JP5012662B2 - Portable information terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile information terminal extending a long distance communication range of an antenna for RFID using a metal holder, while suppressing an increase in its lateral dimension. <P>SOLUTION: The metal holder 8 is arranged behind the antenna 12 for RFID at a point of 15-45 mm distance with a feed point 12c of the antenna 12 for RFID in a horizontal direction. The metal holder 8 is formed in the shape of a ring having cavities 8a in its inside. Thereby, increase in the lateral dimension of the holder 8 is suppressed, while the holder 8 is functioned effectively as a reflector. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a portable information terminal including an RFID antenna in a 950 MHz band that communicates with an RFID tag, and a metal holder for holding an electronic device.

In a portable RFID reader / writer using the 950 MHz band, the RFID antenna is affected by a metal holder for holding an electronic device (optical information reading module, LCD, etc.), and the communication distance with the RFID tag There is a problem that becomes shorter.
If the distance between the antenna and the holder is increased in order to avoid such a problem, the portable RFID reader / writer is increased in size.
On the other hand, there has been proposed an RFID antenna that improves the communication distance by devising the arrangement of the metal body to function as a reflector of the antenna (see Patent Document 1). Therefore, the metal holder can function as a reflector for the RFID antenna.
JP 2000-77928 A

  In Patent Document 1, only the result of substantially the same plane is disclosed as the distance between the antenna and the metal body, and the positional relationship between the antenna and the holder is restricted as in a portable RFID reader / writer. Even if the configuration of Patent Document 1 is applied as it is, the effect as a reflector is not always obtained.

  Further, when the metal body functions as an antenna reflector, it is necessary to have a length of at least λ × 0.6 (λ / 2 or more, but λ × 0.6 with allowance). For this reason, when the communication frequency is in the 950 MHz band, the communication wavelength λ is about 316 mm, so the length of the metal holder (the length of the part parallel to the RFID antenna) is required to be about 190 mm or more, In the portable RFID reader / writer, there is no space that can ensure the length of the portable RFID reader / writer in a straight line.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a portable information terminal capable of suppressing lateral dimensions while increasing the communication distance of an RFID antenna using a metal holder. Is to provide.

  When the metal holder is arranged close to the RFID antenna, the RFID antenna is affected by the metal holder, and the communication distance by the RFID antenna varies. This fluctuation may be longer or longer than the communication distance, and varies depending on the shape of the RFID antenna, so that optimum conditions are obtained through experiments.

  From the experimental results, under the condition that the metal holder is provided close to the RFID antenna, the condition that the communication distance is longer than when there is no holder is It has been found that the distance in the front-rear direction is 15 to 45 mm, which is disposed substantially in front of the RFID antenna, and that the holder has an annular shape and a hollow inside.

In addition, in order for the holder to function as a reflector for the RFID antenna when the communication frequency is in the 950 MHz band, the horizontal dimension of the holder is required to be about 190 mm or more. While suppressing, the holder can function effectively as a reflector.
Therefore, according to the invention of claim 1, since the metal holder is configured to satisfy the above-described conditions, the communication distance can be increased.

Hereinafter, an embodiment in which the present invention is applied to a portable RFID reader / writer capable of both reading and writing data of an RFID tag and reading optical information such as a barcode and a two-dimensional code will be described with reference to the drawings. explain.
2 is a longitudinal side view showing a schematic configuration of a portable RFID reader / writer, FIG. 3 is an exploded view thereof, and FIG. 4 is a bottom view showing an internal configuration, and shows only the configuration related to the present invention. A portable RFID reader / writer (hereinafter abbreviated as a reader / writer) 1 is configured by storing a control unit 5 in a positioning state in a main body 4 composed of an upper case 2 and a lower case 3.

  A reading port 6 for reading optical information is formed at the front end surface of the main body 4 (lower case 3). On the upper surface of the base end (grip) of the main body 4 (upper case 2), there are a plurality of operation keys (not shown) such as a power switch, a notification LED, a speaker, numeric keys and function keys. A key operation unit 7 is provided. The main body 4 is provided with a trigger switch for reading instruction (not shown).

  The control unit 5 is configured by screwing a main control board 9, an RFID control board 10, and an optical information reading unit 11 on the lower surface of a metal holder 8 made of magnesium. An RFID antenna 12 is connected to the RFID control board 10 by a coaxial cable 13. The holder 8 is formed in a container shape, and a liquid crystal display unit (corresponding to an electronic device) (not shown) is accommodated on the upper surface thereof and connected to the main control board 9.

The main control board 9 is mainly composed of a microcomputer, and controls a notification LED, a speaker, a liquid crystal display unit, and the like according to input of operation signals from a trigger switch, a key operation unit 7 and the like. The main body 4 is also provided with a battery and a power supply unit serving as a power source, an external interface for performing data communication with the outside (host device), and the like.
The RFID control board 10 outputs a transmission signal to the RFID antenna 12 in accordance with a command from the main control board 9 and performs data communication with an RF tag (not shown) to read data. Write.

