JP2004110815A - Noncontact ic card reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the immediate responsiveness by rapidly performing the detection of the advancing state of a noncontact IC card to a communication area, and to minimize the processing load of a communication control means. <P>SOLUTION: A CPU 4 performs a control for transmitting a non-modulated standard carrier wave signal Sc from a transmitting circuit 3 to the communication area through a magnetic field type antenna 1. A wave detection circuit 6 detects the output of the transmitting circuit 3. When the IC card 2 is advanced into the communication area, the impedance of the antenna 1 is changed, and the detection output by the wave detection circuit 6 is also fluctuated thereby. A determination circuit 7 determines the advance of the IC card 2 to the communication area based on the fluctuation quantity of the detection output of the wave detection circuit 6, and gives an advance detection signal Sa to the CPU 4 when the advance is determined. The CPU 4 transmits a detection command to the communication area on receipt of the advance detection signal Sa, and starts the data communication operation with the IC card 2 when a response is received from the IC card 2 according to this. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a non-contact IC card reader using a magnetic field type antenna.

As this type of non-contact IC card reader, a non-contact IC card reader / writer used for an automatic ticket gate, an individual authentication system, and the like is known. In such a non-contact IC card reader / writer, a sensor mechanism for detecting that a non-contact IC card (hereinafter, simply referred to as an IC card) has entered a communication area of a magnetic field type antenna has been omitted. For this purpose, there is provided a configuration in which a state in which an IC card enters a communication area is detected based on whether or not communication with the IC card is enabled. Specifically, in this device, an operation of transmitting (polling) a detection command from the antenna to the communication area at predetermined time intervals is executed at a fixed period, and a response signal is transmitted from the IC card receiving the detection command to an answer back. Then, a detection operation for determining that the IC card has entered the communication area when performed is performed (for example, see Patent Document 1).
JP 2001-143023 A

(4) The IC card reader / writer is required to improve the immediate response. However, when the immediate response is to be improved, the transmission cycle of the detection command needs to be shortened in the above-described conventional IC card reader / writer. However, when the transmission cycle of the detection command is shortened in this way, the processing load on the communication control means (generally constituted by a CPU) provided for controlling the communication operation by the IC card reader / writer increases. Therefore, it is necessary to increase the processing capacity, and this causes a problem that the apparatus cost is increased. Further, when the response time to the detection command on the IC card side is long, there is also a problem that the time lag until the detection of the IC card increases by that much. Such a problem is caused by a system in which the same user can use two or more IC cards, for example, a system for paying a fee using an IC card configured as a subtractive prepaid card, or a system owned by different users. There is a situation in which a door lock is unlocked only when two or more IC cards are collected.

The present invention has been made to solve the above problems, and an object of the present invention is to quickly detect a state in which a non-contact IC card has entered a communication area, thereby improving immediate responsiveness. Another object of the present invention is to provide a non-contact IC card reader device capable of reducing the processing load of communication control means, and a non-contact IC capable of realizing a reduction in power consumption in addition to such effects. A card reader device is provided.

The communication control means transmits a reference carrier signal of a predetermined frequency from a magnetic field type antenna to a communication area, and a non-contact IC card is provided in the communication area during the transmission period. Enters, the IC card and the antenna are electromagnetically coupled, and the electrical characteristics of the antenna change. When the electrical characteristics of the antenna change, the change is detected by the detecting means. Then, the determining means determines whether or not the non-contact IC card has entered the communication area based on the amount of change in the detection output by the detecting means. Will be output. When the entry detection signal is output as described above, the communication control unit transmits a detection command toward the communication area, and the communication control unit receives a response from the non-contact IC card receiving the detection command. The data communication with the IC card is started.

In other words, according to the first aspect of the present invention, when the non-contact IC card enters the communication area, the entry detection signal indicating that the non-contact IC card indicates the response time to the detection command on the IC card side is short. It will be output completely unrelated. For this reason, the state in which the non-contact IC card has entered the communication area can be detected more quickly than in the conventional configuration, and the immediate responsiveness can be improved. Further, the communication control means only needs to perform the processing of transmitting the detection command for the first time when the entry detection signal is received, so that the communication control means needs to shorten the transmission cycle of the detection command as in the conventional configuration. There is no danger of the load increasing. For this reason, it is not necessary to increase the processing capability of the communication control means, and the apparatus cost can be reduced.

According to the second aspect, the transmission output of the reference carrier signal transmitted toward the communication area is suppressed to a level smaller than the transmission output at the time of transmitting the detection command and at the time of data communication. The power consumption during the standby period until the non-contact IC card enters can be suppressed.

