JP2002151947A - Antenna structure for rf id tag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna structure for an RF ID(Radio Frequency Identification) tag, which can stably provide its service even to the RF ID tags located over a wide range/at a remote distance and is provided with a slave station antenna with high reception/transmission sensitivity. SOLUTION: The transmission/reception antenna is configured by arranging antenna elements in a prescribed direction to form an antenna module, each of the antenna elements consists of a radiator and a reflector or consists of a wave guide, the radiator and the reflector, a semiconductor circuit is connected to the reflector, and parasitic devices are adopted for the wave director and the reflector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in an antenna structure of an RFID tag.

[0002]

2. Description of the Related Art Conventionally, as a technique for recognizing various kinds of information using an optical reader, a bar code system is most widely used. A system using a barcode can perform various management of the product by expressing the number of a product or part, a product name, a price, and other information by a one-dimensional or two-dimensional barcode, and can perform various management of the product. It is also used in POS (point-of-sale information management) systems such as inventory management, process management, entry / exit management, and stores. Barcodes have the advantage that they can be used easily, but they have the disadvantage that the amount of information that can be stored is relatively small, and that some information cannot be rewritten or added. On the other hand, as a non-contact type individual identification system using radio waves, an RFID (Radio Frequency Iden) using a transponder (transceiver) generally called a tag (RFID tag) is used.
tification) system, for example, tag (non-contact ID)
Tag) is embedded in tableware and trays to perform automatic payment processing in the cafeteria, and a system applied to ski lift lift tickets and the like. An RFID system generally includes one tag (transponder), its reader or reader / writer, and one computer or information processing system. FIG.
FIG. 1A shows an example of a tag (hereinafter, referred to as an RFID tag) applied to the above-described RFID system. FIG. 1A is a cross-sectional plan view showing the structure of the RFID tag, and FIG. It is sectional drawing. In the RFID tag 1 in this example, a circular concave portion is provided in the center of a disk-shaped resin holder 1c, and an electronic element is built in the bottom of the concave portion.
A C chip 1b and an antenna coil 1a are provided, and the upper part thereof is covered with a resin mold 1d so as to be flat. Conventionally, such a planar RFID tag 1
Is attached to or embedded in an individual to be identified.

[0003]

SUMMARY OF THE INVENTION RFID as described above
The system has an advantage that it can store a larger amount of information than a barcode and can be configured to be rewritable. In addition, there is an advantage that it can read through substances such as dust, paint, mud, plastic, and wood, has high reading accuracy, and is difficult to forge. On the other hand, barcodes are cheaper than RFID tags,
There is an advantage that it can be easily used. However, the bar code has a drawback that it cannot be read unless the surface of the reading unit on the reader side matches the surface of the bar code, and the RFID tag also has a base station reader / reader / writer in the direction of its antenna. There is a drawback that data cannot be transmitted and received unless they are arranged. Therefore, there is a problem that both cannot be used for an object whose identification target surface is not constant. Furthermore,
If the power radiated from the transmitting antenna of the base station is fixed, the slave station antenna with the highest receiving sensitivity is
It has been desired from RFID systems because the service can be provided stably even for tags over a wider range / distance. SUMMARY OF THE INVENTION The present invention has been made in view of the circumstances described above, and an object of the present invention is to provide a slave station having a high reception / transmission sensitivity capable of stably providing a service even to tags in a wider range and a longer distance. An object of the present invention is to provide an antenna structure of an RFID tag having an antenna. Another object is to provide an RFID antenna structure that can be easily used and reused.

[0004]

