JP2008160312A - Radio communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication apparatus which can always acquire optimum communication characteristics not depending on installation environment, a structure of a built-in cabinet, etc. <P>SOLUTION: A contactless IC card reader writer has a resonant circuit including an antenna for performing radio communications using an electromagnetic wave with the contactless IC card, performs transceiving of data by performing radio communications with the contactless IC card through the resonant circuit, and has a transceiving circuit which performs radio communications using the electromagnetic wave with the contactless IC card through the resonant circuit. When a communication characteristic adjustment mode is set, the antenna outputs the electromagnetic waves for adjustment, transmission power of the transceiving circuit is detected at the time, and the resonant frequency of the resonant circuit is adjusted so that the detected transmission power becomes more than a threshold value determined beforehand. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is applied to, for example, a contactless IC card (wireless communication medium) driven by electric power induced by electromagnetic inductive coupling and a contactless IC card reader / writer that transmits and receives data without contact (wireless communication). It is related with a suitable radio communication apparatus.

  Generally, this type of non-contact IC card reader / writer is connected to a host device, and this host device sends a command related to data transmission / reception to the non-contact IC card reader / writer, and from the non-contact IC card reader / writer. A result of communication with a non-contact IC card is received.

The non-contact IC card reader / writer sends an ASK (amplitude shift) modulation signal of a predetermined frequency from the loop antenna to communicate with the non-contact IC card, and the non-contact IC card can communicate with the non-contact IC card reader / writer. When entering the area, operation power is supplied to the non-contact IC card by electromagnetic induction coupling generated between the loop antenna of the non-contact IC card reader / writer and the loop antenna of the non-contact IC card. The non-contact IC card responds to the received data by load modulation, and the non-contact IC card reader / writer detects the load modulation data by envelope detection and demodulates it by the demodulation circuit, and the demodulated data is sent to the host device. It is transferred (for example, see Patent Document 1).
JP-A-10-187916

Currently, contactless IC card reader / writers are used in various environments such as stations and stores. However, the resonance frequency of the resonance circuit including the antenna may deviate from the optimum value depending on the structure of the housing and the installation environment. The magnetic field radiated from the antenna may be absorbed and weakened by the metal casing.
For this reason, in order to realize optimal communication characteristics, there is a problem that it is necessary to adjust the resonance frequency of the resonance circuit including the antenna and the transmission power from the antenna for each structure and installation environment of the housing to be incorporated. .

  Therefore, an object of the present invention is to provide a wireless communication apparatus that can always obtain optimum communication characteristics regardless of the installation environment, the structure of a housing to be incorporated, and the like.

  The wireless communication device of the present invention has a resonance circuit including an antenna for performing wireless communication using an electromagnetic wave with a wireless communication medium, and performs wireless communication with the wireless communication medium via the resonance circuit. In a wireless communication apparatus for performing data transmission / reception by performing, a transmission / reception circuit for performing wireless communication using an electromagnetic wave with a wireless communication medium via the resonance circuit, and the antenna when set to a communication characteristic adjustment mode The adjustment electromagnetic wave is output from the transmission power detection means for detecting the transmission power in the transmission circuit at that time, and the transmission power detected by the transmission power detection means is equal to or greater than a predetermined threshold value. Resonance frequency adjusting means for adjusting the resonance frequency of the resonance circuit.

  The wireless communication device of the present invention has a resonance circuit including an antenna for performing wireless communication using electromagnetic waves with a wireless communication medium, and wirelessly communicates with the wireless communication medium via the resonance circuit. In a wireless communication device that performs transmission and reception of data by performing communication, a transmission / reception circuit that performs wireless communication using an electromagnetic wave with a wireless communication medium via the resonance circuit, and a communication characteristic adjustment mode are set, A transmission power detecting means for outputting an electromagnetic wave for adjustment from the antenna and detecting the transmission power in the transmission circuit at that time, and the transmission power detected by the transmission power detecting means is equal to or greater than a predetermined threshold. And a resonance frequency adjusting means for adjusting the resonance frequency of the resonance circuit, and the adjustment of the resonance frequency of the resonance circuit by the resonance frequency adjusting means is completed. Magnetic field strength detection means for detecting the magnetic field strength in the vicinity of the antenna, and power supply voltage for adjusting the power supply voltage to the transmission / reception circuit so that the magnetic field strength detected by the magnetic field strength detection means is not less than a predetermined threshold value. Adjusting means.

