JP5027178B2 - leader - Google Patents

Description

  The present invention relates to a reader that can read information of an information code and an RFID tag.

  This type of reader can optically read information codes such as bar codes and two-dimensional codes, and can read information stored in RFID tags through radio signals. When a reader reads information stored in an RFID tag, generally, the information stored in the RFID tag is read by transmitting / receiving information to / from the RFID tag using radio waves having a frequency of a microwave or UHF band.

  Considering the polarization characteristics of electromagnetic waves, when a linearly polarized antenna is used for the reader antenna and the RFID tag antenna, the communication (reading) distance depends on the position of the reader relative to the RFID tag (angle between antennas). There is a problem that changes greatly.

  Therefore, conventionally, the above problem is solved by adopting a circularly polarized antenna as the reader-side antenna. On the other hand, when the reader optically reads the information code, in order to read the information of the information code accurately, it is necessary to read the reading port toward the information code.

  This kind of technical idea is disclosed in Patent Documents 1 to 3. According to the technical idea described in Patent Document 1, reading is performed in the same direction by mounting an antenna close to an optical unit for reading a barcode. However, as indicated by the technical idea described in Patent Document 1, if the antenna is enlarged in order to increase the gain, the barcode reading field of view is obstructed, and there are many restrictions on the arrangement position.

  Further, according to the technical idea of the patch antenna disclosed in Patent Document 2, the directivity is well maintained in the installation direction of the road antenna by combining a plurality of patch antennas and changing the directivity. Even if this technical idea is applied to the antenna on the reader side, it is not preferable because the mounting volume increases because the radiation surface of the patch antenna is changed by the inclination.

In addition, it is suitable for the user's use that the reading direction of the information code and the reading direction of the RFID tag by the power feeding element are substantially the same, and this kind of technology is desired.
On the other hand, FIGS. 14 to 17 show a conventionally known antenna structure. FIG. 14A and FIG. 14B show a general dipole antenna and its directivity. In this dipole antenna 100, the antenna element 102 extends to both sides of the feeding point 101, and the directivity becomes stronger in the direction orthogonal to the extending direction of the antenna element 102.

FIGS. 15 (a), 15 (b), 16 (a), and 16 (b) show a two-element Yagi antenna and its directivity, respectively.
As shown in FIG. 15A or FIG. 16A, the parasitic element 103 is provided so as to be separated in the direction orthogonal to the extending direction of the antenna element 102 of the dipole antenna 100. As shown in FIGS. 15B and 16B, the parasitic element 103 functions as a director or a reflector according to the distance from the antenna element 102.

  FIGS. 17A and 17B show the antenna disclosed in Patent Document 3 and its directivity. In the technical idea described in Patent Document 3, unidirectionality is realized by feeding power to two dipole antennas and causing a short antenna element to function as a director. For example, in the structure shown in FIG. 17A, since the power feeding is branched, the power feeding structure becomes complicated, and the loss increases as compared with the one-point power feeding.

JP 2004-157744 A JP 2007-288398 A JP 2007-020093 A

  The present invention has been made in view of the above circumstances. The reading direction of the RFID tag is made compact while keeping the reading direction of the information code and the reading direction of the RFID tag substantially the same direction and suitable for user use. It is an object of the present invention to provide a reader capable of increasing the gain.

  According to the first aspect of the present invention, the information code can be optically read via the reading port by the optical information reading mechanism, and the radio wave communication mechanism reads the information stored in the RFID tag via the radio signal. be able to. A feeding element using a patch antenna mainly transmits and receives radio signals and communicates with an RFID tag. Since the parasitic element is arranged around the reading port of the optical information reading mechanism, when the user communicates with the RFID tag with the reading port of the optical information reading mechanism facing the RFID tag, the parasitic element is guided. The antenna gain can be increased by functioning as a waver. In addition, since the parasitic element is disposed so as to surround the reading port with a U-shaped linear member, it can be disposed in the vicinity of the reading port without obstructing the reading field by the optical information reading mechanism. . As a result, the reading direction of the information code and the reading direction of the RFID tag can be made substantially the same direction to be in a state suitable for user use, and the gain in the reading direction of the RFID tag can be increased while downsizing.