In the means according to claim 3, the communication control means transmits a reference carrier signal of a predetermined frequency from the magnetic field type antenna to the communication area, and transmits the transmission power during the transmission period from the steady state power through the current control means. It will be kept in the lowered state. When a non-contact IC card enters the communication area from this state, the IC card and the antenna are electromagnetically coupled, and the impedance of the antenna changes. When the impedance of the antenna changes in this manner, the sampling voltage provided by the sampling means provided to sample the average value of the output voltage of the current control means changes. It is possible to detect that the non-contact IC card has entered the communication area based on the amount of change in the voltage. When such a detection operation is performed, the communication control means returns the transmission power to the steady-state power through the current control means, and starts transmitting a detection command toward the communication area. When a response is received from the non-contact IC card that has received the data, the data communication with the IC card starts.

In other words, according to the means of claim 3, when the non-contact IC card enters the communication area, the operation of detecting the entry state is completely different from the response time to the detection command on the IC card side. Since the detection is performed irrespective, the state in which the non-contact IC card has entered the communication area can be detected more quickly than in the conventional configuration, and the immediate response can be improved. Further, the communication control means only needs to perform a process of transmitting a detection command for the first time when the entry of the non-contact IC card into the communication area is detected, so that the processing load on the communication control means does not increase. Thus, it is not necessary to increase the processing capability of the communication control means, and the cost of the apparatus can be reduced. In addition, during the transmission period of the reference carrier signal toward the communication area, the transmission power is maintained at a level lower than the steady-state power, so that the power consumption during the standby period until the non-contact IC card enters the communication area. Can be suppressed.

According to the fourth aspect of the present invention, when the state where the non-contact IC card has entered the communication area is not detected for some reason (for example, the state where the non-contact IC card has already entered the communication area) ), The data communication with the non-contact IC card can be started in response to the intermittent transmission of the detection command. Will be higher. However, the intermittent transmission operation of the detection command is a complementary operation for coping with a case where the detection of the approach state of the non-contact IC card into the communication area has failed, and the transmission cycle of the detection command is determined by the communication control. The range is set so that the processing load on the means does not increase.

According to the fifth aspect of the present invention, since the transmission of the reference carrier signal is performed intermittently, it is possible to suppress the power consumption during the standby period until the non-contact IC card enters the communication area.

According to the means described in claim 6, the entry detection signal is output from the determination means only when the non-contact IC card enters the detection area set in a range narrower than the communication area. Therefore, there is no possibility that data communication is started near the communication limit with the non-contact IC card, and data communication can be performed in a stable state at all times.

According to the seventh aspect of the present invention, when a foreign object such as a metal plate enters the communication area, the impedance of the antenna electromagnetically coupled to the foreign object greatly changes, so that the detection output of the detecting unit changes. The amount exceeds the set level, and accordingly, an abnormal signal is output from the determination means. When the abnormal signal is output as described above, the communication control unit performs control to suppress the start of the transmission operation of the detection command or the start of the data communication operation. As a result, it is possible to prevent a situation in which an excessive load current flows as a foreign matter other than the non-contact IC card enters the communication area.

(First Embodiment)
Hereinafter, a first embodiment in which the present invention is applied to a non-contact IC card reader / writer will be described with reference to FIGS.
FIG. 1 schematically shows an electrical configuration of a contactless IC card reader according to the present embodiment by combining functional blocks. In FIG. 1, an antenna 1 is of a magnetic field type formed of, for example, a loop antenna, and is electromagnetically coupled to a non-contact IC card (hereinafter simply referred to as an IC card) 2 existing in a predetermined communication area. ing. Although not shown, the antenna 1 is connected to an impedance matching circuit for performing optimum electromagnetic coupling with the IC card 2.

A transmission circuit 3 that performs a transmission operation through the antenna 1 includes, for example, a modulation circuit that performs ASK (Amplitude Shift Keying) modulation, and operates based on a command from a CPU 4 (corresponding to communication control means). . A receiving circuit 5 that performs a receiving operation through the antenna 1 includes an ASK demodulation circuit and the like, and is configured to supply a received signal to the CPU 4. The communication frequency (carrier frequency) of the transmitting circuit 3 and the receiving circuit 5 is set to 13.56 MHz. Although not shown, the CPU 4 has a configuration capable of performing data communication with an external host device (such as a personal computer). However, a configuration capable of performing such data communication may be adopted as needed.

