JP2009153023A - Antenna apparatus and personal digital assistant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna apparatus and a personal digital assistant capable of setting an optimal reactance value to each function without enlarging an antenna area in an RFID (radio frequency identification) antenna configuration including a card function and a reader/writer function. <P>SOLUTION: The antenna apparatus comprises one loop antenna 11 as an RFID antenna element, and in the middle of the loop antenna 11, a tap 12 is provided. A receiving circuit 16 of a card function and a reader/writer function and a transmission circuit 17 of the card function are connected to one terminal A of the loop antenna 11. The transmission circuit 18 of the reader/writer function is connected to the terminal B of the tap 12 in the middle of the loop antenna 11 via a switch 14 so as to be disconnected from the loop antenna 11. The loop antenna 11 is used in the card function as a whole, and a part of the loop antenna 11 to the intermediate tap 12 is used in transmission of the reader/writer function. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an antenna device and a portable information terminal used in an RFID system.

  Uses so-called RFID (Radio Frequency Identification), which reads and writes information to and from an IC chip mounted on a card-like medium or a portable information terminal by wireless communication using non-contact communication such as proximity communication and short-range communication. Various systems have been proposed and put into practical use. As an example of RFID, Felica (registered), which has antennas and IC chips mounted on card-like media and portable information terminals, enables entry and exit of transportation facilities such as station ticket gates, fee settlement, and payment of various fees at cash registers, etc. Trademark) is widespread.

  This type of RFID has a card function that functions as a medium side that holds information (passive RFID), and a reader / writer (R / W) side that performs information reading and writing on this medium (active RFID). It has a functioning reader / writer. The card function is a function that communicates with a reader / writer installed in a ticket gate of a station, a cash register of a store, etc., and mainly writes and reads data from the reader / writer, and reception is a main passive function. On the other hand, the reader / writer function itself becomes a reader / writer, communicates with other RFIDs (passive RFIDs such as other terminals and poster-embedded IC chips), and mainly writes data to and reads data from other RFIDs. Function, transmission is the main active function.

  Some RFIDs mounted on portable information terminals such as cellular phones have both the card function and the reader / writer function. An antenna such as a loop antenna provided in an RFID has an optimum reactance value of the antenna for each function of a passive card function and an active reader / writer function. As described above, in an RFID having two functions, it is necessary to provide an antenna corresponding to each function. Conventionally, since a loop antenna having a large opening area is used, the reactance value is optimized for each function. Even without them, the required specifications (performance and specifications such as transmission characteristics and reception characteristics) could be satisfied.

  FIG. 5 is a diagram showing a first example of a conventional antenna device used for an RFID having two functions. The antenna device of the first example is a configuration example of a single antenna system, and includes one loop antenna 51. This antenna device forms a resonance circuit with a loop antenna 51 and a capacitor 53, and is connected to an RFID unit 55 composed of an IC chip or the like, and transmits a transmission signal and a reception signal to another reader / writer, RFID, and RFID unit 55. Communicate between. In this case, a signal is transmitted through a circuit and a terminal corresponding to each of the operations of receiving the card function and the reader / writer function, transmitting the card function, and transmitting the reader / writer function. In other words, the single loop antenna 51 having the inductance value L51 corresponds to the two functions of the card function and the reader / writer function. In this configuration, the antenna device does not have an optimum reactance value in both the card function and the reader / writer function, but by increasing the opening area of the loop antenna, the specifications required for each function may be satisfied. it can.

  FIG. 6 is a diagram showing a second example of a conventional antenna device used for an RFID having two functions. The antenna device of the second example is a configuration example of a two-antenna system, and includes two loop antennas 61 and 62 that are M-coupled to each other. This antenna device forms a resonance circuit by loop antennas 61 and 62 and a capacitor 63, and is connected to an RFID unit 55 formed of an IC chip or the like, and transmits a transmission signal and a reception signal to other reader / writers or RFID and RFID units. Exchange with 55. In the second example, the loop antenna 61 having the inductance value L61 corresponds to the reception of the card function and the reader / writer function and the transmission of the card function. In addition, the loop antenna 62 having the inductance value L62 corresponds to transmission of the reader / writer function. That is, two loop antennas 61 and 62 are provided for each function.