  According to the present invention, the resonance frequency of the resonance circuit including the antenna is automatically adjusted so that the transmission power from the antenna becomes equal to or higher than a predetermined threshold value, so that it does not depend on the installation environment or the structure of the housing to be incorporated. Therefore, it is possible to provide a wireless communication apparatus that can always obtain optimum communication characteristics.

  In addition, according to the present invention, the resonance frequency of the resonance circuit including the antenna is automatically adjusted so that the transmission power from the antenna is equal to or greater than a specified threshold, and the magnetic field strength near the antenna is equal to or greater than the specified threshold. By adjusting the power supply voltage to the transmitter / receiver circuit in this way, even when the resonance frequency is optimized by the structure of the housing to be incorporated, even when the communication distance with the wireless communication medium cannot be taken, the supply to the transmitter / receiver circuit By adjusting the voltage, it is possible to provide a wireless communication device that can obtain optimum communication characteristics.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the first embodiment will be described.
FIG. 1 schematically shows the configuration of a non-contact IC card reader / writer as a wireless communication apparatus according to the first embodiment. This non-contact IC card reader / writer is an example in which wireless communication using electromagnetic waves is performed with the non-contact IC card by placing a non-contact IC card as a wireless communication medium on the antenna unit. Show.

  In FIG. 1, a non-contact IC card reader / writer 1 is connected to a host device 2 that performs command transmission and response processing, and the non-contact IC card 3 is inserted into the antenna unit, so that the non-contact IC card 3 Are configured to perform data transmission / reception such as data reading and writing.

  The non-contact IC card reader / writer 1 includes an antenna (for example, loop antenna) 11 for performing wireless communication using electromagnetic waves with the non-contact IC card 3, a resonance circuit 12 including the antenna 11, and resonance of the resonance circuit 12. Frequency adjustment circuit 13 as a resonance frequency adjustment means for adjusting the frequency, transmission / reception circuit 14 for transmission / reception with the non-contact IC card 3 via the resonance circuit 12, and transmission power detection means for detecting transmission power in the transmission circuit 14 A transmission power detection circuit 15 as a control unit, a CPU (Central Processing Unit) 16 as a control means for performing overall control, and a transmission / reception circuit 14, a transmission power detection circuit 15 The power supply circuit 17 is configured to be supplied to the CPU 16.

  In the resonance circuit 12, the resonance frequency is switched and controlled by the frequency adjustment circuit 13 operated by the frequency control signals b0 and b1 supplied from the CPU 16, so that the communication characteristic with the non-contact IC card 3 is adjusted to the optimum value. The details will be described later.

  The CPU 16 is provided with a memory 18 such as a ROM or an EEPROM. In the memory 18, various threshold values are set and stored in advance, and various processing data are stored.

For example, as shown in FIG. 2, the resonance circuit 12 includes an antenna 11 and a tuning capacitor C0 connected in parallel to the antenna 11.
Further, for example, as shown in FIG. 2, the frequency adjustment circuit 13 includes a plurality (two in this example) of capacitors C1 to C2 connected in parallel to the tuning capacitor C0 and a plurality of capacitors C1 to C2. Each has a plurality of (two in this example) transistors T1 to T2 as switch means connected in series, and the plurality of transistors T1 to T2 are selectively turned on by frequency control signals b0 and b1 from the CPU 16. , Configured to be off-controlled.

  The plurality of capacitors C1 to C2 are for switching and setting the resonance frequency of the resonance circuit 12 to a desired value, and are set to different predetermined values (capacities), for example, values at which the resonance frequency changes at equal intervals. The desired capacitor (resonance frequency) is selected by switching the high and low frequency control signals b0 and b1 and selectively turning on and off the plurality of transistors T1 and T2. ing.

  The number of frequency control signals b0 and b1 and the plurality of capacitors is not limited to the above example, and may be larger. As the number increases, finer and more accurate frequency control becomes possible.