The CPU 4 always transmits the non-modulated reference carrier signal Sc (having a frequency of 13.2) as schematically shown in FIG. 2A from the transmission circuit 3 during a period in which data communication with the IC card 2 is not performed. 56 MHz), and the reference carrier signal Sc at a certain level is transmitted from the antenna 1 to the communication area described above in response to the output. In this case, when the IC card 2 enters the communication area, the impedance of the antenna 1 electromagnetically coupled to the IC card 2 changes, and the impedance is output from the transmission circuit 3 according to the change in the electrical characteristics of the antenna 1. The level of the reference carrier signal Sc changes as schematically shown in FIG. Although not shown in FIG. 2B, when the IC card 2 leaves the communication area, the level of the reference carrier signal Sc returns to the original state. Therefore, by monitoring the level of the reference carrier signal Sc, it is possible to determine whether the IC card 2 has entered or left the communication area. Further, when a foreign substance such as a metal plate enters the communication area, the impedance of the antenna 1 greatly changes. Therefore, the entry of the foreign substance into the communication area can be detected by monitoring the level of the reference carrier signal Sc.

波 The detection circuit 6 (corresponding to detection means) detects the output of the transmission circuit 3 and supplies the detected signal to the judgment circuit 7 (corresponding to judgment means). FIG. 3 schematically shows an example of a detection output by the detection circuit 6. That is, FIG. 3A shows an output example when the unmodulated reference carrier signal Sc shown in FIG. 2A is detected, and FIG. 3B shows the output of the reference carrier signal Sc ( FIG. 3 (c) shows an output when detecting the reference carrier signal Sc when the IC card 2 leaves the communication area (a signal when the IC card 2 enters the communication area). FIG. 3D shows an output example when the reference carrier signal Sc is detected when a foreign substance such as a metal plate enters the communication area.

In this case, the CPU 4 is configured to continuously supply the synchronization signal Sy to the determination circuit 7 during a period in which the transmission circuit 3 outputs the reference carrier signal Sc. The determination circuit 7 determines a change amount of the detection output by the detection circuit 6 during a period in which the synchronization signal Sy is given from the CPU 4 to a first threshold value which is set in advance (indicated by -ΔT1 in FIG. 3B). By comparing with the above, it is determined whether or not the IC card 2 has entered the communication area, and when it is determined that the IC card 2 has entered, the entry detection signal Sa is output to the CPU 4. In addition, the determination circuit 7 determines the amount of change in the detection output by the detection circuit 6 during the period in which the synchronization signal Sy is given from the CPU 4 to a second predetermined threshold value (shown by + ΔT2 in FIG. 3C). By comparing with the above, it is determined whether or not the IC card 2 has left within the communication area, and when it is determined that the IC card 2 has left, the release detection signal Sb is output to the CPU 4. Further, the determination circuit 7 indicates the amount of change in the detection output by the detection circuit 6 during the period in which the synchronization signal Sy is given from the CPU 4 to a third threshold value set in advance (-ΔT3 in FIG. 3D). : Equivalent to the set level in the invention according to claim 5), it is determined whether or not a foreign object such as a metal plate has entered the communication area, and when it is determined that the foreign object has entered, an abnormal signal is output. Sz is output to the CPU 4.

In this example, values (−ΔT1, + ΔT2, −ΔT3) based on the level of the detection signal in a steady state (see FIG. 3A) are set as the first to third thresholds. However, the configuration may be such that values ΔT1 ′, ΔT2 ′, and ΔT3 ′ (see FIGS. 3B, 3C, and 3D) are set with reference to the zero level.

FIG. 4 schematically shows an example of a card recognition sequence when the IC card 2 enters the communication area. That is, in FIG. 4, when the IC card 2 enters the communication area, the determination circuit 7 supplies the CPU 4 with the entry detection signal Sa. Then, the CPU 4 causes the transmission circuit 3 to start outputting the detection command, whereby the detection command is transmitted from the antenna 1 toward the inside of the communication area. This detection command is received by the IC card 2 that has entered the communication area, and the IC card 2 returns a response signal.

応 答 This response signal is provided from the antenna 1 to the CPU 4 through the receiving circuit 5. Upon receiving the response signal, the CPU 4 recognizes (detects) that the IC card 2 has entered the communication area by the antenna 1 and allocates a unique ID to the IC card 2 based on the recognition state to establish a communication link. At the same time, the data transmission / reception operation using the ID is performed to read data stored in the memory of the IC card 2 and write data. In this case, if no response signal is returned from the IC card 2 after the transmission of the detection command, the CPU 4 returns to a state of waiting until the entry detection signal Sa is input.

When the IC card 2 is separated from the communication area (when the communication link is canceled) from the state where the IC card 2 is present in the communication area as described above, the determination circuit 7 detects the separation from the CPU 4. Signal Sb is provided. The CPU 4 receiving the detachment detection signal Sb recognizes (detects) that the IC card 2 has detached from the communication area.