In addition, as a method of switching the resonance frequency of the antenna device to cope with a plurality of frequencies, a method of switching a capacitor (for example, see Patent Document 1), a method of switching an inductor (for example, see Patent Document 2), and the like are known. .
JP 2001-344574 A JP 2001-067447 A

  Recently, the size of the device has been reduced, and when an RFID is mounted on a portable information terminal or the like, the opening area of the antenna has been reduced due to space restrictions. As in the first example of the conventional example described above, when one loop antenna supports two functions, if the antenna has a large opening area, a predetermined specification can be obtained even if there is a slight deviation from the optimum reactance value for each function. It is possible to be satisfied. However, if the aperture area of the antenna is reduced as the device is reduced in size, a single loop antenna may fail to ensure sufficient performance by satisfying predetermined specifications in each function.

  On the other hand, when a loop antenna is provided for each function as in the second example of the conventional example, it is possible to set an optimum reactance value for each function. However, this configuration requires two antennas, which requires a large installation area, and thus cannot be adapted to downsizing of the apparatus. Further, one loop antenna 62 may adversely affect the other loop antenna 61, and the characteristics of the loop antenna tend to be deteriorated.

  The present invention has been made in view of the above circumstances, and can be adapted to downsizing of the apparatus without increasing the antenna area when both the RFID card function and the reader / writer function are supported. An object of the present invention is to provide an antenna device and a portable information terminal that can set an optimum reactance value.

An antenna device of the present invention is an antenna device that can handle a card function and a reader / writer function in RFID, and is a first loop having a first reactance value and a part of the first loop. A second loop having a second reactance value smaller than the first reactance value, and the first loop is used for transmission / reception of the card function and reception of the reader / writer function, The second loop is used for transmission of the reader / writer function.
With the above configuration, when both the RFID card function and the reader / writer function are supported, it is possible to realize an optimum reactance value for each function without increasing the antenna area. For this reason, it is possible to satisfy the required performance in each function while being adaptable to downsizing of the apparatus.

Further, the present invention is the antenna device described above, wherein the card function is a function of receiving radio waves from another reader / writer or RFID and reading data by others, and the reader / writer function is other functions. This includes the function of transmitting radio waves to RFID and reading data from others.
With the above configuration, it is possible to realize optimum reactance values for both the card function mainly for reception and the reader / writer function mainly for transmission.

Further, the present invention is the above antenna device, wherein one end of the first loop is connected to the card function and the reader / writer function receiving circuit, and the card function transmitting circuit, One end of the second loop in the middle of the loop includes one connected to the transmitter circuit of the reader / writer function.
With the above configuration, the first loop having the first reactance value is functioned and used in reception of the card function and the reader / writer function and transmission of the card function, and a part of the first loop is transmitted in the transmission of the reader / writer function. When the second loop having the second reactance value is used as a function, the optimum reactance value for each function can be realized and operated.

In addition, the present invention includes the antenna device described above, wherein the second reactance value is approximately half of the first reactance value.
With the above configuration, the second reactance value can be set with a simple configuration, and an optimum inductance value can be realized for each of the card function and the reader / writer function.

Further, the present invention is the antenna device described above, wherein the first loop and the second loop are formed by a coiled loop antenna wound, and the second loop is the first loop. Including those with fewer turns.
With the above configuration, the first loop and the second loop can be configured with a small area by the coiled loop antenna.

Further, the present invention includes the antenna device described above, wherein the number of turns of the second loop is approximately half the number of turns of the first loop.
With the above configuration, the second reactance value can be set with a simple configuration and a small area in the loop antenna, and an optimum inductance value can be realized for each of the card function and the reader / writer function. For example, by setting the number of turns of the second loop to an integer, the terminal of the second loop can be easily installed, and a smaller antenna device can be configured.

Further, the present invention provides the antenna device as described above, wherein a signal line between one end of the second loop in the middle of the first loop and a transmission circuit of the reader / writer function is connected to the card function. And a switch having a switch for disconnecting the second loop from the reader / writer function transmission circuit during operation.
With the above configuration, when the card function is operated, the switch is turned off to separate the second loop from the reader / writer function transmission circuit, thereby preventing an excessive input from being input to the signal line during the reader / writer function operation. It is possible.

Moreover, this invention provides a portable information terminal provided with the antenna apparatus in any one of the above.
With the above configuration, it is equipped with an antenna device that can set an optimum reactance value for each function of the card function and the reader / writer function without increasing the antenna area, and can be adapted to downsizing of the device, and In addition, it is possible to realize a portable information terminal including an RFID that satisfies the performance required for each of the card function and the reader / writer function.

  According to the present invention, when both the RFID card function and the reader / writer function are supported, it is possible to adapt to the downsizing of the apparatus without increasing the antenna area and to obtain an optimum reactance value for each function. An antenna device and a portable information terminal that can be set can be provided.