Next, the operation of the non-contact IC card reader / writer 1 according to the first embodiment in such a configuration will be described with reference to the flowchart shown in FIG.
When the CPU 14 of the non-contact IC card reader / writer 1 receives the adjustment mode start command transmitted from the host device 2, it selects (sets) the communication characteristic adjustment mode (step S1). Here, the adjustment mode start command may be transmitted once when the non-contact IC card reader / writer 1 is activated for the first time, or may be transmitted each time the non-contact IC card reader / writer 1 is turned on. Good.

  When entering the communication characteristic adjustment mode, the CPU 14 first radiates a carrier wave for adjustment from the antenna 11, detects transmission power in the transmission / reception circuit 14 at that time by the transmission power detection circuit 15, and stores it as transmission power data DAT1. 18 (step S2). Here, a threshold value of transmission power is stored in the memory 18 in advance, and it is determined whether or not the detected transmission power data DAT1 is equal to or greater than the threshold value (step S3). If the transmission power data DAT1 is greater than or equal to the threshold value as a result of this determination, the communication characteristic adjustment process is terminated assuming that the resonance frequency of the resonance circuit 12 has been adjusted to the optimum value.

  If the result of determination in step S3 is that the transmission power data DAT1 is less than or equal to the threshold value, the frequency adjustment circuit 13 increases the resonance frequency of the resonance circuit 12 by a certain value (step S4). Here, the transmission power in the transmission / reception circuit 14 after increasing the resonance frequency is detected by the transmission power detection circuit 15 and recorded in the memory 18 as transmission power data DAT2 (step S5).

  Next, the detected transmission power data DAT2 is compared with the threshold value of the transmission power stored in the memory 18 in advance (step S6). If the transmission power data DAT2 is equal to or greater than the threshold value, the resonance frequency of the resonance circuit 12 is the optimum value. As a result, the communication characteristic adjustment process is terminated.

  If the transmission power data DAT2 is equal to or smaller than the threshold value as a result of the comparison in step S6, the transmission power data DAT2 and DAT1 are compared (step S7). If the transmission power data DAT2 is greater than DAT1, the resonance frequency is the optimum value. After determining that it is shifted to a lower level and copying DAT2 to DAT1, the resonance frequency of the resonance circuit 12 is further increased by a constant value by the frequency adjustment circuit 13 (step S8). When the transmission power data DAT2 is smaller than DAT1, it is determined that the resonance frequency is shifted to a higher value than the optimum value, and after copying DAT2 to DAT1, the resonance frequency of the resonance circuit 12 is further increased by the frequency adjustment circuit 13 Decrease by a certain value (step S9).

  The transmission power in the transmission / reception circuit 14 after changing the resonance frequency in steps S8 and S9 is detected by the transmission power detection circuit 15 and recorded in the memory 18 as transmission power data DAT2 (steps S10 and S11). Next, it is determined whether or not the difference between the transmission power data DAT2 and DAT1 is equal to or larger than a predetermined value stored in the memory 18 in advance (steps S12 and S13), and the difference between DAT2 and DAT1 is equal to or larger than the predetermined value. In this case, the process returns to steps S8 and S9 and the same operation as described above is repeated.

  If the difference between DAT2 and DAT1 is not equal to or greater than the specified value as a result of the determination in steps S12 and S13, the transmission power data DAT2 and DAT1 are compared (steps S14 and S15). If DAT2 is smaller than DAT1, the resonance frequency is set. As a result of raising (or lowering), it may be considered that the optimum value has been exceeded and shifted in the direction opposite to the initial state.

  For example, when the frequency is initially shifted lower than the optimum value, the resonance frequency is increased, the difference between DAT2 and DAT1 is less than a specified value, and DAT2 is smaller than DAT1, the optimum value is set. The resonance frequency is returned to a lower value (step S16), and the communication characteristic adjustment process is terminated, assuming that it has jumped and shifted to the higher side.

  On the other hand, when the resonance frequency was lowered at the beginning, the resonance frequency was lowered further than the optimum value, and as a result, the resonance frequency was shifted to a lower value. The transmission power after changing the resonance frequency becomes lower. In this case, the resonance frequency is returned to a higher value (step S17), and the communication characteristic adjustment process is terminated.

