JP5185789B2 - Wireless communication device - Google Patents

Description

  The present invention relates to a wireless communication apparatus capable of adjusting a resonance frequency of a loop antenna.

  In recent years, proximity wireless communication using RFID (Radio Frequency Identification), which is a non-contact IC chip, has been used for various purposes, and is used for settlement of electronic money, commuter pass, etc. . As mobile terminals such as mobile phones, PHS, and PDAs have become more sophisticated, RFIDs are often mounted on these mobile terminals.

  A passive RFID built in a card or the like operates by generating an electromotive force in a loop antenna by a magnetic field generated by a reader, and performs communication using the electromagnetic wave as a signal. On the other hand, in a mobile terminal, an active RFID is mounted from the viewpoint of having a battery and security. By adopting an active type using a power supply, more processing can be performed, so that a plurality of services can be switched and used, or a communicable distance can be extended. Further, security is improved by applying a security lock to the RFID on the main body side of the mobile terminal and supplying power to the IC chip only when the lock is released.

  However, even a portable terminal equipped with an active RFID has a configuration in which power is supplied to the IC chip only when an electromotive force is detected in the loop antenna in order to reduce power consumption. Therefore, matching the resonance frequency of the loop antenna with the carrier wave (13.56 MHz) is as important as the passive type.

The resonance frequency is basically determined by the length of the antenna, but it is affected by the inductance of the circuit connected to the antenna, or the antenna's inductance changes due to the proximity of metal. You may not get. Patent Document 1 includes a configuration in which a resonance frequency (tuning frequency) is maintained regardless of ambient conditions by providing a capacitor or an additional coil on an antenna and switching the capacitor, or by providing a tap on the additional coil to switch an effective length. Has been proposed.
JP2001-344574

  In the above-mentioned Patent Document 1, it is assumed that a capacitor or a coil tap can be switched using a rotary switch or a semiconductor switch. A semiconductor switch is considered to mean a transistor. Patent Document 1 exemplifies a circuit in which a transistor is placed between an antenna and a capacitor and the transistor and the capacitor are turned on by turning on the transistor.

  However, if a transistor is disposed between the antenna and the capacitor, the circuit design becomes difficult because the ON resistance and inductance of the transistor must be taken into consideration. Therefore, the transistor is preferably arranged on the ground side with respect to the capacitor.

  By the way, since a parasitic diode is formed inside a transistor (hereinafter referred to as an n-type MOSFET as an example), a current flowing through the ground line reaches a capacitor (a current flows from the source to the drain). ). For this reason, there is a possibility that common mode noise flowing in the ground line enters the capacitor and noise is added to the signal. Also, if the input voltage to the gate is higher than between the drain and source, latch-up may occur and the FET may remain on. Therefore, it is necessary to connect a pull-up power supply to the drain of the transistor and increase the voltage on the drain side.

  When the transistor is OFF, the current from the pull-up power supply does not flow, and the voltage on the drain side of the transistor becomes the same potential as the voltage of the pull-up power supply. However, when the transistor is turned on, a leakage current flows from the pull-up power source to the ground through the transistor. Although this leakage current can be reduced by increasing the resistance value of the pull-up resistor, there is no change in that the battery power is wasted, and the operating time of the mobile terminal is unnecessarily shortened. It was a factor.

  Accordingly, an object of the present invention is to reduce power consumption while enabling the resonance frequency of a loop antenna to be adjusted in a wireless communication apparatus that performs magnetic field communication using a loop antenna.

  In order to solve the above problems, a typical configuration of a wireless communication apparatus according to the present invention includes a loop antenna for magnetic field communication, at least one adjusting unit for adjusting a resonance frequency of the loop antenna, and a circuit for the adjusting unit. FET to be connected to or disconnected from, a pull-up power source connected between the FET and the adjusting means, a storage unit for storing information on whether the adjusting means is valid or invalid, and switching for controlling ON / OFF of the FET A control unit and a communication detection unit that detects that magnetic field communication is being performed. The switching control unit is effective in adjusting means with reference to the storage unit, and magnetic field communication with reference to the communication detection unit. In the case where the adjustment is performed, the FET is turned on to enable the adjustment means.

