JP5065070B2 - Antenna unit and information reader - Google Patents

Description

  The present invention is an antenna for wirelessly writing or reading information from an information recording medium that can be wirelessly written or read using electromagnetic coupling, which is used as an IC tag or an IC card, and the like. The present invention relates to an information reading apparatus that performs information writing or reading processing from an information recording medium using an antenna, and particularly relates to a technique that can expand a wireless communication area that can wirelessly communicate with the information recording medium.

2. Description of the Related Art In recent years, a system has been put into practical use in which recorded information is written or read by wireless communication by an information reading device from an information recording medium that can be written or read wirelessly, and the recorded information is used for various managements.
Recorded information is written or read by wireless communication from an information recording medium called an ID tag, IC tag, ID card, IC card or the like by an information reading device called a reader / writer device or the like. The issuing system is called an RF-ID system, a non-contact type reader / writer system, etc., and is put into practical use in a traffic card system, a physical distribution management system, an article management system, and the like.
In this specification, an information recording medium capable of wirelessly writing or reading information is referred to as an IC tag as an example, and an information reading apparatus that performs wirelessly writing or reading information from the information recording medium is referred to as an IC tag. An example is called a reader / writer device.

The non-contact type reader / writer system includes an IC tag having a loop antenna on an IC chip and a reader / writer device that performs wireless communication with the IC tag. The reader / writer device includes a loop antenna. To transmit the power for driving the IC chip in the IC tag and the query data constantly or intermittently, and obtain response data from the IC tag within the range (wireless communication area) where the power and the query data can be received. .
Here, an electromagnetic induction type reader / writer device using electromagnetic coupling using a frequency band of 13.56 MHz in the non-contact type reader / writer system will be described.

  A non-contact type IC tag (hereinafter simply referred to as an IC tag) having no built-in power supply and an electromagnetic induction type reader / writer device (hereinafter simply referred to as a reader / writer device) and wireless communication (reading of information or writing of information) Therefore, a magnetic field generated by an antenna provided in the reader / writer device (hereinafter, referred to as an RW antenna as appropriate for clarity of the reader / writer device) drives the circuit inside the IC tag. It must be strong enough to obtain the electromotive force to be generated, and satisfy the conditions of the direction and distance of linking the loop openings of the loop antenna provided in the IC tag.

Here, article management using a non-contact type reader / writer system in an environment where an IC tag is attached to each management target object and the management target object is regularly arranged in a storage place having an arbitrary size. Taking a system operation method as an example, there is a method of collectively reading a plurality of IC tags attached to respective management objects.
However, there are some problems as follows.

  For example, when a plurality of IC tags are arranged at seven locations at intervals of 0.3 m, (1) in order to read a plurality of IC tags with a single RW antenna, a loop opening of one RW antenna is provided. There is a method of increasing the size, and (2) a method of switching a plurality of RW antennas for one reader / writer device and reading a plurality of IC tags.

  In the method (1), it is possible to generate a magnetic field in a wide range. However, since the magnetic flux density is small, if the output of the RW antenna is not increased, the IC tag reading range (wireless communication area) for the RW antenna can be obtained. ) Cannot be obtained uniformly. In addition, since the Q value of the RW antenna becomes too large, a damping resistance must be inserted into the loop antenna circuit to reduce the Q value. However, this reduces the current flowing through the loop antenna, which occurs in the RW antenna. Since the magnetic field to be reduced becomes small, the IC tag reading range becomes small. Furthermore, for example, since the reading range has a total length of 1.8 m, at least the loop length of the RW antenna is 3.6 m or more, and approaches λ / 4 wavelength of 13.56 MHz, so that adjustment of antenna characteristics and stability are maintained. It becomes difficult. In addition to this, there are drawbacks that handling becomes difficult, such as RW antenna installation workability and adjustment of the RW antenna.

In the method (2), the reader / writer device switches a plurality of RW antennas and performs a reading operation in time series, and sequentially reads IC tags within the reading range of each RW antenna. In this case, since the number of switching increases as the number of connected RW antennas increases, the reading processing time increases, and it is necessary to perform one cycle of switching before reading and updating the same IC tag. There are drawbacks.
In addition, in order to sequentially switch a plurality of RW antennas and perform reading operations in this manner, for example, a control line is connected from the reader / writer device to each RW antenna, and each RW antenna is sequentially switched from the reader / writer device. To perform excitation (that is, turn on to output electromagnetic waves).