According to the first aspect of the present invention, the information code can be optically read via the reading port by the optical information reading mechanism, and the radio wave communication mechanism reads the information stored in the RFID tag via the radio signal. be able to. A feeding element using a patch antenna arranged at a different location from the optical information reading mechanism mainly transmits and receives radio signals and communicates with the RFID tag. Since the parasitic element is disposed on the side of the reading port side of the optical information reading mechanism, when the user communicates with the RFID tag with the reading port of the optical information reading mechanism facing the RFID tag, the parasitic element Can function as a director to increase the antenna gain. In addition, since the parasitic element is disposed so as to surround the reading port with a U-shaped linear member, it can be disposed in the vicinity of the reading port without obstructing the reading field by the optical information reading mechanism. . As a result, the reading direction of the information code and the reading direction of the RFID tag can be made substantially the same direction to be in a state suitable for user use, and the gain in the reading direction of the RFID tag can be increased while downsizing.

  As in the invention according to claim 4, the parasitic element may be provided with a matching element, and, as in the invention according to claim 5, the line segment part in which the parasitic element extends linearly and the line segment. A bent portion that is bent in a zigzag manner at a bent portion at both ends of the line segment when the bent portion is formed with a bent portion that is bent at both ends of the portion. A parasitic element may be configured. In such a case, the antenna matching according to the transmission / reception frequency can be easily performed, and even if there is a restriction on the shape of the parasitic element, the restriction condition can be flexibly dealt with.

  As in the invention according to claim 6, when the parasitic element is formed in a U-shape including a line segment part and bent parts located at both ends of the line segment part, the line segment part Is disposed on the ground plane side of the patch antenna, the characteristics of the antenna as a waveguide can be kept good. As in the invention according to claim 7, the bent portion may be disposed close to the ground plane side of the patch antenna, and the line segment may be spaced apart from the ground plane of the patch antenna. In addition, as in the invention according to claim 8, when the feeding element and the parasitic element are incorporated, the size can be further reduced.

FIG. 1A is a longitudinal sectional side view schematically showing a structure inside a reader, and FIG. 2B is a schematic view showing a configuration of parasitic elements in the vicinity of a reading opening. Figure showing Block diagram schematically showing the electrical configuration of the reader (A) and (b) are antenna structures and their directional characteristics (part 1). (A) and (b) are antenna structures and their directional characteristics (part 2). (A) and (b) are antenna structures and their directional characteristics (Part 3). (A) and (b) are antenna structures and their directional characteristics (part 4). (A) and (b) are diagrams showing the antenna structure and its current distribution (part 1). (A) and (b) are diagrams showing the antenna structure and its current distribution (part 2). (A) (b) is a diagram showing the antenna structure and its current distribution (No. 3) (A) (b) is a diagram showing the antenna structure and its current distribution (No. 4) (A) (b) is a figure which shows the antenna gain according to the arrangement position of a parasitic element (the 1) (A) (b) is a figure which shows the antenna gain according to the arrangement position of a parasitic element (the 2) The figure which shows an example of the antenna structure about the 2nd Embodiment of this invention (A) and (b) are antenna structures and their directional characteristics diagrams showing a conventional example (part 1). (A) and (b) are antenna structure diagrams and their directivity characteristics diagrams showing a conventional example (part 2). (A) and (b) are antenna structure diagrams and their directivity characteristics diagrams showing a conventional example (part 3). (A) and (b) are antenna structure diagrams and their directivity characteristics diagrams showing a conventional example (part 4).

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1A schematically shows the appearance and internal structure of a barcode / RFID tag reader.
The barcode / RFID tag reader 1 (hereinafter referred to as a reader) is configured to be capable of optically reading the barcode B and, for example, an electromagnetic wave (for example, 950 MHz) with the RFID tag 2 attached to an article such as a product. UHF band radio waves) are used to supply power and read data. When communication is performed using radio waves in the UHF band, communication over a long distance is possible as compared with, for example, the HF band and the microwave band. In this embodiment, a communication distance of about several tens of centimeters is assumed. In the present embodiment, an embodiment applied to the reader 1 that omits the writer function is shown.