Note that the IC card 2 in a state where a communication link has been established with the IC card reader / writer is set not to return a response signal even if a detection command is received thereafter. When two IC cards 2 enter the communication area at the same time, a response signal is returned from each of the IC cards 2 in response to the transmission of the detection command. The state in which the card 2 has entered at the same time can be determined by signal processing on the CPU 4 side.

FIG. 5 shows a state where the first IC card 2 has already entered the communication area, a case where the second IC card 2 has entered the communication area, and thereafter the first IC card 2 2 schematically shows a card recognition sequence in the case where 2 has left the communication area. That is, in FIG. 5, when the second IC card 2 enters the communication area, the determination circuit 7 supplies the CPU 4 with the entry detection signal Sa. Then, the CPU 4 causes the transmission circuit 3 to start outputting the detection command, whereby the detection command is transmitted from the antenna 1 toward the inside of the communication area. This detection command is received by the two IC cards 2 that have entered the communication area. However, the first IC card 2 returns a response signal because the communication link has already been established. Is not performed, and only the second IC card 2 returns a response signal.

応 答 This response signal is provided from the antenna 1 to the CPU 4 through the receiving circuit 5. When receiving the response signal, the CPU 4 recognizes (detects) that the second IC card 2 has entered the communication area by the antenna 1 and assigns a unique ID to the IC card 2 based on the recognition state. In addition to establishing a communication link, a data transmission / reception operation using the ID is performed to read data stored in a memory in the IC card 2 and write data. In this case, if no response signal is returned from the IC card 2 after the transmission of the detection command, the CPU 4 returns to a state of waiting until the entry detection signal Sa is input.

When the first IC card 2 leaves the communication area (when the communication link is released) from the state where two IC cards 2 are present in the communication area as described above, the determination circuit is provided. 7 to the CPU 4. The CPU 4 that has received the detachment detection signal Sb transmits a confirmation command S1 to the first IC card 2. The first IC card 2 is set to return a confirmation response R1 to the CPU 4 when the confirmation command S1 is received. In this case, since the communication link has been canceled, the confirmation command S1 is transmitted. No acknowledgment R1 can be received, and no acknowledgment R1 is returned.

The CPU 4 waits until a certain time τ elapses after the transmission of the confirmation command S1. If the confirmation response R1 is not received within the waiting period, the first IC card 2 is removed from the communication area. Is recognized (detected). In this case, it is assumed that the state in which the detachment detection signal Sb is output from the determination circuit 7 corresponds to a state in which the two IC cards 2 have simultaneously detached from the communication area. The confirmation command S2 is transmitted to the card 2. The second IC card 2 is set to return a confirmation response R2 to the CPU 4 when the confirmation command S2 is received. In the example described here, the second IC card 2 is located within the communication area. Therefore, the confirmation response R2 is returned. Thereby, the CPU 4 can recognize that the two IC cards 2 are not simultaneously removed.

If the two IC cards 2 are simultaneously removed from the communication area, that is, if the CPU 4 does not receive the acknowledgment R2 in the above example, the CPU 4 sends a detection command to the communication area just in case. May be transmitted to confirm whether there is an IC card 2 in a state where a communication link is not established in the communication area.
Further, although not shown, when the CPU 4 receives the abnormal signal Sz from the determination circuit 7, the CPU 4 is configured to perform control for suppressing the start of the transmission operation of the detection command or the start of the data communication operation.

In short, in the IC card reader / writer having the above-described configuration, the reference carrier signal Sc of a fixed level is transmitted from the magnetic field type antenna 1 to the communication area during the period in which data communication with the IC card 2 is not performed. When the IC card 2 enters the communication area during the transmission period, the IC card 2 and the antenna 1 are electromagnetically coupled, so that the electrical characteristics (impedance) of the antenna 1 are reduced. And the level of the reference carrier signal Sc output from the transmission circuit 3 changes. When the level of the reference carrier signal Sc changes in this way, the change is detected by the detection circuit 6. The determination circuit 7 determines whether or not the IC card 2 has entered the communication area based on the amount of change in the detection output by the detection circuit 6, and detects the entry when it is determined that the IC card 2 has entered. The signal Sa is output and given to the CPU 4. Upon receiving the entry detection signal Sa, the CPU 4 transmits a detection command toward the communication area. When a response is received from the IC card 2 that has received the detection command, the data between the IC card 2 and the IC card 2 is transmitted. Communication starts.