SUMMARY OF THE INVENTION The present invention relates to an antenna structure of an RFID tag, and the object of the present invention is to provide a plurality of antenna elements arranged in a predetermined direction along a predetermined direction. Form an antenna module, these antenna elements consisting of radiators, reflectors, or
A waveguide, a radiator, a reflector, and a semiconductor circuit connected to the radiator, the director and the reflector,
This is achieved by disposing the antenna without power supply and forming a transmitting / receiving antenna.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiments described below,
A plurality of antenna elements are arranged and arranged along a predetermined direction, and these antenna elements are electromagnetically coupled to form one antenna group, which is then combined with one semiconductor circuit (IC chip). Or a silicon chip), or a structure including an RFID tag including two or three antenna groups having different directivities and one to three semiconductor circuits is referred to as an “RFID unit”. Call and explain. Also, a group of antenna elements arranged in a predetermined direction of the RFID unit will be described as an “antenna module”. RF according to the present invention
The ID unit 1 performs both power reception and data transmission / reception.
The antenna module includes an antenna module including the antenna groups 1 to 3, and the semiconductor circuits 1 to 3 having a memory in which information can be rewritten. In addition, by forming the above-mentioned RFID unit into an antenna structure disposed on the surface portion, the inner wall portion, or the hollow portion of the ball-shaped spherical structure, it is possible to receive radio waves from almost all directions viewed from the center of the sphere. , Radio waves can be emitted in almost all directions. Also,
As a package of the RFID unit, for example, a structure formed in a ball shape is used, and the above-described antenna modules 1 to 3 are arranged on a surface portion, an inner wall portion, a hollow portion, or the like. And simple and inexpensive RFI
As the configuration of the D unit, one to three seal-type RFID tags each including one antenna group and one IC chip are used, and these RFID tags are fixed to a ball-shaped structure, so that the D-units are substantially omnidirectional. RFID that can send and receive radio waves
The unit has been realized. Also, on the base station reader side of the RFID unit having the RFID tags 1 to 3,
For example, the RFID that first received a response to a query
By transmitting a transmission stop command to the tag and accepting response data from the other RFID tag, it can be easily applied to a general RFID system.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 shows an antenna structure including one antenna module and one semiconductor circuit as an example of the antenna structure of the RFID unit according to the present invention. That is, in FIG.
The FID 10 includes an antenna element 11a, 11b, 11c that performs both power reception and data reception / transmission, and a semiconductor circuit 12
Are attached to the housing 13. In this example, a plurality of antenna elements are arranged in a predetermined direction and are arranged, and these antenna elements
a, the radiator 11b, and the reflector 11c are respectively configured;
The radiator 11b is connected to the semiconductor circuit 12 and can supply power. The director 11a and the reflector 11c are arranged without power supply, and are electromagnetically coupled to each other to form one transmission / reception antenna. Is formed. Further, the length of each antenna element is determined by the frequency of a radio frequency signal to be transmitted and received, and preferably has a length of an integral multiple of approximately λ (wavelength) / 2. The number of the above-mentioned antenna elements is preferably 1 to 10 for the director 11a, one for the radiator 11b, and one for the reflector 11c. Next, FIG. 3 shown corresponding to FIG.
Shows an antenna structure using two antenna modules and two RFID tags each including two semiconductor circuits as another example of the antenna structure of the RFID unit according to the present invention, and the same numbers are assigned to the respective antenna modules. The device performs the same function, and in the example of FIG. 3, the transmitting and receiving antenna modules 10a and 10b are respectively disposed along the first and second directions forming different angles from each other, and And the angle formed by the second antenna is 9
Preferably, the angle is set to 0 degrees, and in such a state, the first and second transmitting / receiving antennas / RFIDs are arranged on the surface portion, the inner wall portion, or the hollow portion of the seat 20 or the ball-shaped spherical structure. It has become.

