JP2005275700A - Noise suppressing method for non-contact ic card reader-writer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always properly receive a response from a non-contact IC card. <P>SOLUTION: The noise suppressing method for the non-contact IC card reader-writer 1 when carrying out exchange of data between the non-contact IC card 2 and the non-contact IC card reader-writer 1 is characterized by that it is provided with a procedure of receiving, amplifying, and demodulating the response from the non-contact IC card 2, a procedure of detecting whether or not there is noise in an amplified reception signal, and a procedure of adjusting a gain of amplification with respect to the reception signal when noise is detected. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a noise suppression method for a non-contact IC card reader / writer when data is exchanged between the non-contact IC card and the non-contact IC card reader / writer.

A communication device including a non-contact IC card and a non-contact IC card reader / writer has been used for various purposes such as work management by a personal information card in a company. In this communication device, when a polling signal is issued from the non-contact IC card reader / writer, the card that has received the response responds in response to a command such as an ID code included in the polling signal. For example, Patent Document 1 discloses a communication apparatus including a non-contact IC card and a non-contact IC card reader / writer.
JP-A-5-314325

By the way, when the non-contact IC card reader / writer receives a response from the non-contact IC card, noise may be received. When noise is received, it may be mistakenly recognized as response data or the response itself may not be recognized.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a noise suppression method for a non-contact IC card reader / writer that can always properly receive a response from a non-contact IC card.

  The present invention has been made paying attention to the following points. That is, the non-contact IC card reader / writer receives, amplifies, and demodulates the response from the non-contact IC card. At this time, if there is noise, adjusting the amplification gain can be expected not to receive the noise as a response during demodulation. Further, when there is noise, by reducing the gain at the noise reception timing, the noise is not erroneously recognized as a received signal with the minimum necessary gain adjustment. Furthermore, when there is noise, it is possible to receive a response without noise by shifting the noise reception timing and receiving the response.

According to the first aspect of the present invention, since it is detected whether or not there is noise in the received signal and the gain of amplification with respect to the received signal of the response is adjusted, the response of the received signal can be normally recognized when demodulated. However, noise can be prevented from being recognized, so that a response from the non-contact IC card can always be properly received.
According to the invention of claim 2, the timing is stored when noise is detected, and from the next time, when the received signal matches the noise detection timing, the received signal is not recognized as a response. This is effective for recognizing a normal response when noise occurs. That is, if noise is detected and its generation timing is measured first, the reception signal generated at the same timing as the noise generation timing is not recognized as a response, so that the response can be recognized without performing the noise detection operation from the next time.

According to the invention of claim 3, when noise is detected, the timing is stored, and from the next time, the response start timing is changed for the non-contact IC card, so that the response is received by shifting the noise reception timing. Therefore, it is possible to receive a noise-free response.
In this case, the response start timing for the non-contact IC card may be changed for each non-contact IC card. Depending on the card, the noise generation timing may be constant. Therefore, according to the fourth aspect of the present invention, even when the noise generation timing is different for each card, a response can be received without receiving noise.

In addition, noise may occur at a certain timing for each command. In this case, the noise is received by changing the response start timing for the card for each command as in the invention of claim 5. You can receive the response without
As in the sixth aspect of the invention, the preamble format of the received signal is compared with the format of the appropriate preamble, and noise detection may be performed when the format of the preamble of the received signal is different from the appropriate preamble. In this way, when noise occurs in the preamble portion of the received signal, it can be reliably detected.

As in the seventh aspect of the invention, the data format of the received signal is compared with a predetermined data format, and noise detection may be performed when the data format of the received signal is different from the predetermined data format. In this way, noise can be reliably detected when noise occurs in the data portion.
When the start value of the data of the received signal is compared with the start value of the data predicted in advance, and the start value of the data of the received signal is different from the start value of the data predicted in advance, It is good also as noise detection. In this way, noise generation can be detected when the leading value of the data is abnormal.

As in the ninth aspect of the invention, noise detection may be performed when a reception signal is received during a time when the non-contact IC card is expected not to return a response. In this way, the occurrence of noise can be detected when there is a received signal at a timing when no response is received.
As in the tenth aspect of the present invention, the time intervals of a plurality of received signals that are detected as noise may be measured, and thereafter, when the received signals are received at the time intervals, they may not be recognized as responses. In this way, noise generated at the same time interval can be prevented from being recognized as a response without performing a noise detection operation.