Regarding a method of reading a plurality of IC tags by switching control of a plurality of RW antennas, an invention is known in which the resonance frequency of an RW antenna is controlled to be different from the resonance frequency of another RW antenna (see Patent Document 1). .
JP 2007-68005 A

An object of the present invention is to solve the above-described conventional problems.
More specifically, in order to collectively read a plurality of IC tags with a single RW antenna, the problem of increasing the loop opening of the RW antenna and the problem of switching control of the plurality of RW antennas are solved. The purpose of this is to realize expansion of the wireless communication area.

  In the RW antenna unit according to the present invention, an antenna unit that is wirelessly connected to an information recording medium capable of wirelessly reading information using electromagnetic coupling is configured by an LC circuit, and the plurality of antenna units are cascade-connected, and the information recording When wirelessly connecting to the medium, L in the plurality of antenna units is excited simultaneously.

  An information reading apparatus according to the present invention includes an RW antenna unit in which an antenna unit wirelessly connected to an information recording medium capable of reading information wirelessly is configured by an LC circuit, and the plurality of antenna units are cascade-connected. And an excitation unit that simultaneously excites L in the plurality of antenna units of the RW antenna unit, and a read control unit that controls a process of reading information from the information recording medium.

  According to the RW antenna unit according to the present invention, when a plurality of antenna units composed of LC circuits are cascade-connected by, for example, a coaxial cable and wirelessly connected to an information recording medium, L in the plurality of antenna units is simultaneously excited. Therefore, the wireless communication area can be expanded without excessively increasing the L loop opening in each antenna unit and without complicating the structure and control related to switching control.

  Further, according to the information reading apparatus according to the present invention, it is possible to collectively read information from a plurality of information storage media existing in the extended wireless communication area using the RW antenna unit.

The present invention will be described in detail with reference to an embodiment shown in the drawings.
FIG. 1 shows an overall configuration of a reader / writer device (information reading device) according to an embodiment of the present invention.
The reader / writer apparatus of this example includes an apparatus main body 1 and an RW antenna unit 2, an RW main body antenna 1 a connected to the apparatus main body 1, and a relay antenna 2 a constituting a part of the RW antenna unit 2. Are connected to the apparatus main body 1 by connecting them wirelessly.

The RW antenna unit 2 of this example has a configuration in which seven antenna units 3 and a relay antenna 2a are cascade-connected, and these antenna units 3 are wirelessly connected to an IC tag 4 existing in a wireless communication area to record the recorded information. 1 reads. Each antenna unit 3 and the relay antenna 2a are LC circuits composed of a coil (L) made of a loop antenna and a capacitor (C), as will be described later.
In the present invention, the number of the antenna units 3 constituting the RW antenna unit is one or more, and the resonance frequency determined by the relay antenna 2a and the coaxial cable 14 both constituting the RW antenna unit 2 is a desired frequency. If so, the number is not limited. In the present invention, the reader / writer device may have a configuration in which the RW antenna unit 2 is connected to the device main body 1 by a cable 5 such as a coaxial cable, as shown in FIG. In this case, the RW main body antenna 1a and the relay antenna 2a are not necessary, but the impedance matching device 1b is necessary. The impedance matching device 1b is composed of, for example, a known transformer.

As shown in FIG. 3, the apparatus main body 1 of this example includes congestion for an excitation unit 6 that excites all antenna units 3 of the RW antenna unit 2 and a plurality of IC tags 4 to be read information by the RW antenna unit 2. Congestion control means 7 for processing, and read control means 8 for controlling information reading processing from the IC tag 4 using the excitation means 6 and the congestion control means 7 are provided.
That is, under the control of the read control unit 8, the excitation unit 6 outputs the power and the query data for driving the IC chip in the IC tag 4 from all the antenna units 3 of the RW antenna unit 2 constantly or intermittently, The congestion control means 7 performs a congestion process of response data to the question data received by the RW antenna unit 2 and reads information from all the IC tags 4 responding to the RW antenna unit 2 to the apparatus main body 1 side.

The IC tag 4 of this example is processed from a chip piece into a card or a seal, and as shown in FIG. 4, the IC chip 10 includes a loop antenna 9. Comprises a memory 11 for recording and holding information, and a response means 12 for reading the information recorded in the memory 11 in response to the question data received by the antenna 9 and transmitting it from the antenna 9. Note that the response unit 12 transmits the information (data) read from the memory 11 from the antenna 9 with a tag ID for uniquely identifying the IC tag 4 as shown in FIG.
The IC tag 4 is extremely small, for example, is attached to each of a plurality of management objects arranged in a storage location, and information such as a delivery destination of each management object is recorded in the memory 11. The recorded information is read from the management object by the reader / writer device, and delivery management is performed using the information.