That is, according to this configuration, when the IC card 2 enters the communication area, the entry detection signal Sa indicating this is immediately output regardless of the response time to the detection command on the IC card 2 side. Since the output is performed, the state in which the IC card 2 has entered the communication area can be detected more quickly than in the conventional configuration, and the immediate response can be improved. Further, since the CPU 4 does not need to shorten the transmission cycle of the detection command as in the conventional configuration, there is no possibility that the processing load increases. For this reason, it is not necessary to increase the processing capacity of the CPU 4 and the cost of the apparatus can be reduced.

In this case, even when the IC card 2 is removed from the communication area, the level of the reference carrier signal Sc output from the transmission circuit 3 changes, and the detection output of the detection circuit 6 also changes. Is configured to output a detachment detection signal Sb indicating that the IC card 2 has detached from the communication area 2 based on such an amount of change, so that the detachment of the IC card 2 from the communication area is also quickly detected. You can do it.

When a foreign substance such as a metal plate enters the communication area, the impedance of the antenna 1 electromagnetically coupled to the foreign substance greatly changes, and the amount of change in the detection output by the detection circuit 6 increases. In this embodiment, when the change amount exceeds the set level (third threshold value -ΔT3), the judgment circuit 7 outputs the abnormality signal Sa, and the CPU 4 receiving the signal outputs the abnormality signal Sa. It is configured to perform control for suppressing a transmission operation or a data communication operation with the IC card 2. Therefore, it is possible to prevent an excessive load current from flowing when a foreign matter other than the IC card 2 enters the communication area, and the switching element and the like provided in the transmission circuit 3 may cause an excessive load current. Eliminates the risk of being destroyed.

In this embodiment, the CPU 4 is provided with a control function of suppressing the transmission output of the reference carrier signal Sc to a level smaller than the transmission output at the time of transmitting the detection command and at the time of data communication with the IC card 2. May be added. When such a function is added, it is possible to reduce the power required for transmitting the reference carrier signal Sc during the standby period until the IC card 2 enters the communication area, thereby suppressing power consumption. Become.

Further, a control function of intermittently executing the transmission control of the reference carrier signal Sc at predetermined intervals may be added to the CPU 4, and in this case, the control function until the IC card 2 enters the communication area may be added. Power consumption during the standby period can be suppressed.
Further, the CPU 4 sets the transmission output level of the reference carrier signal Sc to a level at which the entry detection signal Sa is output from the determination circuit 7 in a state where the IC card 2 enters the detection area set to a range narrower than the communication area. It may be configured to perform control for suppression. According to this configuration, the entry detection signal Sa is output from the determination circuit 7 only when the IC card 2 enters the detection area set to be smaller than the communication area. Therefore, there is no possibility that data communication is started near the communication limit with the IC card 2, and data communication can be performed in a stable state at all times.

(Second embodiment)
FIG. 6 shows a second embodiment of the present invention, and only the portions different from the first embodiment will be described below.
In this embodiment, when the second IC card 2 enters the communication area, a sequence for confirming whether the first IC card 2 has left the communication area is added. It is characterized by the following points. FIG. 6 is a sequence diagram corresponding to FIG. 5 in the first embodiment. When the CPU 4 recognizes that the second IC card 2 has entered the communication area by the antenna 1, The confirmation command S1 is transmitted to the IC card 2. In this case, since the confirmation response R1 is returned when the first IC card 2 remains in the communication area, the CPU 4 can confirm that the IC card 2 has not left the communication area. After this confirmation, the CPU 4 waits until the departure detection signal Sb is input, as in the case of the first embodiment. Further, if the confirmation response R1 is not received even after a certain time τ has elapsed after the transmission of the confirmation command S1, the CPU 4 determines that one IC card 2 has entered the communication area when the second IC card 2 has entered the communication area. It is possible to recognize that the eye IC card 2 has left the communication area.

(Third embodiment)
FIG. 7 shows a third embodiment of the present invention. Hereinafter, only a portion different from the first embodiment will be described.
This embodiment is characterized in that the received signal of the antenna 1 is detected by the detection circuit 6 as shown in FIG. Even with this configuration, the detection circuit 6 can obtain a detection output that fluctuates according to a change in the impedance of the antenna 1, so that the same effect as in the first embodiment can be obtained.

(Fourth embodiment)
FIG. 8 shows a fourth embodiment of the present invention. Hereinafter, only a portion different from the first embodiment will be described.
In this embodiment, as shown in FIG. 8, a search coil 8 whose impedance changes according to the entry of the IC card 2 into the communication area is provided, and the output of the search coil 8 is detected by the detection circuit 6. It is characterized by having done. According to this configuration, since the impedance change of the search coil 8 according to the entry of the IC card 2 into the communication area can be always detected by the detection circuit 6, the same effect as in the first embodiment can be obtained. Note that a configuration in which the function of detecting the IC card 2 by the search coil 8 and the function of detecting the IC card 2 according to the first embodiment are also possible.