As in the eleventh aspect, the gain may be adjusted by lowering the gain level each time noise is detected. By doing so, noise is not erroneously recognized as a response even if the noise level is not known.
As in the twelfth aspect of the invention, the non-contact IC card reader / writer may store a table that defines a gain level change mode, and adjust the gain according to this table each time noise is detected. In this way, for example, when a change in the noise level of each response in the card is known, it is possible to immediately set the gain to an appropriate value instead of gradually.

As in the thirteenth aspect of the present invention, the non-contact IC card reader / writer may store a plurality of tables that define gain value change modes, and select one of the tables to perform gain adjustment. In this way, by storing each table according to the card, it is possible to perform gain adjustment using an optimum table for each card.
As in the invention of claim 14, when noise is detected, the magnitude of the noise may be determined, and the gain may be changed in accordance with the magnitude. In this way, optimal gain adjustment can be performed quickly.

  As in the fifteenth aspect of the present invention, an adjustment pattern for adjusting the gain by lowering the gain level each time noise is detected and a table that defines a change form of the gain level may be selected and used. . In this way, it is easy to use.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. First, FIG. 1 schematically shows a configuration of a non-contact IC card reader / writer (hereinafter simply referred to as a reader / writer) 1 and a non-contact IC card (hereinafter simply referred to as an IC card) 2. The reader / writer 1 includes a control circuit 3, a modulation circuit 4, an antenna 5, a demodulation circuit 6, and a memory 7.

  The control circuit 3 controls the overall operation of the reader / writer 1, has a CPU, and is connected to an external host device such as a computer. The modulation circuit 4 modulates the data from the control circuit 3 on a carrier wave, and transmits the modulation signal (data) and the power supply signal from the antenna 5. The demodulating circuit 6 amplifies the return data (received signal) from the IC card 2 at a certain gain level, detects this, and demodulates it. This gain is adjusted by the control circuit 3 as will be described later. The memory 7 manages storage of control firmware and data.

  The IC card 2 also includes an antenna 8 that transmits and receives data using a power carrier wave from the reader / writer 1, a demodulation circuit 9 that detects and demodulates carrier wave data, and a DC signal from the power signal received by the antenna 8. A power supply circuit 10 that generates power, a memory 11 that controls storage of control firmware and data, a control circuit 12 that controls the overall operation of the IC card 2, and a carrier wave that is modulated by information from the control circuit 12 And a modulation circuit 13 for transmitting from the antenna 8.

  The operations of the reader / writer 1 and the IC card 2 will be described with reference to FIG. When a power supply (not shown) is turned on, the reader / writer 1 starts the operation according to the program stored in the memory 7 after the initialization operation of the control circuit 3. The control circuit 3 transmits a power supply signal supplied to the IC card 2 and a polling signal from the antenna 5. This signal is transmitted as an electromagnetic wave (for example, a center carrier frequency of 13.56 MHz).

  Next, when the IC card 2 comes close to the reader / writer 1, the antenna 8 receives a power supply signal, rectifies the carrier wave by the power supply circuit 10, converts it to a DC power supply, and supplies it to all circuits in the card. The control circuit 12 detects and demodulates the command from the reader / writer 1 by the demodulation circuit 9, and analyzes the command. As a result, when it is recognized that it is called, a response is returned from the antenna 8 via the modulation circuit 13.

The response is received by the reader / writer 1 with the antenna 5, amplified by the demodulation circuit 6 with the initial gain, and detected and demodulated. Then, it is analyzed by the control circuit 3 to recognize that the IC card 2 is a card that conforms to the standard. Thereby, communication is performed between the reader / writer 1 and the IC card 2 thereafter.
When the reader / writer 1 receives a response from the IC card 2, the reader / writer 1 detects the presence or absence of noise in the received signal and stores a function for suppressing the noise. Refer to this function (noise suppression method) below. State. The memory 7 of the reader / writer 1 stores a table defining gain level change modes. The concept of the table is as follows. For example, the available gains are divided into 10 levels (from the largest, levels 10, 9, 8,... 1), and the gain levels are, for example, gain levels 9, 6, 5, 8, 5,. It stores a table that changes. Whether or not to use this table can be set in advance in the control circuit 3 from the host device by the manufacturer or the user. This table is suitable when the magnitude for each occurrence of noise is known in advance. That is, depending on the IC card 2, there may be a regularly occurring noise generation pattern, which is suitable in this case. The gain level in the table can also be set from the host device.