  Further, another typical configuration of the wireless communication apparatus according to the present invention includes a loop antenna for magnetic field communication, at least one adjustment unit that adjusts the resonance frequency of the loop antenna, and the adjustment unit connected to the circuit. An FET to be disconnected, a pull-up power source connected between the FET and the adjusting unit, a storage unit that stores information on whether the adjusting unit is valid or invalid, a switching control unit that controls ON / OFF of the pull-up power source, A communication detection unit that detects that magnetic field communication is being performed, and the switching control unit is effective with reference to the storage unit, and the magnetic field communication is performed with reference to the communication detection unit. In this case, the adjustment means is enabled by turning on the pull-up power supply.

  A magnetic field communication unit that performs magnetic field communication using a loop antenna, a main control unit that exchanges information with the magnetic field communication unit, and a power supply unit that supplies power to the magnetic field communication unit and the main control unit are provided independently. Also good.

  The storage unit is preferably a non-volatile memory and can be updated from the main control unit.

  Further, a plurality of adjusting means are provided, and valid or invalid information for each of the plural adjusting means is stored in the storage unit, and the switching control unit may refer to the storage unit and switch between valid or invalid for each adjusting unit. .

  The storage unit further stores use permission / inhibition information indicating whether or not the use of the magnetic field communication unit is permitted, and the switching control unit refers to the storage unit and the adjustment means is effective, and the use permission / inhibition information is permitted. It is preferable to make the adjustment means effective when the magnetic field communication is performed with reference to the communication detection unit.

  According to the present invention, in a wireless communication apparatus that performs magnetic field communication using a loop antenna, the power consumption can be reduced while the resonance frequency of the loop antenna can be adjusted.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  In the following embodiments, a mobile phone will be described as an example of a mobile terminal. However, the portable terminal according to the present invention can be applied as long as the apparatus is driven by a battery and has portability. For example, the portable terminal is provided in a PHS (Personal Handy-pone System) terminal, a personal computer, a notebook personal computer, or the like. Various devices that can acquire e-mail such as expansion devices to be installed in PCMCIA slot or USB (Universal Serial Bus), PDA (Personal Digital Assistant), digital camera, music player, car navigation, portable TV, game device, DVD player, remote controller Electronic devices.

[First Embodiment]
FIG. 1 is a functional block diagram illustrating a schematic configuration of a mobile terminal according to the first embodiment, and FIG. 2 is a diagram illustrating a configuration of a storage unit. The mobile terminal 10 includes a main body function unit 100 and an RFID unit 200. The main body function unit 100 and the RFID unit 200 operate with power supplied individually from the same battery 12 as described later.

  The main body function unit 100 includes a main control unit 110, a main power supply unit 112, a memory 120, a display unit 122, an operation unit 124, an audio input unit 126, an audio output unit 128, and a wireless communication unit 130. Consists of including.

  First, the main body function unit 100 will be described. The main control unit 110 manages and controls the entire portable terminal 110 by a semiconductor integrated circuit including a central processing unit (CPU), and uses a program stored in the memory 120 to make a call function, a mail transmission / reception function, an imaging function, It also performs music playback and TV viewing functions. In addition, information can be exchanged with the magnetic field communication unit 210, and predetermined processing using magnetic field communication such as electronic money or payment can be performed.

  The main power supply unit 112 adjusts the power supplied from the battery 12 to a predetermined voltage and supplies it to the main body function unit 100 including the main control unit 110. The main power supply unit 112 does not supply power to the RFID unit 200. The main power supply unit 112 includes, for example, a capacitor that temporarily accumulates electric charge, a regulator that generates a predetermined voltage, and the like.

  The memory 120 includes a ROM, a RAM, an EEPROM, a nonvolatile RAM, a flash memory, an HDD, and the like, and stores a program processed by the main control unit 110. In the present embodiment, the memory 120 also functions as the access point storage unit 132.

  The display unit 122 is configured by a liquid crystal display, an EL (Electro Luminescence) display, and the like, and displays a telephone number of a caller or a caller or a GUI (Graphical User Interface) of an application such as a mailer or a browser.

  The operation unit 124 includes a switch such as a keyboard, a cross key, and a joystick, and accepts a user operation input. The voice input unit 126 includes voice conversion means such as a microphone, and converts a user voice input during a call into an electrical signal that can be processed in the mobile terminal 10. The voice output unit 128 is configured by a speaker, and converts the voice signal of the call partner received by the mobile terminal 10 into voice and outputs the voice. The voice output unit 128 can also output a ring tone, an operation confirmation sound of the operation unit 124, an alarm sound, and the like.