  In steps S14 and S15, if DAT2 is greater than DAT1, it is determined that the resonance frequency has reached the optimum value, and the communication characteristic adjustment process is terminated.

  As described above, according to the first embodiment, the resonant frequency of the resonant circuit 12 is automatically adjusted so that the transmission power from the antenna 11 is equal to or higher than a specified threshold value, so that the installation environment and the built-in Regardless of the structure of the housing to be used, optimal communication characteristics can always be obtained.

Next, a second embodiment will be described.
FIG. 4 schematically shows a configuration of a non-contact IC card reader / writer as a wireless communication apparatus according to the second embodiment. The second embodiment is different from the first embodiment in that a magnetic sensor circuit 19 is added as a magnetic field strength detection unit that is installed on the antenna 11 and detects the magnetic field strength in the vicinity of the antenna 11. Is different. The output signal of the magnetic sensor circuit 19 is sent to the CPU 16. The power supply circuit 17 is different in that the power supply voltage supplied to the transmission / reception circuit 14 is controlled by a power supply circuit control signal supplied from the CPU 16. Therefore, the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

Next, the operation of the non-contact IC card reader / writer 1 according to the second embodiment in such a configuration will be described with reference to the flowcharts shown in FIGS.
When the CPU 14 of the non-contact IC card reader / writer 1 receives the adjustment mode start command transmitted from the host device 2, it selects (sets) the communication characteristic adjustment mode (step S1). Here, the adjustment mode start command may be transmitted once when the non-contact IC card reader / writer 1 is activated for the first time, or may be transmitted each time the non-contact IC card reader / writer 1 is turned on. Good.

  When entering the communication characteristic adjustment mode, the CPU 14 first radiates a carrier wave for adjustment from the antenna 11, detects transmission power in the transmission / reception circuit 14 at that time by the transmission power detection circuit 15, and stores it as transmission power data DAT1. 18 (step S2). Here, a threshold value of transmission power is stored in the memory 18 in advance, and it is determined whether or not the detected transmission power data DAT1 is equal to or greater than the threshold value (step S3). As a result of this determination, if the transmission power data DAT1 is equal to or greater than the threshold value, it is determined that the resonance frequency of the resonance circuit 12 is adjusted to the optimum value, and the frequency adjustment process is terminated, and the process proceeds to step S18.

  If the result of determination in step S3 is that the transmission power data DAT1 is less than or equal to the threshold value, the frequency adjustment circuit 13 increases the resonance frequency of the resonance circuit 12 by a certain value (step S4). Here, the transmission power in the transmission / reception circuit 14 after increasing the resonance frequency is detected by the transmission power detection circuit 15 and recorded in the memory 18 as transmission power data DAT2 (step S5).

  Next, the detected transmission power data DAT2 is compared with the threshold value of the transmission power stored in the memory 18 in advance (step S6). If the transmission power data DAT2 is equal to or greater than the threshold value, the resonance frequency of the resonance circuit 12 is the optimum value. As a result, the frequency adjustment process is terminated, and the process proceeds to step S18.

  If the transmission power data DAT2 is equal to or smaller than the threshold value as a result of the comparison in step S6, the transmission power data DAT2 and DAT1 are compared (step S7). If the transmission power data DAT2 is greater than DAT1, the resonance frequency is the optimum value. After determining that it is shifted to a lower level and copying DAT2 to DAT1, the resonance frequency of the resonance circuit 12 is further increased by a constant value by the frequency adjustment circuit 13 (step S8). When the transmission power data DAT2 is smaller than DAT1, it is determined that the resonance frequency is shifted to a higher value than the optimum value, and after copying DAT2 to DAT1, the resonance frequency of the resonance circuit 12 is further increased by the frequency adjustment circuit 13 Decrease by a certain value (step S9).

  The transmission power in the transmission / reception circuit 14 after changing the resonance frequency in steps S8 and S9 is detected by the transmission power detection circuit 15 and recorded in the memory 18 as transmission power data DAT2 (steps S10 and S11). Next, it is determined whether or not the difference between the transmission power data DAT2 and DAT1 is equal to or larger than a predetermined value stored in the memory 18 in advance (steps S12 and S13), and the difference between DAT2 and DAT1 is equal to or larger than the predetermined value. In this case, the process returns to steps S8 and S9 and the same operation as described above is repeated.