Further, FIG. 4 shown corresponding to FIGS. 2 and 3
Are three antenna modules and three antennas as another example of the antenna structure of the RFID unit in the present invention.
4 shows an antenna structure using three RFID tags each composed of one semiconductor circuit. Devices with the same numbers perform the same functions, and in the example of FIG.
The transmitting and receiving antenna modules 10a to 10c are respectively shifted along first to third directions forming different angles from each other,
And the angles formed by the first to third antenna modules are set to 90 degrees, respectively, so-called X, Y,
It is preferable to dispose in the Z-axis direction, and in such a state, the first to third transmitting / receiving antennas / RFIDs are arranged on the surface portion, the inner wall portion, or the hollow portion of the ball-shaped spherical structure 30. Has become. By the way, as an ID semiconductor circuit (chip), a circuit using various radio waves or a circuit using a high-frequency radio wave (microwave band) is applied. Which chip to use is determined by the field to which it is applied.For example, in the case of comprehensive management from the product manufacturing stage to distribution and sales, use a transponder element that can transmit at a long distance. Is preferred. Note that a configuration in which a plurality of antenna modules as described above are connected to one semiconductor circuit without providing one semiconductor circuit corresponding to one antenna module may be adopted. However, in order to make the configuration inexpensive, it is preferable that each antenna module is connected to each semiconductor circuit. In addition, as shown in FIG. 4, when an RFID unit is configured using three RFIDs, for example, the ball-shaped structure 30 is formed as a package so as to intersect each other in the orthogonal direction on the spherical surface thereof. Three RFID10,
By arranging and fixing along the X, Y, and Z axes, the antenna has the above-described antenna structure, and can receive radio waves from almost all directions viewed from the center, and transmit radio waves to almost all directions. An RFID unit 30 capable of emitting light can be realized. In addition, three RFs as described above
If the ball-shaped structures 30 arranged so that the IDs are orthogonal to each other are provided in, for example, a rectangular parallelepiped package, an RFID unit 30 having an arbitrary shape can be realized. As the housing / packaging member of the RFID 10, any member having a high transmittance of radio waves in the frequency band used for transmitting and receiving signals may be used.

Next, the configuration of the base station information processing apparatus that performs processing such as reading / writing of the RFID unit will be described. As the read / write device of the RFID unit, a general read / write device can be used.
It is composed of an SK (Frequency Shift Keying) demodulator, an excitation drive, a control CPU, and the like. In the present invention, R
The FID unit includes three RFIDs (tags) having transmission / reception area portions in different directions from each other.
Since the same data is stored in the storage unit of the ID tag, three responses are generated to the inquiry (interrogation radio wave). Therefore, in the data reading process, only one response data needs to be processed.

A control CPU (or a control CPU) in a read / write device on the base station side of the RFID unit according to the present invention will be described below.
An operation example of the host computer will be described with reference to the flowchart of FIG. The control CPU in the read / write device of the RFID unit transmits an inquiry signal for reading on a carrier wave (step S1). RFID
On the unit side, necessary power is generated by the carrier wave, and the power is used for writing / reading and transmission of data.
The D information is retransmitted as a reflected wave modulation signal via the antenna module. In this example, the RFID unit includes three RFIDs (tags), and response signals having the same contents are transmitted by independent operations. The control CPU of the read / write device determines whether or not a response to the inquiry has been received (step S2), and when the response is received, the RFID (for example, the RFID which first responded).
A transmission stop command is sent to the user (steps S3 and S4).
Then, a response from another RFID is received (step S5), and information processing such as identification processing is performed using the response data (step S6). Thus, RFI
In the read / write device on the master station side of the D unit, at the time of receiving a response to the inquiry during the reading process, the first RF
It is sufficient to provide a step (or a circuit) for transmitting a transmission stop command to the ID (the RFID that has received the response first in this example), and it is not necessary to change the identification processing on the device side or the interface with the RFID.

Next, an example of a system to which the RFID unit according to the present invention is applied will be described. FIG. 6 shows an example of a system in which a "basket" (or pallet) 62 loaded with products is transported by a transport means such as a conveyor 63, and the products are sorted and shipped according to delivery destinations and product types. Although a general system uses a barcode, the system cannot be used when a container such as a "cage" or the like in which the surface of the barcode is not constant is used. For example, in agricultural cooperatives, generally, articles such as cucumber, apples, and oranges are put in a "basket" 62 and transported on a conveyor 63, and are shipped by hand. In the past, information such as information that has been deleted has been managed manually and has not been mechanized. Therefore, if an RFID tag reading device (or reading / writing device) 64 is provided by using the RFID unit of the present invention, a system for reading and managing data such as which agricultural cooperative and who has shipped it can be constructed at low cost. can do.
For example, a ball-shaped RFID unit in which a distribution channel is written in advance (a ball-shaped RFID having a size of a golf ball)
Unit) 30 at the beginning of the "basket" (or pallet)
By simply throwing the data into the storage 62, a system can be realized in which the reading device 64 can read data such as who shipped the product by treating the agricultural cooperative. Further, if the RFID unit is taken out from the "car" 62, it can be reused. With such a usage form, introduction of the RFID system is very simple and operation is easy. In the above-described embodiment, the RFID unit is described as an example of a passive type that obtains operating power from energy emitted by a reader, but may be an active type with a built-in battery. In addition, R without mounting part
Although the FID unit has been described as an example, a unit configuration having a mounting portion may be used.