6A schematically shows a part of the RW antenna unit 2 (three parts of the antenna unit 3 and the relay antenna 2a), and FIG. 6B shows a circuit diagram of the part.
Each antenna unit 3 and the relay antenna 2a have a loop antenna L as an antenna element, and an LC circuit is formed by a coil (L) and a capacitor (C) made of the loop antenna. The RW antenna unit 2 cascades the plurality of antenna units 3 and the relay antenna 2a with the cable 14, that is, the L of the LC circuit of each antenna unit 3 is connected in parallel with each other so that the L of each antenna unit 3 is connected in parallel with each other. The two connection points connecting C are connected by a cable 14, and the apparatus main body 1 inputs driving power and question data from the relay antenna 2a at one end of the cable 14 via the RW main body antenna 1a. , Output from all the antenna units 3 of the RW antenna unit 2 all at once. That is, all the antenna units 3 are excited simultaneously. The RW main body antenna 1a and the relay antenna 2a are also composed of the same LC circuit, but the constants of L and C are set appropriately.

The connection structure using the cable 14 between the antenna unit 3 and the relay antenna 2a will be described in more detail. One end and the other end of the LC circuit are connected between the antenna unit 3 and the relay antenna 2a by cables 14a and 14b, respectively. The antenna unit 3 and the relay antenna 2a are cascaded by a pair of cables 14a and 14b.
Here, in this example, a coaxial cable 20 as shown in FIG. 7 is used as the cable 14 for cascading the antenna unit 3 and the relay antenna 2a. The coaxial cable 20 has a structure in which an inner conductor 21 is covered with an inner insulator 22, a net-like outer conductor 23 is provided outside the inner insulator 22, and the outer conductor 23 is covered with an outer insulator 24.

  In this example, the inner conductor 21 and the outer conductor 23 of the coaxial cable 20 are used as the cables 14a and 14b, respectively, but these may be reversed. Alternatively, the inner conductor 21 and the outer conductor 23 of the coaxial cable 20 may be used alternately, and the RW antenna 3 may be cascade-connected with the cable 14 including the coaxial cable 20.

  In addition, each antenna unit 3 of the RW antenna unit 2 is adjusted to a predetermined resonance frequency at which a desired reading performance for the IC tag 4 is obtained. That is, for example, as shown in FIG. 1, the RW antenna unit 2 is composed of seven antenna units 3, one relay antenna 2 a, and a coaxial cable 14 (20) that cascade-connects them, and between each antenna unit 3. When the same length, for example, a 0.3 m coaxial cable 20 is connected, and the end antenna unit 3 and the relay antenna 2a are connected by a 1 m coaxial cable 20, the loop antenna of each antenna unit 3 has the same size / The number of turns and the resonance frequency are adjusted to a resonance frequency (around 13.56 MHz) that provides the desired reading performance when all the antenna units 3 are cascade-connected. The ability to read information from 4 is about the same.

  For this reason, the resonance frequency of the antenna unit 3 alone is set in advance higher than the resonance frequency of the RW antenna unit 2 when cascaded. In addition, the resonance frequency of the RW antenna unit 2 when connected in cascade varies depending on the cable length of the coaxial cable 14 between the antenna units 3. Therefore, when it is desired to switch the intervals between the antenna units 3 in a plurality of ways, it is preferable that the resonance frequency of each antenna unit 3 can be switched according to the length between the antenna units 3.

As a method for switching the resonance frequency of the antenna unit 3 alone, for example, a series circuit of C1 and a switch SW1 is connected in parallel with C of the LC circuit of the antenna unit 3, and SW1 is opened and closed (resonance frequency switching means). The resonance frequency can be switched.
Thus, by making the cable length of the coaxial cable 14 between the antenna units 3 the same length, the resonance frequency of each RW antenna unit 2 can be easily adjusted.

  Alternatively, as shown in FIG. 8, an impedance adjusting unit 30 is connected in parallel with the LC of the antenna unit 3 and the impedance of the impedance adjusting unit 30 is adjusted to adjust the resonance frequency of the RW antenna unit 2. May be. As shown in FIG. 8, the impedance adjustment unit 30 can be configured with, for example, a variable capacitor Cv. In this case, Cv may be connected in parallel with C of the antenna unit 2. Of course, it is possible to adopt a configuration in which a plurality of fixed capacitance capacitors are switched instead of the variable capacitance capacitors.

  In the above example, the lengths of the coaxial cables connecting the antenna units 3 are the same, but they may not be the same. The resonance frequency of the RW antenna unit 2 can be adjusted by switching the impedance value of the LC circuit of each antenna unit 3 or by adjusting the impedance value of the impedance adjustment unit 30 shown in FIG.