  For example, the wireless communication unit 130 establishes wireless communication with a base station through a wireless communication method based on a CDMA (Code Division Multiple Access) method, and performs data communication such as voice communication with a communication partner and acquisition of Web information. To do.

  The RFID unit 200 includes a loop antenna 202, a magnetic field communication unit 210, an RFID power supply unit 212, a communication detection unit 214, a storage unit 216, a capacitor 218 as an example of an adjustment unit, an FET 220, and a switching control unit 222. And a pull-up power source 224.

  The loop antenna 202 is an annular antenna for magnetic field communication, generates an electromotive force by a magnetic field emitted from a reader (not shown), and transmits the current to the magnetic field communication unit 210 as a signal. The magnetic field communication unit 210 can be configured to include a non-contact IC chip, and processes information communicated by the loop antenna 202.

  The RFID power supply unit 212 adjusts the power supplied from the battery 12 to a predetermined voltage and supplies it to the RFID unit 200 including the magnetic field communication unit 210. The RFID power supply unit 212 can be turned on / off from the main control unit 110. The RFID power supply unit 212 does not supply power to the main body function unit 100. The RFID power supply unit 212 includes, for example, a capacitor that temporarily accumulates electric charge, a regulator that generates a predetermined voltage, and the like.

  By providing the RFID power supply unit 212 of the RFID unit 200 separately from the main power supply unit 112 of the main body function unit 100, power supply to the magnetic field communication unit 210 can be individually controlled. Therefore, for example, when the magnetic field communication unit 210 is not used, the supply of power to this can be stopped. Thereby, even in the portable terminal 10 equipped with the function of performing magnetic field communication, the power consumption can be reliably reduced when the function is not used.

  The communication detection unit 214 detects an electromotive force generated in the loop antenna 202 and detects whether or not magnetic field communication is being performed. Further, in addition to the electromotive force, it may be determined that the magnetic field communication is started when the carrier wave of the magnetic field communication is further detected. If the communication detection unit 214 detects that magnetic field communication has been started, the communication detection unit 214 notifies the magnetic field communication unit 210 to that effect.

  As illustrated in FIG. 2A, the storage unit 216 stores information on whether the capacitor 218 described later is valid or invalid. When a plurality of capacitors 218 are installed, valid or invalid information is stored for each capacitor 218. These pieces of information can be converted into information by setting a flag with bits. The storage unit 216 includes a non-volatile memory, and can hold information on whether the adjustment unit is valid or invalid even when the power is turned off. Information stored in the storage unit 216 can be updated from the main control unit 110 of the main body function unit 100.

  Further, as shown in FIG. 2B, the storage unit 216 can further store use permission / prohibition information of the RFID unit 200. The usage permission / prohibition information may be permitted or disallowed information by setting a flag with a bit, for example. The use permission / prohibition information is for security purposes. When the user permits the use of the RFID unit 200 by operating the operation unit 124 in the main body function unit 100, the main control unit 110 temporarily stores the information in the storage unit 216. Write permission information, and then write impossible information again after a predetermined time. As a result, magnetic field communication will not be performed unless authorized by the user, so it is possible to prevent information from being read or settled if lost, etc., improving the security of mobile devices Can be made.

  The capacitor 218 (adjusting means) adjusts the resonance frequency by enabling the connection with the loop antenna 202. Examples of the adjusting means include a coil and an additional antenna in addition to the capacitor. The number of capacitors 218 may be one, but in the present embodiment, a plurality of capacitors 218 are attached in parallel to the loop antenna 202. When a plurality of capacitors 218 are attached, they may have the same capacity or different capacities. As a result, it is possible to switch to capacitors 218 having different values, or to increase or decrease the number of effective capacitors 218, and to appropriately adjust the resonance frequency of the loop antenna 202.

  The FET 220 is provided for each capacitor 218. When the FET 220 is turned ON, the capacitor 218 is connected to the circuit to be enabled, and when it is turned OFF, the FET 220 is disconnected from the circuit to be disabled. In the present embodiment, the FET 220 is disposed between the capacitor 218 and the ground.

  The switching control unit 222 (port controller) applies a voltage to the gate of the FET 220 and controls its ON / OFF. The switching control unit 222 includes a plurality of output terminals. When a plurality of capacitors 218 are installed, the switching control unit 222 can be individually connected and individually ON / OFF controlled.