[0011]

As described above, according to the present invention, an RFID provided with a local station antenna having high reception / transmission sensitivity capable of stably providing a service even for tags in a wider range and a longer distance. An antenna structure of the tag and an RFID unit can be provided. Further, an RFID unit that can be easily used and reused can be provided. In addition, since the three antenna modules have an antenna structure in which the surfaces of the three antenna modules are arranged at an angle of 90 degrees to each other in a spherical container, transmission and reception of radio waves in almost all directions becomes possible. An RFID unit that can be used in the field can be provided. In addition, by adopting a unit form in which the RFID is fixed to the ball-shaped structure, an inexpensive, easily usable and reusable RFID unit can be provided.
Further, the base station reading device side of the RFID unit only needs to provide a step (or circuit) of transmitting a transmission stop command to the initial RFID tag that has received the response and receiving the response of the last RFID tag. There is no need to change the identification processing on the device side or the interface with the RFID, and the RFID unit can be easily applied.

[Brief description of the drawings]

1A and 1B are a plan view and a side sectional view illustrating a structure of a general RFID tag.

FIG. 2 is a diagram showing an example of the structure of an RFID antenna module according to the present invention.

FIG. 3 is a diagram showing an example of another structure of the RFID antenna module according to the present invention.

FIG. 4 is a diagram showing still another example of the structure of the RFID antenna module according to the present invention.

FIG. 5 is a flowchart for explaining an operation example on the reading device side of the RFID unit according to the present invention.

FIG. 6 is a schematic diagram showing an example of a system to which the RFID unit according to the present invention is applied.

[Explanation of symbols]

 10, 10a, 10b, 10c RFID 11a Director 11b Radiator 11c Reflector 12 Semiconductor circuit 13 Container 20 Sheet-like structure 30 Ball-like structure

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01Q 23/00 G06K 19/00 K F-term (Reference) 5B035 AA07 BA05 BB09 CA01 CA23 5J020 AA03 BA02 BC09 DA02 5J021 AA09 AB03 CA06 FA32 GA08 HA05 HA10 5J070 AE20 AF01 AF02 AK01 AK13 BC06 BC23 BC25 BC33

Claims (8)

[Claims] 1. An antenna structure of an RFID tag,
Along a predetermined direction, a plurality of antenna elements are arranged and arranged to form an antenna module, and these antenna elements are composed of a radiator and a reflector, or a director, a radiator, and a reflector. An antenna for an RFID tag, wherein a semiconductor circuit is connected to the radiator, and the director and the reflector are arranged without power supply to form a transmitting / receiving antenna. Construction. 2. The RFI according to claim 1, wherein each of the plurality of antenna elements has an integral multiple of λ / 2.
Antenna structure of D tag. 3. The R antenna according to claim 1, wherein the transmitting and receiving antenna modules are arranged along first and second directions forming different angles from each other.
Antenna structure of FID tag. 4. The RFID according to claim 3, wherein the angle formed by the first and second antenna modules is 90 degrees.
Tag antenna structure. 5. The RFID antenna according to claim 3, wherein the first and second transmitting / receiving antenna modules are arranged on a surface portion, an inner wall portion, or a hollow portion of the ball-shaped spherical structure. Construction. 6. The transmission / reception antenna module according to claim 1, wherein said transmission / reception antenna modules are respectively arranged along first, second, and third directions forming different angles from each other. The antenna structure of the RFID tag described in 1. 7. The antenna structure according to claim 6, wherein the first, second, and third antenna modules form an angle of 90 degrees with each other. 8. The method according to claim 6, wherein the first, second, and third transmitting / receiving antenna modules are arranged on a surface portion, an inner wall portion, or a hollow portion of the ball-shaped spherical structure. The antenna structure of the described RFID.