  In the above example, the relay antenna 2a is configured by an LC circuit having the same LC value as that of the antenna unit 3, that is, the antenna unit 3 can be the relay antenna 2a. In this case, in FIG. 1, the RW antenna 2 is composed of eight antenna units. The RW main body antenna 1 a can be connected not only to the antenna unit 3 at the end of the RW antenna 2 but also to any antenna unit 3.

  In the above example, the LC value of the antenna unit 3 is set to the same value. However, even if the LC value is different for each antenna unit, the RW antenna unit 2 as a whole may be set to a predetermined resonance frequency. For that purpose, the impedance adjustment unit shown in FIG. 8 may be used, or the adjustment may be made by the impedance of each antenna unit 3.

  The resonance frequency of the RW antenna unit 2 can be expressed as an antenna having a resonance frequency f by the coil L and the capacitor C, and is expressed by the following (Equation 1).

  For example, there are three antenna units 3, each of which is L1, L2, L3, C1, C2, C3, L and C of the relay antenna 2a are L4, C4, each antenna unit 3 and relay When the capacity of the coaxial cable between the antennas 2a is Cd1, Cd2, and Cd3, and L1 = L2 = L3 = L4, L and C of the RW antenna unit 2 are expressed by the following (Expression 2) and (Expression 3). The

  Therefore, the resonance frequency of the RW antenna unit 2 can be adjusted by changing any one of the values L1 to L4, C1 to C4, and Cd1 to Cd3.

  According to the reader / writer device having the above configuration, all the antenna units 3 of the RW antenna unit 2 are excited at once by the device main body 1, and the IC tag 4 existing in the wireless communication area of each antenna unit 3 is activated to transmit the question data. To receive. When response data (recording information: see FIG. 5) is transmitted from the IC tag 4, the apparatus main body 1 receives the response data by the RW antenna unit 2.

Here, since all the antenna units 3 of the RW antenna unit 2 are excited all at once, a state in which response data is simultaneously received from the plurality of IC tags 4 by the RW antenna unit 2 occurs.
In this case, the congestion control means 7 performs a known congestion control process and correctly receives response data from each IC tag 4.
For example, response data is returned from each of the plurality of IC tags 4 at each timing in response to the inquiry data transmitted from all the antenna units 3 of the RW antenna unit 2 all at once. The congestion control means 7 of the apparatus main body 1 transmits a reception completion notification to the IC tag 4 that has returned the response data that has been received correctly, in a timely manner and without a response data return collision. On the other hand, a re-reply request (question data) including an instruction to reply at another timing is transmitted to the IC tag 4 which has replied the response data which has not been received correctly due to the collision of the reply of reply data at a poor timing. To do. The IC tag 4 that has correctly transmitted the response data to the apparatus main body 1 does not respond to this request (question data). Such transmission of question data is repeated until there is no response from the IC tag 4.

  Therefore, according to the reader / writer device described above, since the RW antenna unit that excites all the antenna units by cascading a plurality of antenna units is used, without making the loop opening of each antenna unit excessively, and The wireless communication area can be expanded without complicating the structure and control related to switching control. Furthermore, by using the RW antenna unit, information can be collectively read from a plurality of information storage media existing in the extended wireless communication area without congestion.

1 is a configuration diagram of a reader / writer device according to an embodiment of the present invention. FIG. It is a block diagram of the modification of the reader / writer apparatus which concerns on one Example of this invention. 1 is a configuration diagram of a reader / writer device main body according to an embodiment of the present invention. FIG. It is a block diagram of the IC tag which concerns on one Example of this invention. It is a figure explaining the response data based on one Example of this invention. It is a figure explaining the structure of the RW antenna part which concerns on one Example of this invention. It is a figure explaining the structure of the coaxial cable which concerns on one Example of this invention. It is a block diagram of the modification of the reader / writer apparatus which concerns on one Example of this invention.

Explanation of symbols

1: Reader / writer main unit; 2: RW antenna unit;
3: Antenna unit, 4: IC tag,
6: excitation means, 7: congestion control means, 8: read control means,
9: IC tag loop antenna 14: Cable
20: Coaxial cable, 30: Impedance adjustment unit,
L: Loop antenna (coil) of the antenna unit,
C: antenna unit capacitor,

Claims (1)

An RW antenna unit in which an antenna unit wirelessly connected to an information recording medium capable of reading information wirelessly is configured with an LC circuit, and a plurality of antenna units are cascade-connected with a cable of the same length ;
Excitation means for simultaneously exciting each antenna unit of the RW antenna unit;
Read control means for controlling information read processing from the information recording medium;
A congestion control means for performing a congestion control process for correctly receiving response data from a plurality of the information recording media;
An information reading apparatus comprising:

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