tables 18 and 19 for indicating a plurality of capacitors provided in the matching circuit as continuous combined capacitance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data carrier system, and more particularly to a power supply method in an interrogator (antenna and controller) for supplying power to a transponder (data carrier) having no built-in power supply.

[0002]

2. Description of the Related Art A data carrier system known as an RF-ID system in Europe and the United States is composed of a transponder attached to a mobile body and a fixed interrogator, and uses radio between the transponder and the interrogator. It performs non-contact data communication, and its application is wide-ranging, such as transportation, logistics, security, and leisure.

The transponder of the data carrier system is:
Depending on the intended use, the shape (card type, cylinder type, box type, button type), the amount of stored information (about 1 to several hundred kilobytes), power supply type (built-in battery type, external supply type), etc. Selected. In particular, regarding the power supply method, the external supply type is easier to handle than the battery built-in type in terms of maintenance, such as the shape and cost of the transponder, the life of the built-in battery, and the replacement method.

In the external supply type, as an example, a high-frequency carrier is transmitted to a space from a coil-shaped antenna attached to an interrogator, and the power is extracted by electromagnetic induction in a coil-shaped receiving antenna of a transponder. Can be. Further, the transmission distance between the interrogator and the responder can be made remote by increasing the power supplied from the interrogator.

On the other hand, as an antenna attached to the interrogator, a so-called minute loop antenna, which is sufficiently shorter than the wavelength of a high-frequency carrier used for power supply, is sometimes used due to restrictions on the shape of the interrogator. Many.

[0006]

According to the above-mentioned prior art, it is necessary to supply a large amount of power in order to make the transmission distance between the interrogator and the transponder remote, and the coil attached to the interrogator is required. Since the length of the antenna is sufficiently shorter than the wavelength of the high-frequency carrier used for power supply, power cannot be transmitted efficiently unless the impedance of the antenna and the impedance of the transmission circuit are matched. was there.

An object of the present invention has been made in view of the above-mentioned problems, and has as its object to provide a matching method for obtaining optimum impedance matching for efficiently supplying power.

[0008]

In order to achieve the above object, a data carrier system according to the present invention transmits a high-frequency carrier to supply power from an interrogator to a transponder, and transmits the high-frequency carrier to the transponder and the interrogator. In a data carrier system for transmitting and receiving data between, the interrogator, a control unit for controlling the interrogator, and a monitor unit for monitoring the intensity of the power transmitted from the antenna of the interrogator A matching circuit for performing impedance matching between the antenna and the transmission circuit, and a conversion table for indicating a plurality of capacitors installed in the matching circuit as a continuous combined capacitance. is there.

Further, the conversion table has conversion information for outputting the combined capacitance of a series of circuits in which a plurality of capacitors are arranged as a combined capacitance in response to a continuous instruction from the control unit. .

Further, the intensity of the power transmitted from the antenna of the interrogator is monitored by a monitor, and the combined capacitance of the capacitors of the matching circuit is adjusted based on the intensity of the power to match the maximum power. This is a configuration to make it.

[0011]

FIG. 1 is a system configuration diagram of a data carrier system according to an embodiment of the present invention. The data carrier system includes an interrogator 1 and a responder 2. Generally, an interrogator often transmits data to a transponder by superimposing data on a carrier for power transmission, and this will be described as an example.

First, the transponder 2 attached to a moving body will be described. The transponder 2 resonates the carrier wave transmitted from the interrogator 1 to the frequency of the carrier wave by the transponder side coil 21 and the resonance capacitor 22 and efficiently receives the carrier wave. The voltage circuit 24 stabilizes the power supply voltage used inside the transponder and sends it out to each circuit element.

The transponder coil 21 also receives the data transmitted from the interrogator 1, generates a clock and demodulates the data in the receiving circuit 25, and transmits the received data to the control unit 20.
Send to The control unit 20 receives this and interprets the content, for example, modulates an “ID code” or the like stored in advance in the storage unit 27 by the transmission circuit 26, and To the interrogator 1.

According to a series of these operations, the transponder 2 receives the carrier transmitted from the interrogator 1 and operates to enable data transmission and reception. Therefore, transponder 2
It is indispensable that the carrier wave from the interrogator 1 reaches the transponder 2 in order to operate.

