JP2002334310A - Non-contact IC card and method of adjusting antenna resonance circuit thereof - Google Patents

Abstract

(57) Abstract: A method for adjusting an antenna resonance circuit for optimizing a reception state of a non-contact IC card and a non-contact IC card using the same are provided. An electromagnetic wave is received by an antenna resonance circuit,
An induced voltage is generated internally by the rectifier circuit 22, and the induced voltage is detected by the reception level detection 25, and at the same time, the reception data and frame error rate (FER) are detected by the modulation / demodulation circuit 24.
Is detected, and the quality factor and the resonance frequency are automatically adjusted by varying the resistance and the capacitor of the antenna resonance circuit 21 according to the detected reception level and the value of the FER.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contactless IC card using electromagnetic waves and a method for adjusting an antenna resonance circuit thereof.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a communication system using a contactless IC card. Generally, since the non-contact IC card 12 does not have a battery inside, the reader / writer 11 (hereinafter referred to as R /
Called W. ) Generates an internal voltage and demodulates the modulated wave by using the modulated electromagnetic wave, receives data transmitted from the R / W 11, and sends a non-contact IC to the R / W 11.
The load of the card 12 itself fluctuates and responds.

The non-contact IC card 12 forms an antenna resonance circuit with a coil L and a capacitor C corresponding to an antenna, and a pseudo transformer resonance between the R / W 11 and the non-contact IC card 12 causes the R / W 11 The transmission and reception have been performed by causing LC resonance near the transmitted electromagnetic wave frequency.

[0004] The non-contact IC card 12 is rarely used in a fixed manner because of its convenience. It is assumed that the non-contact IC card 12 is used in a ticket gate of a station. It is essential to be able to communicate even if it is placed in a pass case or the like and overlaps with another non-contact IC card 12. In this case, if the communication distance between the R / W 11 and the non-contact IC card 12 changes or overlaps with another non-contact IC card 12, the mutual conductance by the pseudo transformer resonance circuit or the non-contact IC card 12 side antenna resonance circuit It is conceivable that when the capacitor C changes, the resonance frequency shifts and communication becomes impossible.

To cope with such a problem, Japanese Patent Application Laid-Open No. 9-62816 or Japanese Patent Application Laid-Open
As disclosed in Japanese Patent Application No. 0-187916, the quality factor or the resonance frequency of the antenna resonance circuit of the non-contact IC card is to be varied according to the reception detection level.

[0006]

However, in the adjustment of the resonance frequency or the quality factor by the conventional method, for example, an excessive electromagnetic wave enters the non-contact IC card because the communication distance with the R / W 11 is too short. In this case, according to the conventional method, the reception level (voltage) is checked, and the resonance frequency or the quality factor is adjusted to lower the reception level. At this time, the control to control the IC chip in the non-contact IC card 12 to be lower than the absolute maximum rated voltage is, of course, stopped when the reception level (voltage) reaches a certain setting.

[0007] However, the reception level is not always good at the set reception level. because,
Even when radio wave interference occurs temporarily due to the communication environment, a communication error may occur even at a certain set level and normal reception may not be possible.

In addition, according to the conventional method, a plurality of non-contact IC cards are overlapped, and in consideration of a decrease in the resonance frequency due to an increase in the capacitance of the antenna resonance circuit due to the capacitive coupling between the cards, the R / W 11 is reduced when one IC card is used. The resonance frequency was set higher than the carrier frequency. This state is shown in FIG. For example, when the resonance frequency of one non-contact IC card 12 is set to be higher than the carrier frequency f ₀ of the R / W 11 and a plurality of non-contact IC cards 12 are overlapped, the antenna resonance is caused by capacitive coupling between the cards. As the capacitors in the circuit increase, the resonant frequency appears to fall below the R / W carrier frequency. According to the conventional method, it is determined as one non-contact IC card 12 and the reception level appears to be lowered. Therefore, there is a possibility that an operation of lowering the resonance frequency to approach the resonance frequency of the R / W 11 may be performed. In this case, lowering the resonance frequency further lowers the resonance frequency, which may make it impossible to perform communication at worst.

An object of the present invention is to solve the above-mentioned problems in the prior art and optimize the adjustment of the antenna resonance circuit.

[0010]

In order to achieve the above object, the present invention provides a detecting means for detecting a reception level from an antenna resonance circuit in a non-contact IC card 12 and supplying an output voltage corresponding to the reception level. The non-contact IC card 12 has a means for adjusting a resonance frequency and a quality factor of an antenna resonance circuit by a frame error rate (FER) indicating a reception data state.

[0011] Further, the selection of these adjustment methods has an adjustment algorithm based on the reception level and FER,
Further, the algorithm parameters can be set individually for the non-contact IC card 12 at the time of manufacturing the card.