Now, as shown in FIG. 2, the reader / writer 1 starts receiving a response after transmitting a command to the IC card 2.
When the reader / writer 1 starts the reception mode (waiting for response), the reader / writer 1 performs amplification and detection processing (step S1). That is, when a signal is received from the IC card 2, the received signal is amplified with an initial gain, detected, and demodulated. When the demodulated signal is recognized as a certain signal (step S2), noise detection processing is performed (step S3). This noise detection process is performed by the noise detection method described above.

  If it is determined that noise has been detected (“YES” in step S4), it is determined whether the gain at this point can be changed (for example, it cannot be changed if it is the minimum gain or the end of the table) (step S5). If the gain can be changed (“YES” in step S5), it is determined whether or not the table is set in advance (step S6). If not, the gain is lowered by one step from the current gain (step S7). That is, when the current gain is 10, the gain is 9. If a table is set in advance, the gain is changed according to this table (step S8).

  Thereafter, the process returns to the amplification / detection process (step S1). At this time, when the noise N2 of FIG. 3 is received and amplified, the gain is lowered, so that the noise N2 is not detected and demodulated, that is, it is determined that there is no received signal. Therefore, the noise N2 is not erroneously recognized as a response. When the normal response signal shown in FIG. 3 is received, in the noise detection process, it is amplified and detected with the current gain, and the demodulated received signal is determined as normal data and recognized as a response. (Step S9).

According to the present embodiment, since it is detected whether or not there is noise in the received signal and the gain of the amplification is adjusted, the probability of recognizing similar noise can be reduced, so Can always be properly received.
Since the gain is adjusted by lowering the gain level every time noise is detected (step S7), the noise is not erroneously recognized as a response even if the noise level is not known. The method of lowering the gain level is not limited to one step, and a plurality of levels may be lowered, or a range of ten steps may be used as appropriate.

In addition, according to the present embodiment, a table defining gain level change forms is stored, and the gain is adjusted according to this table each time noise is detected. When the change in the noise level of the response is known, it is possible to immediately set the gain to an appropriate value instead of gradually.
In addition, according to the present embodiment, it is possible to select between the case where the noise level is gradually lowered and the case where the table is used.

  FIG. 4 shows a second embodiment of the present invention, and the noise suppression method shown in the flowchart of FIG. 4 is suitable for noise suppression in the form shown in FIG. That is, it is determined whether or not the stored regular timing is reached (step R3), and if not, the noise detection process (step R4) similar to step S3 in the first embodiment is performed. If it is noise detection, it is determined whether or not the noise detection is detected three times at the same timing (step R6). Up to the noise N3 in FIG. 5 is “NO”, and the gain is adjusted by a predetermined change method (step S5 to step S8 in the first embodiment) (step R7). If it is detected up to the noise N4 in FIG. 5, “YES” is determined in the step R6, so that the noise detection is stored at a regular timing (step R8).

  Then, when there is a received signal (step R2), if this received signal is stored at regular timing (noise N5 in FIG. 5), this is not recognized as a response signal (step R9). Normally, since the gain is adjusted in step R7, the noises N2 to N4 are rarely detected, but even when this gain adjustment is not performed, the noise N5 is not recognized as a response.

According to this embodiment, noise generated at the same time interval can be prevented from being recognized as a response without performing a noise detection operation.
FIG. 6 shows a third embodiment of the present invention, and the noise suppression method shown in FIG. 6 is suitable for the suppression of noise N1 having a form as shown in FIG. This noise N1 is generated at the same timing from the time when the reader / writer 1 transmits a command to the IC card 2. Such a situation may occur, for example, with a specific IC card.

  That is, when there is a received signal (“YES” in step Q2), the generation timing of this received signal (elapsed time from the command transmission of the reader / writer 1) is measured (step Q3), and this generation timing is already stored. If it is not the same, a noise detection process is performed (step Q5). In the case of noise detection (step Q5, step Q6), the set gain adjustment is performed. The gain is adjusted by the method (step Q7). If the received signal is received at the same timing as the stored timing (“YES” in step Q4), this is judged as noise and is not recognized as a response (step Q8).

According to this embodiment, when a noise signal whose generation timing is known in advance is received, it is not recognized as a response, so that the response can be recognized without performing a noise detection operation.
Embodiments of the present invention are not limited to the above-described embodiments, and may be modified as follows.
1) The reception timing of the received signal determined as noise detection may be measured, and the response start timing may be changed for the non-contact IC card from the next time. In other words, if noise occurs after a certain time, for example, Ta time from the response start timing of the IC card 2, if the next response start timing Ta is changed (for example, changed longer), the received signal is synchronized with the response start timing Ta. If it is recognized as a response, the response can be normally received with a shift from the noise reception timing.

