JP2004348661A - Non-contact ic card - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-contact IC card by which high level and low level are always exactly detected; the frequency of occurrence of communication errors is reduced; and stable communication is available. <P>SOLUTION: The non-contact IC card makes the hysteresis width of a comparator 16 vary in accordance with the level of an input signal to the comparator 16, in actuality, in accordance with the output voltage value of a full wave rectifying circuit 12 or a value of current passing through a shunt regulator 15. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is used, for example, as a personal authentication medium, a basic resident register card, a credit card, and the like in an entrance / exit management device, receives an electromagnetic wave transmitted from a non-contact type card reader / writer, and operates the operating voltage by the received electromagnetic wave. A battery-less non-contact type that performs data processing such as writing and reading data to and from a rewritable nonvolatile memory by performing wireless communication with a non-contact type card reader / writer by operating It relates to a type IC card (so-called wireless card).
[0002]
[Prior art]
Recently, for example, a non-contact type IC card called a so-called wireless card may be used as a personal authentication medium in the entrance / exit management device. In that case, a non-contact type IC card that records personal physical characteristics etc. is distributed to visitors and wirelessly communicates with a non-contact type card reader / writer installed at the entrance of the room The physical characteristic information is collated, and the opening and closing of the entrance door is controlled.
[0003]
The non-contact type IC card called a wireless card is mainly a battery-less type IC card due to elimination of battery replacement work, downsizing, cost reduction, and long life.
Therefore, recent non-contact type IC cards operate by receiving an electromagnetic wave transmitted from a non-contact type card reader / writer, generating an operating voltage using the received electromagnetic wave, and supplying the operating voltage to each unit as an operating power supply. It has become.
[0004]
By the way, the signal receiving section in this type of non-contact type IC card or a non-contact type card reader / writer for performing wireless communication with the non-contact type IC card is strongly affected by noise on the received signal, so that it is always used. An accurate output signal could not be obtained, and a response was required.
[0005]
Therefore, recently, as an answer to this, an envelope detection circuit for performing envelope detection on the received signal, a high-pass filter for removing a DC component from the signal after performing the envelope detection, It has a comparison circuit consisting of a Schmitt circuit that creates a digital output signal consisting of high level and low level for the signal from which the DC component has been removed by the high-pass filter, and performs envelope detection on the received signal using an envelope detection circuit. A DC component is removed by a filter, and a digital output signal that oscillates at a high level and a low level is accurately generated by comparing a detection signal that oscillates around the obtained ground potential with a comparison circuit including a Schmitt circuit. Some are known (for example, see Patent Document 1).
[0006]
[Patent Document 1]
JP 2002-368830 A
[Problems to be solved by the invention]
However, in the technique of Patent Document 1 described above, since the hysteresis width of the Schmitt circuit is an eigenvalue determined by the resistance value, the hysteresis width is not an appropriate value depending on the level of the received signal, and the high level and the low level cannot be detected accurately. There's a problem. This is a serious problem particularly when the magnetic field strength of the non-contact card reader / writer and the positional relationship between the non-contact card reader / writer and the antenna of the non-contact IC card are irregular.
[0008]
Therefore, the present invention makes it possible to always accurately detect the high level and the low level by changing the hysteresis width of the comparator according to the level of the received signal, reduce the frequency of communication errors, and enable stable communication. It is an object of the present invention to provide a non-contact type IC card.
[0009]
Further, the present invention provides an automatic gain control means on the input side of the comparator, and by fixing the hysteresis width of the comparator, can always accurately detect the high level and the low level, reduce the frequency of occurrence of communication errors, An object of the present invention is to provide a non-contact type IC card that enables stable communication.
[0010]
[Means for Solving the Problems]
The non-contact type IC card of the present invention receives an electromagnetic wave transmitted from an external device, generates an operating voltage based on the received electromagnetic wave, operates, and performs predetermined communication by performing wireless communication with the external device. In a non-contact type IC card for performing data processing and the like, an antenna unit for performing wireless communication with an external device, a rectifying unit for rectifying a reception signal obtained from an output of the antenna unit, and a rectifying unit. A power supply generating means for generating an operating voltage of the contactless IC card from the rectified reception signal, a comparator having a hysteresis characteristic for obtaining reception data by binarizing the reception signal rectified by the rectification means; And a hysteresis control means for changing a hysteresis width of the comparator according to the level of the received signal.