  The reader 1 is of a handy type that can be carried by a user. The RFID tag 2 is configured, for example, in the form of a plastic tag, and has an antenna (not shown) on the tag side for performing communication with the reader 1 inside, as well as data holding and response signals. And an RFID chip (not shown) that responds to the reader 1.

  The RFID tag 2 includes a rectifying and smoothing circuit for obtaining an operating power supply from a power supply signal of the reader 1, a CPU for controlling communication, a modulation / demodulating circuit for modulating and demodulating transmission / reception signals, an operation program, data, and the like. The memory to be stored is configured as a single chip. In the memory of the RFID tag 2, data relating to a product to be attached is stored.

  In the case (housing) 4, the reader 1 has a radio wave communication mechanism 5 that performs radio wave communication with the RFID tag 2, an optical information reading mechanism 6 that optically reads the barcode B, a control circuit 7, a display The unit 8, the operation unit 9, the battery pack 10 and the like are incorporated.

  The case 4 has a grip portion on the base end side (the right side in FIG. 1A), and the tip end side (the left side in FIG. 1A) gradually increases in width and tilts downward. In this way, the front end is a reading port 4a. As shown in FIG. 1B, the structure in the vicinity of the reading port 4a, the reading port 4a has a horizontally long rectangular shape.

  An operation unit 9 is provided on the upper surface of the case 4 on the base end side. The operation unit 9 includes a plurality of key switches 9a. A display unit 8 made of an LCD is provided on the top surface of the case 4 on the front end side. The case 4 is also provided with a trigger key (not shown) for reading instructions. The control circuit 7, the display unit 8, and the key switch 9 a are mounted on a printed wiring board 11 provided in the case 4. The battery pack 10 is built in the lower side of the base end side of the case 4.

  The optical information reading mechanism 6 includes an image pickup device 12 such as a CCD area sensor and is composed of a camera unit 13 and the like disposed in the vicinity of the inside of the reading port 4a. An image pickup signal of the image pickup device 12 is transmitted by a cable 14 and a printed wiring board. 11 is provided to the control circuit 7. The camera unit 13 is configured by unitizing an illumination light source 16 including an imaging element 12, an imaging lens 15, and a plurality of LEDs.

  Therefore, when the user performs a reading operation with the reading port 4a of the case 4 facing the reading target, the illumination light from the illumination light source is irradiated onto the reading target, and the reflected light enters through the imaging lens 15. , Enters the image sensor 12. The control circuit 7 performs a decoding process of the barcode B from the captured image data incident on the image sensor 12.

FIG. 2 schematically shows an electrical configuration block of the radio wave communication mechanism.
The radio wave communication mechanism 5 includes a reader-side antenna 17, a transmission circuit 18 connected to the reader-side antenna 17, and a reception circuit 19. The antenna 17 includes a feeding element 17a and a parasitic element 17b disposed around the feeding element 17a.

  As shown in FIG. 1 (a), the antenna 17 a of the reader 1 is disposed substantially at the center on the lower surface side of the case 4. The power feeding element 17 a is disposed between the battery pack 10 and the camera unit 13. The feed element 17a has an antenna substrate (no symbol) formed of a ceramic dielectric material as a base material, and includes an antenna surface 17aa (antenna element) of a patch antenna on the lower surface side, and an upper surface side of the antenna substrate. Are provided with a ground surface 17ab of the patch antenna. Both the antenna surface 17aa and the ground surface 17ab are made of a conductive material such as copper foil, and are formed in, for example, a rectangular shape (square shape) in the depth direction and the left-right direction in FIG. The antenna surface 17aa is narrower than the ground surface 17ab.

  A modulation signal is supplied from the control circuit 7 to the antenna surface 17aa of the feed element 17a through a microstrip line, a coaxial line, or the like. The antenna surface 17aa is configured as a conductor surface along a horizontal plane (left and right direction and depth direction in FIG. 1A), and can transmit and receive circularly polarized radio waves. The main propagation direction with high directivity of the radio signal may be the front lower direction D2 slightly forward compared to the lower direction (vertical direction) D1. This is because the reading port 4a is inclined downward.