[0012]

Embodiments of the present invention will be described below in detail. FIG. 1 shows the configuration of a contactless IC card system to which the present invention is applied. Further, the non-contact I according to the present invention
FIG. 2 shows the configuration of the C card 12.

The contactless IC card system shown in FIG.
Non-contact IC card 12, R / W 11 for supplying a modulated electromagnetic wave to non-contact IC card 12 to read and write the data section of non-contact IC card 12, and PC 10 for controlling the same
Consists of

The non-contact IC card 12 shown in FIG.
It comprises an antenna resonance circuit 21 for receiving the modulated electromagnetic wave output from W11, a rectification circuit 22 for rectifying the electromagnetic wave received from the antenna resonance circuit, and a regulator circuit 23 for maintaining the rectified voltage at a predetermined voltage. .

Further, a modulation / demodulation circuit 24 for modulating and demodulating the electromagnetic wave received by the antenna resonance circuit 21 and detecting whether or not there is an error in a reception data portion, and a reception level detection circuit 25 for detecting a voltage rectified from the rectification circuit 22. And comprises a CPU 26 and a memory 27 for controlling these.

FIG. 3 shows a resonance adjusting circuit 2 for adjusting the resonance frequency and the quality factor in the antenna resonance circuit 21.
8 is an example. The gates of the FETs 310 to 313 in the figure are connected to the I / O interface of the CPU 26.
When the CPU 26 is turned on / off through 0,331 through the FETs 310 and 311 and the quality factor is changed, the CPU 26 turns on / off the resistors R340 and 341 through the FETs 312 and 313.

As an operation of the non-contact IC card 12, R /
When receiving an electromagnetic wave from W11, a voltage is supplied to the inside through the antenna resonance circuit 21, the rectifier circuit 22, and the regulator circuit 23. If the voltage is equal to or higher than a predetermined voltage, the CPU 26 is reset and the non-contact IC card can be operated. At this time, the reception level is notified to the CPU 26 through the reception level detection circuit 25.

The R / W 11 sends out a periodically modulated electromagnetic wave and inquires whether a non-contact IC card 12 exists. Upon receiving the modulated electromagnetic wave from the antenna resonance circuit 21, the non-contact IC card 12 demodulates the modulated electromagnetic wave by the modulation / demodulation circuit 24 to determine whether the received data is normal. If the received data is normal, the received data is sent to the CPU 26. . If it is determined that the received data is abnormal, a reception error (FER
Error) to the CPU.

FIG. 4 shows an example of a data format sent from the R / W 11 to the non-contact IC card 12. This data format includes error detection such as a header section 410 consisting of a bit or byte string indicating the head of data such as a preamble and a unique word (UW), a data length section 411 indicating the length of the data section 412, a data section 412, and a CRC. Or, it is composed of a correction unit 413.

FIG. 5 shows an example of the demodulation processing of the modulation / demodulation circuit 24. In this example, the target of error detection or correction is the data section 4
Only 12 are assumed. First, in the header receiving unit 510,
The data format defined in FIG. 4 is detected, and when the header section 410 is detected, the reception
And the reception level is also notified to the CPU 26.
It is assumed that the reception level is always notified to the CPU 26 regardless of the presence or absence of the detection of the header section 410. Also,
The data received in the header section 410 is the next block 5
After performing data length recognition in step 11 and detecting the length of the data section 412, the header section 410 and data length section 411 of the data format are deleted in the next block 512, and error detection or correction is performed in the next block 513, Block 51
4, the error detection or correction unit 413 is deleted, and the data unit 4 is deleted.
Only 12 is sent to the CPU 26. If there is an error,
The error signal held in the flip-flop 515 is
Notify the CPU 26 as an error.

When the reception level, the reception data, and the FER error are notified to the CPU 26 as described above,
Reference numeral 26 controls the resonance adjustment circuit 28 by operating the resonance adjustment algorithm based on the information stored in the memory 27.

FIGS. 6, 7, and 8 show examples of the resonance adjustment algorithm.
Shown in 6, 7 and 8 show an algorithm for detecting the reception level and the FER and adjusting the quality factor (Q value) or the resonance frequency. The algorithm will be described below. The CPU 26 outputs a signal from the modulation / demodulation circuit 24.
At the same time that the detection of the header section 410 is notified, the reception level is detected (step 611).

Next, the CPU 26 refers to the reception level parameter set in the CPU memory 27 and determines whether the reception level is low, medium, or high (step 612).
If the reception level is medium, F
Check if there is an ER error (Step 6)
13) If there is no error, the receiver goes to the reception level again without doing anything. Here, if there is an FER error, it is usually improved by increasing the reception level. Therefore, control is performed when it is determined that the reception level is low in order to increase the reception level.