  If the difference between DAT2 and DAT1 is not equal to or greater than the specified value as a result of the determination in steps S12 and S13, the transmission power data DAT2 and DAT1 are compared (steps S14 and S15). If DAT2 is smaller than DAT1, the resonance frequency is set. As a result of raising (or lowering), it may be considered that the optimum value has been exceeded and shifted in the direction opposite to the initial state.

  For example, when the frequency is initially shifted lower than the optimum value, the resonance frequency is increased, the difference between DAT2 and DAT1 is less than a specified value, and DAT2 is smaller than DAT1, the optimum value is set. Assuming that the resonance frequency has jumped and shifted to a higher level, the resonance frequency is returned to a lower value (step S16), the frequency adjustment process is terminated, and the process proceeds to step S18.

  On the other hand, when the resonance frequency was lowered at the beginning, the resonance frequency was lowered further than the optimum value, and as a result, the resonance frequency was shifted to a lower value. The transmission power after changing the resonance frequency becomes lower. In this case, the resonance frequency is returned to a higher value (step S17), the frequency adjustment process is terminated, and the process proceeds to step S18.

  If DAT2 is greater than DAT1 in steps S14 and S15, it is determined that the resonance frequency has reached the optimum value, the frequency adjustment process is terminated, and the process proceeds to step S18.

  In step S18, the magnetic field strength near the antenna 11 is detected by the magnetic sensor circuit 19 installed on the antenna 11, and the detected value is sent to the CPU 16. The CPU 16 determines whether or not the magnetic field strength detected by the magnetic sensor circuit 19 is equal to or greater than a threshold value of the magnetic field strength stored in the memory 18 in advance (step S19), and when the detected magnetic field strength is equal to or greater than the threshold value. Assuming that a sufficiently strong magnetic field is generated from the antenna 11, the communication characteristic adjustment mode is terminated.

  As a result of the determination in step S19, if the detected magnetic field strength is not greater than or equal to the threshold value, the CPU 16 determines whether or not the power supply voltage supplied to the transmission / reception circuit 14 is a predetermined upper limit value (step S20). When the power supply voltage to the transmission / reception circuit 14 is the upper limit value, the communication characteristic adjustment mode is terminated.

  As a result of the determination in step S20, if the power supply voltage to the transmission / reception circuit 14 is not the upper limit value, the CPU 16 determines that the magnetic field strength from the antenna 11 is weakened by the surrounding environment or the like and supplies power to the power supply circuit 17. By transmitting the circuit control signal, the power supply voltage to the transmission / reception circuit 14 is increased by a certain value (step S21).

  Next, the CPU 16 detects the transmission power in the transmission / reception circuit 14 after increasing the power supply voltage to the transmission / reception circuit 14 in step S21 by the transmission power detection circuit 15 and records it in the memory 18 as transmission power data DAT2 ( Step S22), and then returning to step S18, the same operation as described above is repeated.

  As described above, after the power supply voltage to the transmission / reception circuit 14 is increased, the magnetic field strength near the antenna 11 is detected again by the magnetic sensor circuit 19, and the power supply to the transmission / reception circuit 14 is detected until the detected magnetic field strength is equal to or higher than the threshold value. Increase the voltage by a certain value. When the detected magnetic field strength in the vicinity of the antenna 11 becomes equal to or greater than the threshold value (step S19), the communication characteristic adjustment mode is terminated, assuming that a sufficient magnetic field is generated from the antenna 11.

  As described above, according to the second embodiment, the resonance frequency of the resonance circuit 12 is automatically adjusted so that the transmission power from the antenna 11 is equal to or higher than a specified threshold, and the magnetic field in the vicinity of the antenna 11 is also adjusted. The communication distance to the non-contact IC card 3 is adjusted by adjusting the power supply voltage to the transmission / reception circuit 14 so that the strength is equal to or higher than a prescribed threshold value, even though the resonance frequency is optimized by the structure of the housing to be incorporated. Even in the case where it is not possible to adjust, it is possible to obtain optimum communication characteristics by adjusting the supply voltage to the transmission / reception circuit 14.