(Fifth embodiment)
FIG. 9 shows a fifth embodiment of the present invention. Only parts different from the first embodiment will be described below.
In this embodiment, as shown in FIG. 9, the CPU 4 is provided with an A / D conversion function for converting the detection output of the detection circuit 6 into a digital signal, and the determination program described in the first embodiment by the processing program of the CPU 4. 7 is realized.

(Sixth embodiment)
FIGS. 10 to 13 show a sixth embodiment of the present invention, and only the portions different from the first embodiment will be described below.
In FIG. 10, the antenna 1 is shown by an equivalent circuit, and the antenna 1 is of a so-called series-parallel type in which the effective inductance, the effective resistance, and the effective capacitance are connected between feed points as shown in the drawing. The transmission filter 9 that functions as an impedance matching circuit for the antenna 1 is configured to include a series-connected inductor and the like. In this embodiment, the number of the series inductors is adjusted to adjust the number of the series inductors. It is designed such that when the IC card enters the communication area, the impedance of the transmission system including the antenna 1 and the transmission filter 9 changes in a direction to increase.

The transmission circuit 11 (current control means) whose operation is controlled by the CPU 10 (corresponding to communication control means and detection means) has a MOS transistor (not shown) in the output stage, and is provided to the antenna 1 through the transmission filter 9. The transmission power can be adjusted in a plurality of stages (for example, 35 stages) by current control. The reference carrier signal Sc output from the transmission circuit 11 is a signal having a frequency of 13.56 MHz and a peak value voltage of 5V. However, especially the peak value voltage of the reference carrier signal Sc is changed to various values according to the circuit specifications.

The integrating circuit 12 (sampling means) including the capacitor 12a and the resistor 12b is set to a small time constant that does not affect the transmission output, and samples the average value of the output voltage from the transmission circuit 11, and The configuration is such that a sampling voltage is supplied to the CPU 10 via an A / D converter 13 having a resolution of, for example, 10 bits.
In FIG. 10, a receiving circuit that performs a receiving operation through the antenna 1 is not shown. Actually, the CPU 10, the transmission circuit 11, the integration circuit 12, the A / D converter 13, and the transmission circuit (not shown) are formed on a custom IC.

In the following, the principle of detecting a non-contact IC card by the card reader device having the above configuration will be described with reference to FIGS. However, in FIGS. 11 to 13, an equivalent electrical configuration of a main part in FIG. 10 in a state where a MOS transistor provided in an output stage of the transmission circuit 11 is represented by a resistor R corresponding to its ON resistance value. It is shown.
(1) At the time of steady output To obtain the transmission output corresponding to the constant power, the impedance of the transmission system (the antenna 1 and the transmission filter 9) viewed from the transmission circuit 11 side is the impedance of the output stage MOS transistor. It is designed to appear to be about five times the ON resistance value. In the present embodiment, as shown in FIG. 11, the impedance of the transmission system designed as described above is indicated as z1 (Ω). If the resistance value of the resistor R in a state where the current output level of the transmission circuit 11 is set to the maximum value is r1 (Ω), a pulse signal output from the transmission circuit 11 is output from the output point of the integration circuit 12. A sampling voltage (= {r1 / (z1 + r1)}) obtained by averaging a signal obtained by dividing a peak value voltage (= 5V) by a resistor R (= r1 (Ω)) and an impedance of a transmission system (= z1 (Ω)) / 2) is output. In the present embodiment, z1 and r1 are set to values such that the sampling voltage is about 2.0 V.

(2) At Card Standby At the time of contactless IC card standby, the current output level of the transmission circuit 11 is set to the minimum value. If the transmission output at this time is, for example, about 20% of the maximum output, the ON resistance value of the output stage MOS transistor of the transmission circuit 11 will increase greatly, as shown in FIG. In addition, the resistance value of the resistor R is r2 (Ω) which is several times larger than the resistance value r1. In this case, since the impedance of the transmission system remains at z1 (Ω), the amount of voltage drop at the resistor R relatively increases, and as a result, the level of the sampling voltage output from the integration circuit 12 becomes relatively high. descend. That is, from the output point of the integration circuit 12, the peak value voltage (= 5V) of the pulse signal output from the transmission circuit 11 is converted to the resistance R (= r2 (Ω)) and the impedance of the transmission system (= z1 (Ω)). )), A sampling voltage (= {r2 / (z1 + r2)} / 2) obtained by averaging the divided signals is output. In the present embodiment, z1 and r2 are replaced by, for example, about 0. The value is set to be about .92V. With such a setting, the current (effective value) flowing through the resistor R becomes less than half the level at the time of steady output by simple calculation.