In the control for reducing the reception level, the resistors 340 and 341 shown in FIG. 3 are controlled to reduce the antenna resistance, thereby controlling to increase the quality factor (Q value) and increase the reception level ( Steps 615 and 616). Here, when the Q value reaches the maximum controllable value, it is detected that there is an FER error because the Q value cannot be increased (step 61).
7). If there is no FER error, the state is kept as it is, and the reception level is detected again. If there is an FER error, the type of algorithm 2 set as a parameter is determined (step 618). Since the default is algorithm 2-1, algorithm 2 in FIG.
1 is performed.

In the algorithm 2-1, first, the current reception level is obtained (step 810), and the resonance frequency is lowered by one step by controlling the capacitors 330 and 331 shown in FIG. 3 to increase the capacitor capacitance (step 810). 81
1). Here, since the antenna resonance frequency of the non-contact IC card 12 is set to be higher than the carrier frequency transmitted by the R / W 11 in the initial value,
By lowering the resonance frequency, the reception level is usually increased by approaching the R / W carrier frequency. For example, FIG.
When two capacitors can be controlled by the antenna resonance circuit 21, the resonance frequency can be controlled in four stages.

After lowering the resonance frequency by one step, the reception level is obtained again (step 812) and compared with the value before the reduction of the resonance frequency (step 813). Is larger, the current algorithm 2-1 is reset to the algorithm 2 (step 8).
14) The reception level is detected again. If the reception level becomes low despite setting the resonance frequency low, it is determined that the resonance frequency has already been lowered by the plurality of non-contact IC cards 12, and conversely, the resonance frequency is raised by one step. (Step 815), and the reception levels are compared (step 817). If the reception level has risen due to an increase in the resonance frequency, algorithm 2-2 is set as the algorithm 2 (step 818), and the reception level is detected again. If the reception level does not increase, the reception level is detected again.

In the control of the high reception level, contrary to the control of the low reception level, control is performed to lower the Q value to lower the reception level (steps 621 and 622). When the Q value reaches the minimum controllable value, it is detected that there is an FER error because the Q value cannot be reduced.
(Step 623). If there is no FER error, the state is kept as it is, and the reception level is detected again. FE
If there is an R error, the type of algorithm 1 set as a parameter is determined (step 62).
4). Since the default is Algorithm 1-1, the control of Algorithm 1-1 in FIG. 7 is performed. In the algorithm 1-1, first, the current reception level is obtained (step 710).
The resonance frequency is raised by one step by controlling the capacitor shown in FIG. 3 to reduce the capacitance (step 711). Since the antenna resonance frequency of the non-contact IC card 12 is set to be higher than the carrier frequency transmitted by the R / W 11 in the initial value, the resonance frequency is further increased to further move away from the R / W carrier frequency. Therefore, the reception level decreases.

After raising the resonance frequency by one step, the reception level is acquired again (step 712) and compared with the value before the resonance frequency was raised (step 713). Is smaller, the current algorithm 1-1 is reset to the algorithm 1 (step 7).
14) The reception level is detected again. If the reception level increases despite setting the resonance frequency high, it is determined that the resonance frequency has already been lowered by the plurality of non-contact IC cards 12, and conversely, the resonance frequency is lowered by one step. (Step 715), the reception level is acquired again (Step 716), and the reception level is compared with the reception level before the resonance frequency was lowered (Step 717). If the reception level has decreased due to the lowering of the resonance frequency, algorithm 1-2 is set as algorithm 1 (step 718), and the reception level is detected again. If the reception level has not dropped, the reception level is detected again.

The antenna resonance circuit adjustment processing flow according to the above example can constantly monitor the reception level, maintain a reception state without reception errors, and can cope with a case where there are a plurality of non-contact IC cards 12. Becomes

FIG. 9 shows an example of parameters used in the resonance adjustment algorithm. These parameters are stored in the memory 2 of the non-contact IC card 12 when the card is manufactured.
7 is written.

In the example of FIG. 9, there is a reception level setting area for defining the reception level, and the reception level small / medium / high defined in FIG. 6 can be set. In the example of FIG. 9, if the reception level is low, 2.5 V or less, the medium level is 2.5 to 5.5 V, and the high level is 5.5 V.
This is an example set as above.

There is also an area for setting the factory setting of the Q value and the resonance frequency, and the initial setting of the resistance and the capacitor of the antenna resonance circuit shown in FIG. Here, Q
An example of setting the value is three resistors, and eight types of 0 to 7 can be set. The work area is an area in which, when the Q value is changed during the resonance circuit adjustment processing flows in FIGS. 6 to 8, how much the Q value is changed from the initial setting value is stored. This work area is C
When the PU power supply is turned on and communication is completed, it is necessary to always clear the flag and set it to 0.