(First embodiment)
In this embodiment, a configuration example of an RFID antenna device mounted on a portable information terminal such as a cellular phone is shown. The RFID according to the present embodiment is applied to Felica (registered trademark) or the like, and has a card function mainly including a passive function that functions as a medium side (passive RFID) that holds information, and the medium. It is assumed that an active function that functions as a reader / writer (R / W) side (active RFID) that reads and writes information has a reader / writer function mainly.

  FIG. 1 is a diagram showing a schematic configuration of an antenna apparatus according to the first embodiment of the present invention. The antenna device of the present embodiment includes one loop antenna 11 as an antenna element for RFID, and this loop antenna 11 has a tap 12 in the middle as an intermediate terminal. A capacitor 13 having a capacitance C1 is connected to both ends of the loop antenna 11, and a resonance circuit composed of the loop antenna 11 and the capacitor 13 is connected to an RFID unit 15 such as an IC chip including a memory, a transmission / reception circuit, and the like. Yes.

  A terminal A extending from one end of the loop antenna 11 is connected to a receiving circuit 16 having a card function and a reader / writer function and a transmitting circuit 17 having a card function in the RFID unit 15. A transmission circuit 18 having a reader / writer function in the RFID unit 15 is detachably connected to a terminal B extending from a tap 12 in the middle of the loop antenna 11 via a switch 14. A terminal C extending from the other end of the loop antenna 11 is grounded via a capacitor and connected to the RFID unit 15.

  The antenna device of the present embodiment can be used in a state where the tap 12 is pulled out from the middle of one loop antenna 11 and the loop antenna 11 is set to an optimum reactance value for each of the card function and the reader / writer function. In the transmission / reception of the card function and the reception of the reader / writer function, the entire loop antenna 11 is used as the first loop, and the entire antenna is caused to function by the inductance value L1 corresponding to the first reactance value. In the transmission of the reader / writer function, a part up to the tap 12 of the loop antenna 11 is used as the second loop, and a part of the antenna is caused to function by the inductance value L2 corresponding to the second reactance value. Thereby, an optimum reactance value is realized in each of the card function and the reader / writer function. At this time, the inductance value L2 is smaller than the inductance value L1.

  Further, a switch 14 is provided in the middle of a reader / writer function transmission line (a signal line of a transmission signal when the reader / writer function is operated) for connecting the tap 12 of the loop antenna 11 and the reader / writer function transmission circuit 18 to operate the card function. At this time (when the reader / writer function is not transmitted), the switch 14 is opened and the loop antenna 11 and the transmission circuit 18 are disconnected. Thereby, when receiving the card function, it is possible to prevent an excessive input from being input to the transmission line of the reader / writer function or the transmission circuit 18.

  FIG. 2 is a diagram illustrating a configuration example of the loop antenna according to the present embodiment. The loop antenna 11 is a coiled antenna formed by winding a plurality of conductors in a substantially rectangular shape. Corresponding to FIG. 1, both ends of the loop antenna 11 are terminals A and C, and an intermediate terminal extending from the tap 12 is a terminal B. In this configuration, the terminal A is connected to the card function / reader / writer function receiving circuit 16 and the card function transmitting circuit 17, and the terminal B is connected to the reader / writer function transmitting circuit 18 via the switch 14. The terminal C is grounded via a capacitor and connected to the RFID unit 15.

  In the configuration example of FIG. 2, the coiled loop antenna 11 has a total number of turns of 4 turns from the terminal C to the terminal A, a tap 12 is provided at a substantially midpoint, and a tap is formed from one end of the loop antenna 11. Up to 12 (from terminal C to terminal B) is the number of turns of 2 turns.

  Here, the relationship of the reactance value (determined by the number of turns N or the inductance value L) of the loop antenna 11 is as shown in FIG. The reactance value XL of the coiled loop antenna 11 is determined by the inductance value L (mH) of this coil. In the example of FIG. 3, the entire loop antenna 11 is configured with 4 turns with an inductance value L1, and a part of the loop antenna 11 up to the tap 12 is configured with 2 turns with an inductance value L2. In this case, the inductance value L1 is optimal for reception of the card function and the reader / writer function, the inductance value L1 is optimal for transmission of the card function, and the inductance value L2 is optimal for transmission of the reader / writer function.

  Next, a setting example of the inductance value L and the number of turns N of the loop antenna 11 applied to this embodiment will be shown. When the RFID antenna is used for both the card function and the reader / writer function, assuming that the inductance value is L1 in the case of the card function (reception main) and the inductance value is L2 in the case of the reader / writer function (transmission main), L1> L2 Set. In the reader / writer function of the main transmission, it is preferable to make the resistance value R of the DC resistance component as small as possible. However, a certain inductance value L is necessary. If the inductance value L is too small, radio waves will not fly, so that desired specifications (performance and specifications such as transmission characteristics and reception characteristics) cannot be satisfied.