[0011]
Further, the non-contact type IC card of the present invention receives an electromagnetic wave transmitted from an external device, generates an operating voltage by using the received electromagnetic wave, operates, and performs wireless communication with the external device. In a non-contact type IC card for performing predetermined data processing or the like, an antenna unit for performing wireless communication with an external device, a rectifying unit for rectifying a reception signal obtained from an output of the antenna unit, Power supply generating means for generating an operating voltage of the contactless IC card from the received signal rectified by the means, and a hysteresis characteristic of obtaining received data by binarizing the received signal rectified by the rectifying means. A comparator and automatic gain control means provided on the input side of the comparator for controlling the input signal level to the comparator to be constant. It is Bei.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, a first embodiment will be described.
FIG. 1 schematically shows a main configuration of a non-contact type IC card according to the first embodiment. In FIG. 1, an antenna unit 11 is for performing wireless communication with a non-contact type IC card reader / writer (not shown), and includes an antenna coil and a tuning capacitor forming an LC resonance circuit therewith. ing. The reception signal obtained from the antenna unit 11 is sent to a full-wave rectification circuit 12 as rectification means, where it is rectified.
[0013]
At the output end of the full-wave rectification circuit 12, a smoothing circuit 13 for smoothing the output voltage of the full-wave rectification circuit 12, a voltage detection circuit 14 as a voltage detection means for detecting the output voltage of the full-wave rectification circuit 12, A shunt regulator (voltage stabilizing circuit) 15 as a power generating means for generating a DC voltage stabilized by an output voltage of the rectifying circuit 12 and supplying the DC voltage to each section as an operating voltage, and an output (rectified) of the full-wave rectifying circuit 12 Each of the comparators 16 has a hysteresis characteristic for obtaining received data by binarizing the received signal.
[0014]
The shunt regulator 15 is connected to a current detection circuit 17 as current detection means for detecting a current flowing from the shunt regulator 15. The detection result of the current detection circuit 17 is sent to the control unit 18 as a hysteresis control unit together with the detection result of the voltage detection circuit 14.
[0015]
The control unit 18 uses the voltage value detected by the voltage detection circuit 14, the current value detected by the current detection circuit 17, or both values as the level of the received signal. Is controlled so as to change the hysteresis width to the optimum value.
[0016]
The output (received data) of the comparator 16 is sent to the modulation / demodulation unit 19, where it is subjected to demodulation processing and then used for predetermined data processing (for example, arithmetic processing and writing / reading to / from a memory).
[0017]
Next, the operation of the main part in such a configuration will be described.
First, in order to clarify the operation and effect of the present invention, a case where the hysteresis width hys of the comparator 16 in the conventional method is fixed will be described with reference to FIG. As shown in FIG. 2A, when the level of the input signal to the comparator 16 is small, the signal that changes from the low level to the high level does not exceed Vl although there is variation, so that the signal changes from the low level to the high level without any problem. Has been valued. However, as shown in FIG. 2B, when the level of the input signal is large, the variation also becomes large. Therefore, the binarization from the low level to the high level is performed at the high level as shown at the point of interest P. The desired range becomes low level, and normal communication cannot be performed. Vref in the figure indicates a reference voltage for binarizing the input signal.
[0018]
Next, a case where the hysteresis width hys of the comparator 16 according to the present invention fluctuates according to the level of an input signal (received signal) will be described with reference to FIG. In this case, as shown in FIG. 3B, when the level of the input signal to the comparator 16 increases, the hysteresis width hys also increases accordingly, so that the binarization from the low level to the high level can be performed without any problem. Understand. FIG. 3A shows a case where the level of the input signal to the comparator 16 is low.
[0019]
Hereinafter, a method of changing the hysteresis width hys of the comparator 16 according to the level of the input signal will be specifically described.
The first method is to change the hysteresis width hys to an appropriate hysteresis width via the control unit 18 according to the voltage value detected by the voltage detection circuit 14 (the output voltage value of the full-wave rectification circuit 12). This method is particularly effective when the input signal level is low.
[0020]
In the second method, the current flowing from the shunt regulator 15 is detected by the current detection circuit 17 and the hysteresis width hys is changed to an appropriate hysteresis width hys via the control unit 18 according to the current value. This method is particularly effective when the level of the input signal is large.
[0021]
The third method uses both the first method and the second method. This method is effective regardless of the level of the input signal.
[0022]
The output of the comparator 16 may be in the case where the low level and the high level are opposite.
[0023]
As described above, the hysteresis width hys of the comparator 16 is changed in accordance with the output voltage value of the full-wave rectifier circuit 12 and the current value flowing out of the shunt regulator 15 according to the level of the input signal to the comparator 16. Accordingly, the high level and the low level can always be accurately detected, the frequency of occurrence of communication errors is reduced, and stable communication is possible.
[0024]
Next, a second embodiment will be described.