In the example of setting the resonance frequency, an example in which two capacitors are used is shown. In the adjustment algorithm setting area, FIG. 7 shows a case where the reception level is low or high in FIG. 6, the Q value becomes out of control, and a FER error occurs.
8 has a default area in which the initial settings of the algorithms 1 and 2 can be set, and a work area in which an algorithm different from the initial setting is set during the processing of the algorithm 1 or 2.

This work area is set when the CPU power is turned on.
At the end of communication, it must be cleared and set to the same as the initial setting. Non-contact IC
Algorithms 1-1 and 2-1 for one card 12 are set in advance.

The above description describes the control at the time of reception data. At the time of transmission, the modulated electromagnetic wave from the R / W 11 is demodulated, and the CPU analyzes the contents. Modulation and demodulation circuit 2
Through 4, the load is changed and modulated.

In the above description, it is assumed that there is received data. However, when there is no received data, it is possible to control only by the reception level. In this case, as shown in FIG. 5, the CPU 26 detects a reception signal transmitted from the demodulation unit of the modulation / demodulation circuit unit,
If the reception is known, the FER value is used. If the reception is not received, all the FERs are determined to be OK, and the processing can be performed.

[0037]

The present invention is different from the conventional control of the antenna resonance circuit based on the reception level.
By combining R, the antenna resonance circuit can be adjusted more accurately, and the communication environment with the R / W 11 can be set optimally.

Unlike the conventional method, the non-contact IC card 12 has an algorithm for monitoring the reception level by raising and lowering the resonance frequency and setting the optimum reception level.
Are not set erroneously even if a plurality of sheets are overlapped.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a non-contact IC card system.

FIG. 2 is a configuration diagram of a non-contact IC card of the present invention.

FIG. 3 is a resonance adjustment circuit diagram of the non-contact IC card of the present invention.

FIG. 4 is a diagram showing a received data format of the contactless IC card of the present invention.

FIG. 5 is a diagram showing a demodulation process of a modulation / demodulation circuit unit of the non-contact IC card of the present invention.

FIG. 6 is a flowchart of processing for adjusting an antenna resonance circuit of the non-contact IC card of the present invention.

FIG. 7 is a processing flow of a resonance adjustment algorithm 1 of the non-contact IC card of the present invention.

FIG. 8 is a processing flow of a resonance adjustment algorithm 2 of the non-contact IC card of the present invention.

FIG. 9 is a diagram showing antenna resonance circuit adjustment parameters of the memory in the non-contact IC card of the present invention.

FIG. 10 is a diagram showing the relationship between the frequency and the reception level of the contactless IC card of the present invention.

[Explanation of symbols]

 Reference Signs List 10 PC 11 R / W 12 Non-contact card IC 21 Antenna resonance circuit 22 Rectifier circuit 23 Regulator 24 Modulation / demodulation circuit 25 Reception level detection circuit 26 CPU 27 Memory 28 Resonance adjustment circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C005 MA22 NA08 5B035 BB09 CA11 CA23 CA33 5K012 AC08 AC10 AD01 AD05

Claims (4)

[Claims] An antenna resonance circuit adjusting method for a non-contact IC card for performing data communication and power supply by using an electromagnetic wave, wherein the electromagnetic wave is received by an antenna resonance circuit, and an induced voltage is internally generated by a rectifier circuit. At the same time as detecting the induced voltage by the reception level detection, the modulation and demodulation circuit detects the reception data and the frame error rate (hereinafter referred to as FER). An antenna resonance circuit adjustment method for automatically adjusting a quality factor and a resonance frequency by changing the variable. 2. The antenna resonance circuit adjustment according to claim 1, wherein the quality factor of the antenna resonance circuit is increased or decreased in accordance with the detected reception level, and the resonance frequency of the antenna resonance circuit is increased or decreased when there is an error in the received data. Method. 3. A non-contact IC card for performing data communication and power supply using electromagnetic waves, an antenna resonance circuit for receiving electromagnetic waves, a rectification circuit for rectifying the electromagnetic waves received by the antenna resonance circuit, and detecting a rectified voltage. Receiving level detection circuit, a regulator circuit for maintaining the rectified voltage at a predetermined potential, and a modulation / demodulation circuit for demodulating an electromagnetic wave received by the antenna resonance circuit and detecting received data and a frame error rate (hereinafter referred to as FER). A resonance adjustment circuit including a plurality of resistors and capacitors as means for varying the quality factor and the resonance frequency of the antenna resonance circuit; and varying the quality factor and the resonance frequency of the antenna resonance circuit according to the detected reception level and the value of the FER. Non-contact IC card having CPU and memory for controlling 4. The non-contact IC card according to claim 3, wherein the memory has an adjustment parameter area for an antenna resonance circuit, and a default value is set when the card is manufactured.