  The pull-up power source 224 includes a regulator 226 that generates a predetermined voltage and a pull-up resistor 228. One end of the pull-up resistor 228 is connected to the output of the regulator 226, and the other end is connected between the FET 220 and the capacitor 218. As a result, while the FET 220 is OFF, the potential of the drain (capacitor 218 side) of the FET 220 becomes equal to the potential of the pull-up power supply, and noise from the ground line due to the parasitic diode and latch-up of the FET 220 can be prevented. it can.

  Next, a characteristic operation in the present embodiment will be described. FIG. 3 is a flowchart for explaining the operation of the switching control unit 222. FIG. 3 (a) is an example of basic operation, and FIG. 3 (b) is an example of further considering use permission information.

  FIG. 3A shows the operation when the valid / invalid information of the capacitor 218 is stored in the storage unit 216 as shown in FIG. First, it is assumed that all FETs 220 are OFF in a state where magnetic field communication is not performed. When the communication detection unit 214 detects that the magnetic field communication is started (S310), the communication detection unit 214 notifies the magnetic field communication unit 210 to that effect (S312). The magnetic field communication unit 210 notifies the switching control unit 222 of the start of communication (S314). The switching control unit 222 reads valid / invalid information of the capacitor 218 with reference to the storage unit 216 (S318). When there are a plurality of capacitors 218, information is read for each capacitor 218.

  Then, the switching control unit 222 determines validity / invalidity for a certain capacitor 218 (S320), and if it is stored as valid, turns on the corresponding FET 220 (S322). Thereby, the capacitor 218 is connected to the circuit and becomes effective, and the resonance frequency of the loop antenna can be changed. That is, as shown in FIG. 2A, the FET 220 is turned on to enable the capacitor 218 only when the capacitor 218 (adjusting means) is effective and magnetic field communication is performed.

  If all the capacitors 218 have not been processed (S324), information is read for the next capacitor 218 (returns to S318). When the processing is completed for all the capacitors 218 (S324), the magnetic field communication unit 210 performs magnetic field communication (S326). When the communication is completed, the magnetic field communication unit 210 notifies the switching control unit 222 (S328), and the switching control unit 222 turns off all the FETs 220 (S330).

  According to the above configuration, the FET 220 can be turned on only during magnetic field communication. Therefore, while the magnetic field communication is not performed, a leakage current does not flow from the pull-up power source 224 via the FET 220, and the amount of wasted power can be kept to a minimum. As a result, while allowing the resonance frequency of the loop antenna 202 to be adjusted, the time during which the leak current flows can be made extremely short.

  FIG. 3B shows the operation when the use permission / prohibition information of the RFID unit 200 is further stored in the storage unit 216 as shown in FIG. Only a portion different from the flowchart of FIG. 3A will be described.

  When the switching control unit 222 is notified of the start of communication from the magnetic field communication unit 210 (S314), the switching control unit 222 reads the usage permission / prohibition information with reference to the storage unit (S316). If the use permission / prohibition information is “impossible”, the process ends as it is (S317). When the usage permission information is “permitted”, the information on the validity or invalidity of the capacitor 218 is read, and the FET 220 corresponding to the valid capacitor 218 is turned on (S318 to S324).

  That is, as shown in FIG. 2B, the capacitor 218 is valid with reference to the storage unit 216, usage permission information is permitted, and magnetic field communication is performed with reference to the communication detection unit 214. Only in this case is the capacitor 218 enabled. Thereby, in addition to reducing the leakage current, security can be enhanced.

[Second Embodiment]
A second embodiment of the mobile terminal according to the present invention will be described. FIG. 4 is a functional block diagram illustrating a schematic configuration of the mobile terminal according to the second embodiment. The same parts as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

  In the first embodiment, it has been described that when the adjusting means (capacitor 218) is effective and magnetic field communication is performed, the FET is turned on to enable the adjusting means. On the other hand, the second embodiment is configured to turn on the pull-up power source 224 only when conditions are met.

  As shown in FIG. 4, a pull-up power source switch 230 is provided between the regulator 226 and the pull-up resistor 228. When a plurality of capacitors 218 are installed, a switch 230 is installed for each. The switch 230 can be composed of a semiconductor switch such as an FET or a bipolar transistor.

  The switching control unit 222 has one of the output terminals connected to the gate of the switch 230, and can dynamically control ON / OFF of the switch 230.