  When reading stored information from the RFID tag 2, the user may consider reading through the reading port 4 a in the same direction as when reading the barcode B, for example. Therefore, if the user can take a system for reading the information stored in the RFID tag 2 in the same reading state as the state in which the user reads the barcode B optically, the user will not feel uncomfortable and the system will be desirable. . Therefore, the main propagation direction D2 of the radio wave signal is preferably set so as to be inclined substantially coincident with the inclination of the barcode B reading direction D3.

  Thus, in order to set the main propagation direction D2 of the radio signal so as to substantially coincide with the reading direction D3 of the barcode B, in this embodiment, the parasitic element 17b is provided around the reading port 4a. Yes.

  As shown in FIG. 1B, the case tip 4c is provided so as to cover the periphery of the reading port 4a. The parasitic element 17b is made of, for example, a metal linear member, and is disposed inside the case tip 4c in the vicinity of the reading port 4a so as to be formed in a U shape (reverse C shape). . Accordingly, the parasitic element 17b is disposed in the vicinity of the reading port 4a (for example, a part of the periphery of the reading port 4a) so as to surround the reading port 4a. Thereby, it is comprised so that the image formation by the camera unit 13 through the reading port 4a and the light irradiation by the illumination light source 16 may not be inhibited. The parasitic element 17b includes a line segment 17ba that extends linearly and a bent portion 17bb that is bent at both ends of the line segment 17ba.

FIGS. 3A to 6A are plan views showing the arrangement relationship between the feeding element and the parasitic element as viewed from the lower surface side, and FIGS. 3B to 6B show the feeding element. 4 schematically shows a cross-section and directivity when the arrangement relationship of the parasitic elements is viewed from the side.
When the feed element 17a is provided as a single unit as shown in FIG. 3A, the directivity is strong toward the lower side of the patch antenna mounting side of the feed element 17a as shown in FIG. 3B. The directivity is weak at the upper side opposite to the patch antenna mounting side. In FIGS. 4B to 6B, the directivity of the patch antenna alone is indicated by a dotted line as a comparative example.

  As shown in FIG. 4A, when the linear parasitic element 17c is arranged in the vertical direction on the left side of the feeding element 17a, the front downward direction D2 as shown in FIG. 4B. Is relatively weak compared to the case of the power feeding element 17a alone.

  As shown in FIG. 5A, when a U-shaped (reverse C-shaped) parasitic element 17b is arranged in the vertical direction on the left side of the feeding element 17a, As shown, the directivity in the front lower direction D2 is relatively stronger than in the case of the power feeding element 17a alone.

  As shown in FIG. 6A, when the line segment 17ba of the parasitic element 17b is arranged so as to overlap the antenna surface 17aa of the feeder element 17a, as shown in FIG. In addition, the directivity in the front lower direction D2 is relatively weak as compared with the case of the power feeding element 17a alone. Therefore, the U-shaped parasitic element 17b is arranged so as not to overlap the feeder element 17a in a planar manner, thereby making it possible to improve the directivity characteristics in the front lower direction D2.

  7 (a) to 10 (a) and FIGS. 7 (b) to 10 (b) correspond to the plan view showing the arrangement relationship between the feeding element and the parasitic element when viewed from the lower surface side and the current distribution. It is attached. 7 to 10 show current distribution characteristics corresponding to each of FIGS. 3 to 6.

  As shown in FIGS. 7 to 10, an electric current flows upward from the lower end side to the upper end side on the antenna surface 17aa of the feeding element 17 a, and near the center from the lower end side to the upper end side, respectively. There is a belly of current distribution. As shown in FIG. 7A, when the parasitic element 17b is not arranged and the feeder element 17a is arranged alone, as shown in FIG. 7B, the upper end side of the antenna surface 17a is arranged. Current inflection point 17az is located at the center of the portion and the lower end side.

  As shown in FIG. 8A, when the linear parasitic element 17c is arranged in the vertical direction on the left side of the feeding element 17a, as shown in FIG. When the C-shaped passive element 17b is arranged, the position of the current inflection point 17az is not substantially changed, but as shown in FIG. 10A, the parasitic element 17b is flat on the power supply element 17a. When the antennas are arranged so as to overlap each other, it has been found that the resonance frequency of the antenna system shifts and the position of the current inflection point 17az moves in the direction in which the parasitic element 17b is arranged. Therefore, when attention is paid to the resonance frequency of the antenna structure, it is understood that the antenna gain is reduced when the parasitic element 17b is disposed too close to the feeder element 17a.