2) In this case, the response start timing for the non-contact IC card may be changed. In this way, even when the noise generation timing is different for each card, it is possible to receive the response by shifting from the noise reception timing.
3) Although noise may occur at a certain timing for each command, in this case, the response start timing for the card may be changed for each command. In this way, a response can be received without receiving noise.

The block diagram which shows the structure of a non-contact IC card and a non-contact IC card reader / writer regarding 1st Example of this invention Flow chart for explaining the noise suppression method Waveform diagram of the received signal before amplification and detection FIG. 2 equivalent view showing a second embodiment of the present invention 3 equivalent figure FIG. 2 equivalent view showing a third embodiment of the present invention. 3 equivalent figure

Explanation of symbols

In the drawings, 1 is a non-contact IC card reader / writer, 2 is a non-contact IC card, 3 is a control circuit, and 6 is a demodulation circuit.

Claims (15)

A non-contact IC card reader / writer noise suppression method when data is exchanged between a non-contact IC card and a non-contact IC card reader / writer,
Receiving, amplifying and demodulating the response from the contactless IC card;
A procedure for detecting whether or not there is noise in the amplified received signal;
And a noise suppression method for a non-contact IC card reader / writer, comprising: a step of adjusting an amplification gain for a received signal when noise is detected. A non-contact IC card reader / writer noise suppression method when data is exchanged between a non-contact IC card and a non-contact IC card reader / writer,
A procedure for receiving a response from a non-contact IC card and detecting whether or not there is noise in the received signal;
A method for suppressing noise in a non-contact IC card reader / writer, comprising: measuring a reception timing of a received signal that is detected as noise, and not recognizing it as a response when the received signal is received at that timing next time . A non-contact IC card reader / writer noise suppression method when data is exchanged between a non-contact IC card and a non-contact IC card reader / writer,
A procedure for receiving a response from a non-contact IC card and detecting whether or not there is noise in the received signal;
Noise suppression of a non-contact IC card reader / writer characterized by comprising a procedure for measuring the reception timing of a received signal determined to be noise detection and changing the response start timing for the non-contact IC card from the next time Method.   4. The noise suppression method for a non-contact IC card reader / writer according to claim 3, wherein the response start timing for the card is changed for each non-contact IC card.   4. The noise suppression method for a non-contact IC card reader / writer according to claim 3, wherein the response start timing for the card is changed for each command.   6. The method according to claim 1, wherein the preamble format of the received signal is compared with the format of the appropriate preamble, and noise detection is performed when the format of the preamble of the received signal is different from the appropriate preamble. Noise suppression method for contact IC card reader / writer.   6. The noise detection is performed by comparing the data format of the received signal with a predetermined data format and determining that the data format of the received signal is different from the predetermined data format. The noise suppression method of the non-contact IC card reader / writer described in 1.   The head value of the data of the received signal is compared with the head value of the data predicted in advance, and noise detection is performed when the head value of the data of the received signal is different from the head value of the data predicted in advance. The noise suppression method of the non-contact IC card reader / writer according to claim 1.   6. The non-contact IC card reader / writer according to claim 1, wherein noise detection is performed when a received signal is received during a time when it is predicted that the non-contact IC card does not return a response. Noise suppression method.   3. The non-contact IC card according to claim 2, wherein a time interval between a plurality of received signals detected as noise is measured, and thereafter, when a received signal is received at the time interval, it is not recognized as a response. Reader / writer noise suppression method.   2. The noise suppression method for a non-contact IC card reader / writer according to claim 1, wherein the gain is adjusted by lowering the gain level each time noise is detected.   2. The non-contact IC card reader / writer stores a table defining gain level change modes, and adjusts the gain according to the table each time noise is detected. IC card reader / writer noise suppression method.   2. The non-contact IC card reader / writer according to claim 1, wherein the non-contact IC card reader / writer stores a plurality of tables defining gain value change modes, and selects one of the tables to perform gain adjustment. Writer noise suppression method.   2. The noise suppression method for a non-contact IC card reader / writer according to claim 1, wherein when noise is detected, the magnitude of the noise is determined and the gain is changed in accordance with the magnitude. 2. The non-contact IC card according to claim 1, wherein an adjustment pattern for adjusting the gain by lowering the gain level each time noise is detected and a table defining a change form of the gain level are selected and used. Reader / writer noise suppression method.

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