Next, the interrogator 1 which is fixed and used will be described. The interrogator 1 generates a frequency serving as a carrier wave in the oscillation circuit 11, modulates and amplifies the frequency in the transmission circuit 12 based on the transmission data from the interrogator-side control unit 10, and amplifies this through the matching circuit 14. Transmitted from the coil 15. When receiving data, the data is received and demodulated by the receiving circuit 13 via the interrogator-side coil 15 and is demodulated.
Send to The monitor unit 100 resonates the carrier transmitted from the interrogator side coil 15 to the frequency of the carrier by the monitoring coil 101 and the resonance capacitor 102, receives the carrier efficiently, and performs rectification and smoothing by the rectifying and smoothing circuit 103. , An A / D conversion circuit 104 converts the analog value into a digital value and sends it to the interrogator-side control unit 10. The interrogator-side control unit 10 uses this value for matching of the matching circuit 14. The control unit 10 has a storage unit 16 for storing transmission data, reception data, and the like. The power supply unit 17 is provided to supply a stable power supply to each circuit element inside the interrogator 1.

The monitoring coil 101 or the monitoring unit 100 including the monitoring coil 101
In the embodiment, the monitoring coil 101 is disposed between the interrogator side coil 15 and the responder side coil 21 at the time of monitoring, and the monitoring coil 101 is set at the normal interrogator side coil 15 except at the time of monitoring.
The structure may be such that it can be moved to a range that does not hinder the communication between the coil and the responder side coil 21.

Referring to FIG. 2, the configuration of the matching circuit 14 will be described. The matching circuit 14 includes capacitor circuits 1401 to 140
2 and a driving circuit 141 to 14 for switching the combined capacitance of the capacitor circuit.
2 and conversion tables 18 to 19 for continuously outputting the combined capacitance of the capacitor circuits 1401 to 1402 in response to a continuous instruction from the interrogator-side control unit 10. The conversion table will be described in detail later. However, in response to continuous instructions from ports PA0 to 5 (6 bits) and ports PB0 to 5 (6 bits) of the interrogator control unit 10, the capacitor circuits 1401 to 1402 4 is an address conversion table for continuously changing the combined capacitance of a plurality of capacitors disposed inside the table.

Referring to FIG. 3, the driving circuit 14 of the matching circuit 14
1 to 142 and the capacitor circuits 1401 to 1402 will be described. In FIG. 3, the drive circuit 142 and the capacitor circuit 140
The internal circuit No. 2 is omitted for convenience of notation. The matching circuit 140 includes capacitor circuits 1401 to 1402
And capacitors C0 to C5 and relay RL0, respectively.
To RL5 are connected in parallel.

The contacts of the relays RL0 to RL5 are closed / opened with the on / off operation of the coils of the relays RL0 to RL5 of the drive circuits 141 to 142. Therefore, the capacitor connected by the contacts of the relays RL0 to RL5 can be observed as a combined capacitance between the terminal Ci and the terminal Co, and the combination is 2 6, that is, 64.
Exists. The instruction to switch the relays RL0 to RL5 is sent from the conversion table corresponding to each, and received by the inversion buffers IC0 to IC5, and the diodes D0 to D0 are received.
5 is transmitted to the coils of the relays RL0 to RL5 connected in parallel.

In this embodiment, the capacitor circuit is switched by the relay circuit. However, the present invention is not particularly limited to this.

Referring to FIG. 4, the matching circuit 140 of the matching circuit 14 will be described. Generally, a circuit as shown in FIG. 3 is widely known as a matching circuit. FIG.
4A is a circuit effective when Zo> Za, FIG. 4B is an effective circuit when Zo <Za, and FIG. 4C is an effective circuit when Zo <Za <2Zo. In this embodiment, the matching circuit 140a shown in FIG. 4A is used as an example, but the present invention is not limited to this. It goes without saying that the matching circuit 140a may be selected in accordance with the impedance of the antenna serving as the load of the matching circuit. .