FIG. 11 schematically shows the positional relationship in the vertical direction (up and down direction) between the feeding element 17a and the U-shaped parasitic element 17b and its antenna gain characteristic.
As shown in FIG. 11, when the parasitic element 17b is disposed within the distance d1 = λ / 60 to λ / 10 in the vertical direction from the ground plane of the feeding element 17a, the gain is 4 [dBi]. It can be seen that the gain decreases in other ranges. Therefore, when the parasitic element 17c is arranged close to the feeder element 17a, the distance d1 from the ground plane of the feeder element 17a is preferably in the range of λ / 60 to λ / 10.

FIG. 12 schematically shows the positional relationship in the horizontal direction between the feeding element 17a and the U-shaped parasitic element 17b and the gain characteristics thereof.
As shown in FIG. 12, when the parasitic element 17b is disposed within the horizontal distance d2 = 0 [mm] to λ / 15 from the left side end of the feeder element 17a, the gain is 4 [ dBi], and the gain decreases in other ranges. Therefore, when the parasitic element 17b is disposed close to the feeder element 17a, the distance d2 from the end of the left side of the feeder element 17a is preferably in the range of 0 [mm] to λ / 15. With such an arrangement, the antenna can be further increased in gain.

As described above, according to the present embodiment, since the parasitic element 17b is disposed around the reading port 4a, the user installs the reading port 4a of the optical information reading mechanism 6 toward the RFID tag 2. When communicating with the RFID tag 2, the parasitic element 17b functions as a waveguide, so that the antenna gain can be increased. In addition, since the parasitic element 17b is positioned around the reading port 4a so as to surround the reading port 4a, no parasitic power is supplied to the vicinity of the reading port 4a without obstructing the reading field by the optical information reading mechanism 6. An element 17b can be provided. As a result, the reading direction D3 of the barcode B and the reading direction D2 of the RFID tag 2 can be made substantially the same direction to be in a state suitable for user use, and a high gain can be obtained in the reading direction D2 of the RFID tag 2 while downsizing. Can be
Since the feeding element 17a and the parasitic element 17b are built in the case 4, the size can be reduced.

(Second Embodiment)
FIG. 13 shows a second embodiment of the present invention. The difference from the previous embodiment is that the shape and arrangement of the parasitic elements are changed. The same parts as those of the above-described embodiment are denoted by the same reference numerals and description thereof is omitted, and different parts will be described below.

  As shown in FIG. 13A, an inverted U-shaped (C-shaped) parasitic element 17d in which U-shaped parasitic elements 17b are arranged in opposite directions may be provided. ), A parasitic element 17e including a matching element 17ea may be disposed. When the parasitic element 17e includes the matching element 17ea, the parasitic element 17e may include an impedance element having an inductor property.

  In this case, if the matching element 17ea having an inductor property is arranged near the center of the line segment 17eb of the parasitic element 17e through which a large amount of current flows, the effective length is increased even if the matching element 17ea has a small inductor value. The effect that it can be obtained. In order to meet the recent demand for miniaturization, the matching element 17ea may be provided at the end of the U-shape. That is, the parasitic element 17e includes a line segment portion 17eb that extends linearly and a bent portion 17ec that is bent at both ends of the line segment portion 17eb, but the bent portion 17ec is formed linearly long. This is because, depending on the design of the case 4, the shorter one of the bent portions 17 ec may be easily housed in the case 4.

  Therefore, in order to give priority to the degree of freedom of design of the case 4 and facilitate the storage in the case 4, it is preferable to arrange the matching element 17ea at the bent portion 17ec while shortening the bent portion 17ec. Then, the bending part 17ec can be reduced in size and can be comprised in a substantially linear shape. Thereby, it becomes possible to flexibly respond to the shape requirement of the case 4.