  In this embodiment, as in the example of FIGS. 2 and 3, the inductance value L1 is configured to be 4 turns (N1 = 4) by the number of turns of the coil, and the inductance value L2 is configured to be 2 turns (N2 = 2) by the number of turns of the coil. . Here, the inductance values are set to L1 = 1 μH and L2 = 0.5 μH, for example.

  As described above, it is convenient in terms of circuit design to set ½ × L1 = L2 in view of the specifications of each function. Considering the pattern arrangement and the like, it is preferable that the terminals A, B, and C are arranged close to each other. Therefore, the number of turns N1 and N2 is an integer, and the tap 12 in the middle at a position where the loop antenna 11 is wound by one or more turns. To set inductance values L1 and L2. That is, when the reactance value is expressed by the number of turns, it is preferable that N1> N2 ≧ 1, and in the appropriate specific example described above, 1/2 × N1 = N2 (that is, N1 = 2 × N2) is preferable. Thus, by setting the number of turns N1 and N2 of the loop antenna 11 to integers, the terminal of the second loop from one end of the loop antenna 11 to the tap 12 can be easily installed, and a smaller antenna device is configured. it can.

  In the above example, the number of turns of the loop antenna 11 is set to 4 turns. However, if the antenna has a large opening area, N1 is set to about 3 turns and N1 and N2 are set appropriately. Good.

  According to the first embodiment described above, in an RFID antenna device having a card function and a reader / writer function, the antenna element of one loop antenna is optimal for each function without increasing the antenna area. A reactance value can be realized. Therefore, it is possible to satisfy the required performance in each function while being adaptable to the downsizing of the apparatus.

(Second Embodiment)
FIG. 4 is a diagram showing a schematic configuration of a portable information terminal according to the second embodiment of the present invention. The second embodiment shows a configuration example in which the antenna device of the first embodiment is mounted on a portable information terminal such as a mobile phone.

  The portable information terminal 110 of this embodiment includes an antenna device 101, an RFID control unit 103, a memory 104, an interface (I / F) unit 105, a central control unit 111, a display unit 112, an input unit 113, an information storage unit 114, a wireless A communication unit 115 is provided.

  The antenna device 101 has the configuration of the first embodiment, and performs data transmission / reception by non-contact communication between the external reader / writer 200 and the IC tag 210. The RFID unit 15 performs processing related to transmission / reception of analog signals transmitted / received from the loop antenna 11 such as detection, modulation / demodulation, and clock extraction. The RFID unit 15 controls the switch 14 to switch the transmission line between a card function for communicating with the reader / writer 200 and a reader / writer function for communicating with the IC tag 210.

  The RFID control unit 103 comprehensively controls processing of transmission / reception data and other operations of the RFID unit 15. The RFID control unit 103 is connected to a memory 104 that stores information related to RFID. The memory 104 includes a flash memory that can be written without holding a power source, and data such as value information such as electronic money and electronic tickets exchanged with the reader / writer 200 and the IC tag 210, and these electronic money and electronic tickets. An application for realizing the RFID function is stored. Note that the memory 104 and the like may be provided in the RFID unit 15 of the antenna device 101.

  The interface unit 105 is a functional module for connecting the RFID control unit 103 to the main body of the mobile terminal device 110. Data written in the memory 104 can be transferred to the main body of the portable information terminal 110 via the interface unit 105.

  The central control unit 111 includes, for example, a microprocessor, a RAM, a ROM, and the like, and the microprocessor performs various processes related to the operation of the portable information terminal 110 using the RAM as a work area according to the program code stored in the ROM. Execute. The central control unit 111 can access the RFID unit 15 via the interface unit 105. The central control unit 111 is connected to an information storage unit 114 that stores various types of information such as applications and content data. The information storage unit 114 is configured by a writable flash memory or the like, and a fixed memory inside the terminal, a removable memory card, or the like is used.

  The display unit 112 is configured by, for example, a liquid crystal display. The display unit 112 can output and display the state of the RFID function, various processing results, content data reproduction results, and the like, and notify the user. The input unit 113 includes a push button key, a multi-directional switch, a jog dial, or a touch panel arranged on the display screen of the display unit 112, and the user inputs an operation instruction or data to the portable information terminal 110. Used to do. The wireless communication unit 115 is a functional block having a wireless communication function for performing mobile communication such as a mobile phone, and can communicate with other terminals via an external base station or the like. Each unit of the portable information terminal 110 is driven by power supply from a main power source (not shown) such as a battery.