The conversion tables 18 to 19 of the matching circuit 14 will be described with reference to FIGS. In this embodiment, the capacitors C0 to C0 of the capacitor circuits 1401 to 1402 described above are used.
For the sake of explanation, six series (from 1 to 10 divided into 6 equal parts by 2 significant digits) are used as the basis, and the integer ratio division is performed. Adjusted in consideration of the above). Here, 1.0 (pF), 1.5 (pF), 2.2 (pF), 3.3
(pF), 4.7 (pF), and 6.8 (pF).
This is expressed as C0 = 1.0 (pF), C1 = 1.5 (pF), C
2 = 2.2 (pF), C3 = 3.3 (pF), C4 = 4.7
(pF) and C5 = 6.8 (pF). C5 is assigned to the most significant bit and C0 is assigned to the least significant bit.

In the table of FIG. 5, terms before conversion are addresses 0 to 63 in decimal notation (000000 in binary notation).
１１１111111) when the capacitor specified is selected. In other words, at address 1 in decimal notation, C0 is selected and the combined capacity is 1.0 (p
F), when address 2 is in decimal notation, C1 is selected and the combined capacitance is 1.5 (pF). When address 3 is in decimal notation, C0 and C1 are selected and the combined capacitance is 2. 5 (pF), from a minimum of 0 (pF) to a maximum of 19.5 (pF).
The range of F) can be specified.

However, in the table of FIG. 5, when the address of the term before the conversion continuously increases, the combined capacity of the term before the conversion and the combined capacity shown in FIG. It will be a discontinuous value. Thus, as shown in the graph of the converted address and the combined capacitance shown in FIG. 6B, the values shown in the converted terms are rearranged in order from the smallest value to the largest value, and the data column is replaced. It is.

That is, the port PA0 of the control unit 10
-5 (6 bits) and continuous instructions from ports PB0-5 (6 bits) are input as addresses, and the addresses are converted using this conversion table, and the drive circuits 141-142 are converted.
By operating the capacitor circuits 1401 to 1402 through the above, the combined capacitance value of the capacitor circuits can be continuously adjusted.

Although the conversion table in this embodiment is obtained from the values of the respective capacitors and the calculated values, if further accuracy is required, the combined capacity corresponding to the instruction of the control unit is actually obtained. Needless to say, it is good to make measurements based on the results.

The operation flow of the control of the matching circuit 14 by the interrogator-side control unit 10 will be described with reference to FIG. First, the capacitor circuit is initialized. For example, it is good to start with about half of the full value of the capacitor circuit (process 701). Then, the current value is measured by the monitor unit 100, and the measured value is stored as the initial value of the comparison data (steps 702 to 70).
3). The monitor current is measured by increasing the capacity of the capacitor circuit 1401 (C1a) (processing 704), and the result is compared with comparison data (processing 705).

If the current value increases, the current value is updated as comparison data (step 706), and further, steps 704 to 7
Repeat step 06. If it is determined in step 705 that the monitor current is not increasing, the process proceeds to step 707, in which the capacitance of the capacitor circuit 1401 (C1a) is reduced, the monitor current is measured (step 707), and the result is compared with comparison data. (Process 708).

If the current value has increased, the current value is updated as comparison data (step 709).
09 is repeated. If it is determined in step 708 that the monitor current is not increasing, the process proceeds to step 710, in which the capacity of the capacitor circuit 1402 (C2a) is increased and the monitor current is measured (step 710), and the result is compared with comparison data. (Process 711).

If the current value has increased, the current value is updated as comparison data (step 712).
Repeat step 12. If it is determined in step 711 that the monitor current is not increasing, the process proceeds to step 713, the monitor current is measured by reducing the capacity of the capacitor circuit 1402 (C2a) (step 713), and the result is compared with the comparison data. (Process 714).

If the current value has increased, the current value is updated as comparison data (step 715).
Repeat step 15. If it is determined in the above process 714 that the monitor current does not increase, the process proceeds to a process 716, and if it is the first time, the value is stored as the initial value of the maximum value data (process 7).
16 to process 717), and the process proceeds to process 704 to repeat a series of operations up to now. If it is not the first time in the process 716, the process proceeds to a process 718, where the process is compared with the previous maximum value data, and if the result is larger, the maximum value data is updated (processes 718 to 719).