  In the above embodiment, the case where the present invention is applied to a non-contact IC card reader / writer that transmits and receives data by wireless communication with a non-contact IC card driven by electric power induced by electromagnetic inductive coupling has been described. However, the present invention is not limited to this, and can be similarly applied to, for example, a non-contact IC tag reader / writer that transmits and receives data by wireless communication with a non-contact IC tag driven by electric power induced by electromagnetic inductive coupling.

1 is a block diagram schematically showing a configuration of a non-contact IC card reader / writer as a wireless communication apparatus according to a first embodiment of the present invention. The circuit diagram which shows roughly the specific structure of the resonance circuit and frequency adjustment circuit which concern on 1st Embodiment. The flowchart explaining operation | movement of the non-contact IC card reader / writer which concerns on 1st Embodiment. The block diagram which shows schematically the structure of the non-contact IC card reader / writer as a radio | wireless communication apparatus which concerns on the 2nd Embodiment of this invention. The flowchart explaining operation | movement of the non-contact IC card reader / writer based on 2nd Embodiment. The flowchart explaining operation | movement of the non-contact IC card reader / writer based on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Non-contact IC card reader / writer (wireless communication apparatus), 2 ... Host apparatus, 3 ... Non-contact IC card (wireless communication medium), 11 ... Antenna, 12 ... Resonance circuit, 13 ... Frequency adjustment circuit (Resonance frequency adjustment means) ), 14 ... Transmission / reception circuit, 15 ... Transmission power detection circuit (transmission power detection means), 16 ... CPU (control means), 17 ... Power supply circuit, 18 ... Memory (storage means), 19 ... Magnetic sensor circuit (magnetic field strength detection) means).

Claims (5)

A resonance circuit including an antenna for performing wireless communication using electromagnetic waves with a wireless communication medium is included, and data is transmitted and received by performing wireless communication with the wireless communication medium via the resonance circuit. In a wireless communication device,
A transceiver circuit for performing wireless communication using electromagnetic waves with a wireless communication medium via the resonance circuit;
When the communication characteristic adjustment mode is set, transmission power detection means for outputting an electromagnetic wave for adjustment from the antenna and detecting transmission power in the transmission circuit at that time,
Resonance frequency adjustment means for adjusting the resonance frequency of the resonance circuit so that the transmission power detected by the transmission power detection means is equal to or greater than a predetermined threshold;
A wireless communication apparatus comprising: A resonance circuit including an antenna for performing wireless communication using electromagnetic waves with a wireless communication medium is included, and data is transmitted and received by performing wireless communication with the wireless communication medium via the resonance circuit. In a wireless communication device,
A transceiver circuit for performing wireless communication using electromagnetic waves with a wireless communication medium via the resonance circuit;
When the communication characteristic adjustment mode is set, transmission power detection means for outputting an electromagnetic wave for adjustment from the antenna and detecting transmission power in the transmission circuit at that time,
Resonance frequency adjustment means for adjusting the resonance frequency of the resonance circuit so that the transmission power detected by the transmission power detection means is equal to or greater than a predetermined threshold;
When the adjustment of the resonance frequency of the resonance circuit by the resonance frequency adjustment means is completed, the magnetic field strength detection means for detecting the magnetic field strength in the vicinity of the antenna;
Power supply voltage adjusting means for adjusting the power supply voltage to the transmission / reception circuit so that the magnetic field strength detected by the magnetic field strength detection means is equal to or greater than a predetermined threshold;
A wireless communication apparatus comprising:   The wireless communication device according to claim 1 or 2, wherein the communication characteristic adjustment mode is set by receiving an adjustment mode start command transmitted from a host device of the wireless communication device.   4. The wireless communication apparatus according to claim 3, wherein the adjustment mode start command is transmitted once when the wireless communication apparatus is activated for the first time, or is transmitted each time the wireless communication apparatus is powered on.   6. The wireless communication apparatus according to claim 4, wherein the wireless communication medium is a contactless IC card driven by electric power induced by electromagnetic inductive coupling.

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