  When the card function is executed, contactless data communication is started between the antenna device 101 and the reader / writer 200 by holding the portable information terminal 110 close to the reader / writer 200. Then, after verifying the PIN number such as PIN, the reader / writer 200 is allowed to access value information such as an electronic ticket and electronic money in the memory 104, and data is read and written. At this time, the switch 14 of the antenna device 101 is turned off, and the transmission line for the reader / writer function is disconnected.

  On the other hand, when reading or writing information of the IC tag 210 by executing the reader / writer function, the switch 14 is turned on, the reader / writer function transmission line is connected, and the RFID writer 15 transmits a reader / writer function transmission signal. Output. Thereby, a part of the loop antenna 11 is caused to function and transmit to the IC tag 210 to start non-contact data communication. At this time, the IC tag 210 is activated by the radio wave radiated from the loop antenna 11. Next, data is read from the IC tag 210 by receiving radio waves radiated from the IC tag 210 with the entire loop antenna 11 functioning. Information read from the IC tag 210 can be decoded by the RFID control unit 103 and stored in the memory 104 or displayed on the display unit 112.

  In the second embodiment described above, the antenna device shown in the first embodiment is mounted, and the function of the card function and the reader / writer function can be achieved without increasing the antenna area by the antenna element of one loop antenna. On the other hand, an optimum reactance value can be set. For this reason, it is possible to realize a portable information terminal including an RFID that can be adapted to downsizing of the apparatus and that satisfies the performance required for each of the card function and the reader / writer function.

  It should be noted that the present invention is not limited to those shown in the above-described embodiments, and those skilled in the art can also make changes and applications based on the description in the specification and well-known techniques. Yes, included in the scope of protection.

  The present invention can be adapted to downsizing of the apparatus without increasing the antenna area when setting both the RFID card function and the reader / writer function, and sets an optimum reactance value for each function. For example, it is useful as an antenna device and a portable information terminal used in an RFID system such as Felica (registered trademark).

The figure which shows schematic structure of the antenna device which concerns on the 1st Embodiment of this invention. The figure which shows the structural example of the loop antenna which concerns on this embodiment The figure which shows the relationship of the reactance value (the number of turns N or the inductance value L) of the loop antenna which concerns on this embodiment The figure which shows schematic structure of the portable information terminal which concerns on the 2nd Embodiment of this invention. The figure which shows the 1st example of the conventional antenna device used for RFID which has two functions. The figure which shows the 2nd example of the conventional antenna apparatus used for RFID with two functions.

Explanation of symbols

11 Loop antenna 12 Tap 13 Capacitor 14 Switch 15 RFID part 16 Receiving circuit (card function and reader / writer function)
17 Transmitter circuit (card function)
18 Transmitter circuit (Reader / writer function)
DESCRIPTION OF SYMBOLS 101 Antenna apparatus 103 RFID control part 104 Memory 105 Interface (I / F) part 110 Portable information terminal 111 Central control part 112 Display part 113 Input part 114 Information storage part 115 Wireless communication part 200 Reader / writer 210 IC tag

Claims (8)

An antenna device capable of supporting a card function and a reader / writer function in RFID,
A first loop having a first reactance value;
A second loop that is part of the first loop and has a second reactance value that is less than the first reactance value;
The first loop is used for transmission / reception of the card function and reception of the reader / writer function,
The second loop is an antenna device used for transmission of the reader / writer function. The antenna device according to claim 1,
The card function is a function for receiving radio waves from other reader / writers or RFID and reading data by others,
The reader / writer function is an antenna device that transmits radio waves to other RFIDs and reads data from others. The antenna device according to claim 1,
One end of the first loop is connected to a receiving circuit for the card function and the reader / writer function, and a transmitting circuit for the card function, and one end of the second loop in the middle of the first loop is An antenna device connected to the transmitter circuit of the reader / writer function. The antenna device according to claim 1,
The antenna device, wherein the second reactance value is substantially half of the first reactance value. The antenna device according to claim 1,
The first loop and the second loop are coiled loop antennas that are wound, and the second loop is an antenna device that has fewer turns than the first loop. The antenna device according to claim 5, wherein
The antenna device, wherein the number of turns of the second loop is substantially half of the number of turns of the first loop. The antenna device according to claim 1,
A signal line between one end of the second loop in the middle of the first loop and the transmission circuit for the reader / writer function is transmitted to the second loop and the reader / writer function during operation of the card function. An antenna device including a switch for separating a circuit.   A portable information terminal comprising the antenna device according to claim 1.

Images