If it is determined in step 718 that the comparison with the previous maximum value data is not large, the process proceeds to step 720, and it is determined whether or not the data is the same as the previous maximum value data (process 720). . Finally, if the comparison with the previous maximum value data is the same in the above process 720, it is determined that the maximum value has already been reached, that is, the matching has been achieved, and the process ends.

By the above operation, the optimum matching can be obtained by adjusting the values of the capacitor circuits 1401 to 1402 of the matching unit 14. Further, according to the present embodiment, it goes without saying that the power to the transponder can be controlled by designating an arbitrary control value from the control unit to the matching unit without depending on the information from the monitor unit.

[0034]

According to the present invention, the intensity of the electric power transmitted from the coiled antenna attached to the interrogator can be monitored by the monitor provided in the interrogator. The control unit can adjust the capacitance of the capacitor in the matching circuit to match the point where the maximum power can be obtained.In other words, the control unit automatically adjusts to variations in antenna manufacturing, aging, and changes in humidity and temperature. And it is possible to obtain an optimum matching.

In addition, even if it is a so-called minute loop antenna, the length of the coiled antenna attached to the interrogator is sufficiently shorter than the wavelength of the high-frequency carrier used for power supply. There is an effect that transmission can be performed efficiently by matching with the impedance of.

[Brief description of the drawings]

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

FIG. 2 is a matching circuit diagram of the data carrier system according to one embodiment of the present invention.

FIG. 3 is a diagram showing a drive circuit and a capacitor circuit of the data carrier system according to one embodiment of the present invention.

FIG. 4 is a diagram showing a matching circuit of the data carrier system according to the embodiment of the present invention.

FIG. 5 is a diagram showing a conversion table of the data carrier system according to one embodiment of the present invention.

FIG. 6 is a graph illustrating a capacity value of the data carrier system according to the embodiment of the present invention.

FIG. 7 is an operation flowchart of the data carrier system according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Data carrier system (interrogator), 2 ... Data carrier system (responder), 10 ... Interrogator side control part, 1
DESCRIPTION OF SYMBOLS 1 ... Oscillation circuit, 12 ... Transmission circuit, 13 ... Receiving circuit, 14
... matching circuit, 15 ... interrogator side coil, 16 ... storage unit, 1
7: power supply unit, 18, 19: conversion table, 20: responder side control unit, 21: responder side coil, 22: resonance capacitor, 23: rectifying and smoothing circuit, 24: constant voltage circuit, 25: receiving circuit, 26 ... transmitting circuit, 27 ... memory unit, 100 ... monitor unit, 101 ... monitoring coil, 102 ... resonant capacitor, 103 ... rectifying and smoothing circuit, 104 ... A / D conversion circuit,
140, 140a, 140b, 140c ... matching circuit, 141, 142 ... drive circuit, 1401, 1402 ...
Capacitor circuit, 701 to 721 ... processing, IC0 to IC5
... Reversal buffer, RL0-RL5 ... Relay, D0-D5
... Diodes, C0 to C5, C1a, C2a, C1b,
C2b, C1c, C2c: condenser, L1c: coil.

Claims (3)

[Claims] 1. A data carrier system for transmitting a high-frequency carrier to supply power from an interrogator to a transponder and transmitting and receiving data between the transponder and the interrogator. Control means for controlling the transmitter, monitoring means for monitoring the intensity of the power transmitted from the antenna of the interrogator, matching means for performing impedance matching between the antenna and the transmission circuit, A conversion table means for indicating a plurality of capacitors arranged in the matching means as a continuous combined capacitance. 2. The interrogator according to claim 1, wherein the conversion table means outputs conversion information for outputting a combined capacitance of a series of circuits in which a plurality of capacitors are arranged in response to a continuous instruction from the control means. 2. The data carrier system according to claim 1, wherein the conversion table has a conversion table. 3. In the interrogator, the intensity of the power transmitted from the antenna of the interrogator is monitored by monitoring means, and based on the intensity of the power, the combined capacitance of the capacitors of the matching means is adjusted to increase or decrease the power. 2. The data carrier system according to claim 1, further comprising matching means for matching the maximum point.