  FIG. 5 is a flowchart for explaining the operation of the switching control unit 222 according to the second embodiment. The switching control unit 222 determines whether the capacitor 218 is valid / invalid (S320), and if it is stored as valid, the corresponding switch 230 is turned on (S340). In other words, the switching control unit 222 refers to the pull-up power supply 224 only when the capacitor 218 (adjustment unit) is valid with reference to the storage unit 216 and magnetic field communication is performed with reference to the communication detection unit 214. Turn on to enable capacitor 218. As a result, a pull-up power supply is connected to the ground side of the capacitor 218, and noise from the ground through the parasitic diode is cut off, and a signal can be appropriately obtained from the loop antenna 202.

  Accordingly, it is an object to reduce the power consumption by making it possible to adjust the resonance frequency of the loop antenna to a very short time while allowing the leakage current to flow.

  In the configuration of the second embodiment, when the magnetic field communication is not performed, the pull-up power supply is stopped, so that leakage current can be prevented even when the FET 220 is kept on. However, since the voltage at the gate is higher than the drain of the FET 220 and a latch-up phenomenon may occur, it is preferable that the FET 220 is also turned on / off together with the switch 230.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention can be used as a wireless communication device capable of adjusting the resonance frequency of a loop antenna.

It is a functional block diagram explaining the schematic structure of the portable terminal which concerns on 1st Embodiment. It is a figure explaining the structure of a memory | storage part. It is a flowchart explaining operation | movement of the switching control part which concerns on 1st Embodiment. It is a functional block diagram explaining schematic structure of the portable terminal which concerns on 2nd Embodiment. It is a flowchart explaining operation | movement of the switching control part which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Portable terminal, 100 ... Main body function part, 110 ... Main control part, 112 ... Main power supply part, 12 ... Battery, 120 ... Memory, 122 ... Display part, 124 ... Operation part, 126 ... Voice input part, 128 ... Voice Output unit, 130 ... wireless communication unit, 200 ... RFID unit, 202 ... loop antenna, 210 ... magnetic field communication unit, 212 ... RFID power supply unit, 214 ... communication detection unit, 216 ... storage unit, 218 ... capacitor, 220 ... FET, 222: switching control unit, 224 ... pull-up power supply, 226 ... regulator, 228 ... pull-up resistor, 230 ... switch

Claims (6)

A loop antenna for magnetic field communication;
At least one adjusting means for adjusting the resonance frequency of the loop antenna;
FET for connecting or disconnecting the adjusting means to the circuit;
A pull-up power supply connected between the FET and the adjusting means;
A storage unit for storing valid or invalid information of the adjusting means;
A switching control unit for controlling ON / OFF of the FET;
A communication detection unit that detects that magnetic field communication is being performed,
The switching control unit turns on the FET to turn on the adjusting unit when the adjusting unit is effective with reference to the storage unit and magnetic field communication is performed with reference to the communication detecting unit. A wireless communication device that is enabled. A loop antenna for magnetic field communication;
At least one adjusting means for adjusting the resonance frequency of the loop antenna;
FET for connecting or disconnecting the adjusting means to the circuit;
A pull-up power supply connected between the FET and the adjusting means;
A storage unit for storing valid or invalid information of the adjusting means;
A switching control unit for controlling ON / OFF of the pull-up power supply;
A communication detection unit that detects that magnetic field communication is being performed,
The switching control unit turns on the pull-up power supply when the adjustment unit is effective with reference to the storage unit and magnetic field communication is performed with reference to the communication detection unit. A wireless communication apparatus characterized by enabling means. A magnetic field communication unit for performing magnetic field communication by the loop antenna;
A main control unit for exchanging information with the magnetic field communication unit;
The wireless communication apparatus according to claim 1, further comprising a power supply unit that supplies power to the magnetic field communication unit and the main control unit.   The wireless communication apparatus according to claim 3, wherein the storage unit is a nonvolatile memory and can be updated from the main control unit. A plurality of adjustment means are provided, and the storage unit stores valid or invalid information for each of the plurality of adjustment means,
The wireless communication device according to claim 1, wherein the switching control unit switches between valid and invalid for each of the adjustment units with reference to the storage unit. The storage unit further stores use permission / rejection information indicating whether or not use of the magnetic field communication unit is permitted,
When the switching control unit is effective with reference to the storage unit, the use permission information is permitted, and magnetic field communication is performed with reference to the communication detection unit, The wireless communication apparatus according to claim 1, wherein the adjustment unit is enabled.

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