(3) When approaching the card When the card is waiting, the impedance of the transmission system when the non-contact IC card 2 (effective inductance, effective resistance, and effective capacitance are shown by an equivalent circuit) enters the communication area of the antenna 1, When the simulation is performed with the coupling count k between the two set to 0.05, as shown in FIG. 13, the value increases from z1 (Ω) to z2 (Ω) which is about 1.5 times the value. Accordingly, the amount of voltage drop at the resistor R is relatively reduced. Therefore, from the output point of the integration circuit 12, the peak value voltage (= 5V) of the pulse signal output from the transmission circuit 11 is converted to the resistance R (= r2 (Ω)) and the impedance of the transmission system (= z2 ( Ω)), a sampling voltage (= {r2 / (z2 + r2)} / 2) obtained by averaging the divided signals is output. In the present embodiment, the sampling voltage is, for example, about z2 and r2. The value is set to be about 1.2 V.

That is, when the non-contact IC card 2 enters the communication area of the antenna 1 in the card standby state, the sampling voltage rises from about 0.92V to about 1.2V. Since the A / D converter 13 receiving this sampling voltage has a resolution of 10 bits, if the input voltage range is, for example, 3.3 V, it is possible to detect 3.3 V / 1024 ≒ 3.2 mV. is there. Therefore, a change in the sampling voltage from 0.92 V to 1.2 V can be observed as a sufficiently large change.

On the other hand, the CPU 10 performs control to switch the current output level of the transmission circuit 11 to the minimum value during card standby (the transmission period of the reference carrier signal Sc), thereby maintaining the transmission power lower than the steady state power. . Further, the CPU 10 determines (detects) whether or not the non-contact IC card 2 is in a state of entering the communication area by the antenna 1 based on the change amount of the sampling voltage given through the A / D converter 13. When it is determined that the non-contact IC card 2 has entered the communication area, the transmission power of the transmission circuit 11 is returned to the steady-state power, and the control for starting the detection command transmission operation is performed. .

In short, according to the above-described embodiment, when the non-contact IC card 2 enters the communication area of the antenna 1, the operation of detecting the entry state is shortened in response time to the detection command on the IC card 2 side. Is performed irrespective of this, the state in which the non-contact IC card 2 enters the communication area can be detected more quickly than in the conventional configuration, and the immediate response can be improved. Further, since the CPU 10 only needs to perform the process of transmitting the detection command for the first time when the entry of the non-contact IC card into the communication area is detected, there is no possibility that the processing load on the CPU 10 increases. Therefore, it is not necessary to increase the processing capability of the CPU 10, and the cost of the apparatus can be reduced. Moreover, during the transmission period of the reference carrier signal Sc toward the communication area, the transmission power is maintained at a level lower than the steady-state power, so that the non-contact IC card 2 enters the communication area in a standby period. The power consumption can be reduced.

In the present embodiment, a signal (sampling signal) obtained by dividing the peak value voltage of the pulse signal from the transmission circuit 11 and averaging the divided voltage is input to the A / D converter 13. Therefore, there is no possibility that the input voltage exceeds the power supply voltage of the A / D converter 13. For this reason, it is not necessary to provide a voltage dividing circuit for preventing the input voltage from exceeding the power supply voltage in the preceding stage of the A / D converter 13, so that the circuit configuration can be simplified. Incidentally, conventionally, since a signal received by the receiving circuit is converted into a digital signal by the A / D converter, the input voltage of the A / D converter may exceed the power supply voltage. There is a problem that a voltage dividing circuit is required to deal with the problem, and the circuit configuration is complicated.

(Other embodiments)
Note that the present invention is not limited to the above-described embodiment, and can be modified or expanded as described below.
Various forms of the IC card reader / writer can be considered, such as an insertion / extraction type and a touch-and-go type. Also, the writer function is not particularly necessary. The present invention can also be applied to an apparatus having only a reader function.
In each of the above-described embodiments, the detection command transmission operation is not performed in the standby state of the non-contact IC card 2. However, the content of the control by the CPU 4 or 10 is determined during the standby period (during the transmission period of the reference carrier signal Sc). , The transmission operation of the detection command may be performed intermittently. According to this configuration, when the state where the non-contact IC card 2 has entered the communication area of the antenna 1 is not detected for some reason (for example, when the non-contact IC card 2 has already entered the communication area) Data communication with the non-contact IC card 2 can be started in response to the intermittent transmission of the detection command even when the transmission of the reference carrier signal is started from the state where the reference carrier signal is transmitted. The nature becomes high. However, the intermittent transmission operation of the detection command is a complementary operation for coping with a case where the detection of the state of entry of the non-contact IC card 2 into the communication area has failed. Alternatively, it is set to a range where the processing load at 10 does not increase.
In the sixth embodiment, the transmission system is configured to increase the impedance when the non-contact IC card 2 approaches, but it is needless to say that the impedance may decrease when the non-contact IC card 2 approaches.