  As shown in FIG.13 (c), you may arrange | position the parasitic element 17f provided with the bending part 17fa. The bent portion 17fa is provided at a bent portion at both ends of the line segment portion 17fb extending linearly. In this manner, even if the parasitic elements 17d to 17f are provided on the sides of the feeder element 17a, substantially the same effects as those of the above-described embodiment can be obtained.

(Other embodiments)
The present invention is not limited to the above embodiment, and for example, the following modifications or expansions are possible.
In the above-described embodiment, the present invention is applied to the reader 1 that reads the barcode B. However, the reader 1 further reads other information codes such as other one-dimensional codes or two-dimensional codes such as QR codes (registered trademark). It may be applied. Although the mode in which the radio wave communication mechanism 5 performs communication processing with the RFID tag 2 using the UHF band is shown, the present invention may be applied to a mode in which communication is performed using another band such as a microwave band.

The reader 1 may be applied to a reader that can write data to the RFID tag 2 regardless of only reading data stored in the RFID tag 2.
If the shape of the parasitic element 17b is formed in a U shape, the relative disposition relationship between the parasitic element 17b and the feeder element 17a is not limited to the positional relationship described in the above embodiment. As long as the parasitic element 17b is located in the vicinity of the reading port 4a on the reading port 4a side from the installation position of the feeding element 17a, the parasitic element 17b may be disposed at any position.
Either one or both of the feeding element 17 a and the parasitic element 17 b may be installed outside the case 4.

  In the drawings, 1 is a reader, 2 is an RFID tag, 3 is a tag side antenna, 4 is a case, 4a is a reading port, 5 is a radio wave communication mechanism, 6 is an optical information reading mechanism, 7 is a control circuit, 8 is a display unit, 9 is an operation unit, 10 is a battery pack, 11 is a printed wiring board, 12 is an image sensor, 13 is a camera unit, 14 is a cable, 15 is an imaging lens, 16 is an illumination light source, 17 is a reader antenna, and 17a is a power supply. Elements, 17aa is an antenna surface, 17ab is a ground surface, 17b to 17f are parasitic elements, 17eb is a line segment, 17ec is a bend, 17fa is a bend, 17fb is a line segment, 18 is a transmission circuit, 19 is A receiving circuit is shown.

Claims (8)

An optical information reading mechanism for optically reading an information code through a reading port;
A radio wave communication mechanism for reading information stored in the RFID tag via a radio wave signal,
The radio wave communication mechanism has a ground plane and an antenna surface and is formed by a feeding element by a patch antenna disposed at a different location from the optical information reading mechanism and a U-shaped linear member, and a reading port of the optical information reading mechanism A reader comprising: a parasitic element positioned at a side edge and disposed so as to surround the reading port. When the radio wave communication mechanism communicates with the RFID tag by a radio wave signal of wavelength λ,
2. The reader according to claim 1, wherein the parasitic element is disposed at a distance in a range of [lambda] / 60 to [lambda] / 10 from the ground plane in a direction perpendicular to the ground plane of the patch antenna. . When the radio wave communication mechanism communicates with the RFID tag by a radio wave signal of wavelength λ,
The parasitic element is disposed at a distance in a range of 0 to λ / 15 from an end of the ground plane in a horizontal direction of the ground plane of the patch antenna. The reader described.   4. The reader according to claim 1, wherein the parasitic element includes a matching element.   The parasitic element is formed in the U-shape including a linearly extending line segment part and a bent part positioned at both ends of the line segment part and positioned at the bent part. The reader according to any one of claims 1 to 4, further comprising a bent portion bent in a zigzag manner.   The parasitic element is formed in the U-shape including a linearly extending line segment part and bent parts positioned at both ends of the line segment part, and the line segment part of the patch antenna. 6. The reader according to claim 1, wherein the reader is disposed on the ground surface side.   The parasitic element is molded into the U-shape including a line segment part and a bent part that is bent at both ends of the line segment part, and the bent part is on the ground plane side of the patch antenna. The reader according to any one of claims 1 to 5, wherein the reader is disposed in close proximity and the line segment is disposed away from the ground plane of the patch antenna.   The reader according to claim 1, wherein both the feeding element and the parasitic element are built in.

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