FIG. 4 schematically shows a main configuration of a non-contact type IC card according to the second embodiment. The difference of the second embodiment from the first embodiment is that an automatic gain control circuit (AGC) is provided on the input side of the comparator 16 as an automatic gain control means for controlling the input signal level to the comparator 16 to be constant. Circuit 20) and the voltage detection circuit 14, the current detection circuit 17 and the control unit 18 are omitted, and the other parts are the same as those of the first embodiment. I do.
[0025]
With this configuration, even if the level of the received signal is low as shown in FIG. 5A or the level of the received signal is high as shown in FIG. Since the level of the input signal is controlled to a constant level by the AGC circuit 20 as shown in FIG. 5C, it can be seen that the signal is binarized from a low level to a high level without any problem.
[0026]
As described above, by setting the AGC circuit 20 in the preceding stage of the comparator 16 and fixing the hysteresis width hys of the comparator 16, the high level and the low level can always be detected accurately, and the frequency of occurrence of communication errors can be reduced. Stable communication becomes possible.
[0027]
【The invention's effect】
As described in detail above, according to the present invention, by varying the hysteresis width of the comparator according to the level of the received signal, the high level and the low level can always be accurately detected, the frequency of occurrence of communication errors is reduced, A non-contact IC card capable of stable communication can be provided.
[0028]
Further, according to the present invention, the automatic gain control means is provided on the input side of the comparator, and the hysteresis width of the comparator is fixed, so that the high level and the low level can always be detected accurately, and the frequency of occurrence of communication errors is reduced. As a result, it is possible to provide a non-contact type IC card capable of performing stable communication.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically showing a main configuration of a non-contact type IC card according to a first embodiment of the present invention.
FIG. 2 is a waveform diagram of an input signal and an output signal of a comparator according to the related art.
FIG. 3 is a waveform diagram of an input signal and an output signal of a comparator according to the first embodiment of the present invention.
FIG. 4 is a block diagram schematically showing a main configuration of a non-contact type IC card according to a second embodiment of the present invention.
FIG. 5 is a waveform chart of an input signal of an AGC circuit, an input signal of a comparator, and an output signal according to a second embodiment of the present invention.
[Explanation of symbols]
11 antenna part, 12 full-wave rectifier circuit (rectifier), 13 smoothing circuit, 14 voltage detector circuit (voltage detector), 15 shunt regulator (power supply generator), 16 comparator, 17 current detection Circuits (current detection means), 18 ... control section (hysteresis control means), 19 ... modulation / demodulation section, 20 ... AGC circuit (automatic gain control means).

Claims (5)

A non-contact type IC card that receives an electromagnetic wave transmitted from an external device, generates an operating voltage using the received electromagnetic wave, operates, and performs predetermined data processing and the like by performing wireless communication with the external device. At
An antenna unit for performing wireless communication with an external device,
Rectifying means for rectifying a received signal obtained from the output of the antenna unit;
Power supply generating means for generating an operating voltage of the contactless IC card from the received signal rectified by the rectifying means;
A comparator having a hysteresis characteristic for obtaining reception data by binarizing the reception signal rectified by the rectification means;
Hysteresis control means for varying the hysteresis width of the comparator according to the level of the received signal;
A non-contact type IC card, comprising: Further comprising voltage detection means for detecting the output voltage of the rectification means,
2. The non-contact method according to claim 1, wherein the hysteresis control unit uses a voltage value detected by the voltage detection unit as a level of a received signal, and varies a hysteresis width of the comparator according to the voltage value. Type IC card. Further comprising current detection means for detecting a current flowing from the power generation means,
2. The non-contact method according to claim 1, wherein the hysteresis control unit uses a current value detected by the current detection unit as a level of a received signal, and varies a hysteresis width of the comparator according to the current value. Type IC card. Voltage detecting means for detecting an output voltage of the rectifying means, and a current detecting means for detecting a current flowing from the power generating means,
The hysteresis control unit uses a voltage value detected by the voltage detection unit and a current value detected by the current detection unit as a level of a reception signal, and sets a hysteresis width of the comparator according to the voltage value and the current value. The non-contact type IC card according to claim 1, wherein the IC card is varied. A non-contact type IC card that receives an electromagnetic wave transmitted from an external device, generates an operating voltage using the received electromagnetic wave, operates, and performs predetermined data processing and the like by performing wireless communication with the external device. At
An antenna unit for performing wireless communication with an external device,
Rectifying means for rectifying a received signal obtained from the output of the antenna unit;
Power supply generating means for generating an operating voltage of the contactless IC card from the received signal rectified by the rectifying means;
A comparator having a hysteresis characteristic for obtaining reception data by binarizing the reception signal rectified by the rectification means;
Automatic gain control means provided on the input side of the comparator for controlling the input signal level to the comparator to be constant;
A non-contact type IC card, comprising:

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