Functional block diagram showing a first embodiment of the present invention The figure which shows typically the example of a waveform of a reference carrier signal The figure which shows typically the example of the detection output by the detection circuit Sequence diagram for explanation of operation 1 Sequence diagram 2 for explaining the operation FIG. 5 corresponding to FIG. 5 showing a second embodiment of the present invention. FIG. 1 corresponding to FIG. 1 showing a third embodiment of the present invention. FIG. 1 is a view showing a fourth embodiment of the present invention and is equivalent to FIG. FIG. 5 is a view corresponding to FIG. 1 showing a fifth embodiment of the present invention. An electrical configuration diagram showing a main part of a sixth embodiment of the present invention. Electrical configuration diagram 1 for explaining operation Electrical configuration diagram 2 for explaining operation Electrical configuration diagram 3 for explanation of operation

Explanation of reference numerals

1 is an antenna, 2 is a non-contact IC card, 3 is a transmission circuit, 4 is a CPU (communication control means), 5 is a reception circuit, 6 is a detection circuit (detection means), 7 is a judgment circuit (judgment means), 9 is A transmission filter, 10 is a CPU (communication control means, detection means), 11 is a transmission circuit (current control means), 12 is an integration circuit (sampling means), and 13 is an A / D converter.

Claims (7)

A reader that transmits a detection command from a magnetic field type antenna to a predetermined communication area and starts data communication with the non-contact IC card when receiving a response from the non-contact IC card that has received the detection command. In the device,
Communication control means for performing control to transmit a reference carrier signal of a predetermined frequency from the antenna toward the communication area,
Detection means for detecting a change in the electrical characteristics of the antenna during the transmission period of the reference carrier signal,
It is determined whether or not the non-contact IC card has entered the communication area based on the amount of change in the detection output by the detection means, and an entry detection signal is output when it is determined that the non-contact IC card has entered the communication area. Judgment means for determining
The non-contact IC card reader device, wherein the communication control means is configured to start transmitting the detection command when the entry detection signal is output. 2. The non-contact communication device according to claim 1, wherein the communication control unit performs control to suppress a transmission output of the reference carrier signal to a level smaller than a transmission output at the time of transmitting the detection command and at a time of the data communication. 3. IC card reader device. A reader that transmits a detection command from a magnetic field type antenna to a predetermined communication area and starts data communication with the non-contact IC card when receiving a response from the non-contact IC card that has received the detection command. In the device,
Current control means capable of adjusting the transmission power given to the antenna by current control,
Sampling means provided to sample the average value of the output voltage from the current control means;
Communication control means for performing control to transmit a reference carrier signal of a predetermined frequency from the antenna toward the communication area,
Detecting means for detecting entry of the non-contact IC card into the communication area based on a change amount of a sampling voltage of the sampling means during a transmission period of the reference carrier signal,
The communication control means controls the current control means to keep the transmission power lower than the steady-state power during the transmission period of the reference carrier signal, and when the detection means shows a detection state. The non-contact IC card reader device is configured to return the transmission power to the steady-state power by the current control unit and perform control to start the transmission operation of the detection command. The non-contact communication device according to any one of claims 1 to 3, wherein the communication control unit is configured to perform the transmission operation of the detection command intermittently during a transmission period of the reference carrier signal. IC card reader device. The non-contact IC card reader device according to any one of claims 1 to 4, wherein the communication control means intermittently executes transmission control of the reference carrier signal at a predetermined cycle. The communication control means outputs the entry detection signal from the determination means in a state where the non-contact IC card enters a detection area set to a range narrower than the communication area, with the transmission output level of the reference carrier signal. The non-contact IC card reader device according to claim 2, wherein the non-contact IC card reader device is controlled to a level set at a predetermined level. The determination means is configured to output an abnormal signal when a change amount of a detection output by the detection means exceeds a set level,
7. The communication control unit according to claim 1, wherein the communication control unit is configured to perform a control to suppress a transmission operation of the detection command or a start of the data communication operation in an output state of the abnormal signal. 8. A non-contact IC card reader device according to any one of the above.

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