  The optical information reading unit 11 includes a CCD area sensor (not shown), an imaging lens, an illumination unit including a plurality of LEDs and lenses, and the like. The illumination unit irradiates illumination light to a label that is a reading target disposed forward through the reading port 6. Reflected light from the optical information (barcode or two-dimensional code) printed on the label enters through the reading port 6 and forms an image on the CCD area sensor through the imaging lens, thereby obtaining optical information image data. Read and read (decode) data.

  The RF tag is attached to an article such as a product, and includes an RFID chip that includes a tag-side antenna for performing communication with the RFID antenna, and that holds data and generates a response signal. It is configured with. The RFID chip is a rectifying / smoothing circuit for obtaining operating power from a transmission signal, a CPU for controlling communication, a modulation / demodulation circuit for modulating / demodulating transmission / reception signals, a ROM for storing operation programs, and a reading for storing data. A programmable EEPROM or the like is formed as a one-chip IC.

  As described above, the reader / writer 1 can perform optical reading of optical information by the optical information reading unit 11 and communication (reading and writing of data) between the RFID tag and the RF tag. Yes.

  The RFID antenna 12 is a dipole antenna made of a flexible substrate, and includes a symmetrical difolded dipole 12a and a folded portion 12b formed at the center of the folded dipole 12a as shown in FIG. The feeding point 12c provided on the folded portion 12b is connected to the RFID control board 10 via the coaxial cable 13 shown in FIG. As shown in FIG. 1A, the feeding point 12 c is configured at the center of the main body 4. The RFID antenna 12 is housed along the inner surface of the front end of the upper case 2 and radiates a 950 MHz band electromagnetic wave forward when a transmission signal is given from the RFID control board 10.

  FIG. 1 schematically shows the positional relationship between the RFID antenna 12 and the holder 8 in the above configuration. As shown in FIG. 1, when the metallic holder 8 is arranged close to the rear of the RFID antenna 12, the RFID antenna 12 is affected by the metallic holder 8, and the RFID antenna 12. The communication distance of fluctuates. This variation may be short or long in communication distance. That is, the metal holder 8 functions as a reflector of the RFID antenna 12, and the effect as the reflector varies greatly depending on the distance between the RFID antenna 12 and the holder 8 or the shape of the holder 8. .

Therefore, the effect of the distance between the RFID antenna 12 and the holder 8 or the shape of the holder 8 on the radiated power from the RFID antenna 12 was examined by experiments.
FIG. 5 schematically shows the experimental setup. An RFID antenna 12 having a lateral dimension of 113 mm is used, a receiving antenna 14 for receiving a radiation signal from the RFID antenna 12 having a lateral dimension of 150 mm, the RFID antenna 12 and the holder 8 The change in the intensity of the radiated power received by the receiving antenna 14 was examined according to the distance D between the two. In this case, the RFID antenna 12, the receiving antenna 14, and the holder 8 are set so that their centers coincide.

  Here, the distance D between the RFID antenna 12 and the holder 8 is a distance in the front-rear direction between the feeding point of the RFID antenna 12 and the front end position of the holder 8. Further, the holder 8 is shifted in the height direction so as to have the same positional relationship as the actual product with respect to the RFID antenna 12. That is, the experiment was performed by shifting the holder 8 in the height direction by the approximate height dimension of the RFID antenna 12.

  As the holder, an actual product holder 8 actually used as a product as shown in FIG. 6 and comparison holders 15 and 16 as shown in FIGS. 7A and 7B were used. Each of the holders 8, 15 and 16 has a rectangular shape with a lateral dimension of 70 mm and a front-rear dimension of 100 mm, and the holders 8 and 15 are formed in an annular shape in the present invention. The term “annular” in this case means that the outer peripheral path has a shape that makes a round. The working product holder 8 has a plurality of rectangular or triangular cavities 8a formed therein. The comparison holder 15 has one large rectangular cavity 15a formed inside. On the other hand, the holder 16 is a holder having no cavity inside.

  FIG. 8 shows the experimental results and shows the relationship between the holder-antenna distance D and the radiated power. From this experimental result, when the holders 8 and 15 are gradually approached to the RFID antenna 12, the radiation power starts to increase from about 50 mm in any of the holders 8 and 15, and reaches a peak at 20 to 40 mm. It has been found that sufficiently high radiation power can be obtained at ˜45 mm. It was also found that the radiated power was higher in the working product holder 8 than in the comparison holders 15 and 16 over the entire area. Also, the holders 8 and 15 with cavities are less effective than the holder 16 without cavities when the holder 16 without cavities is close to the RFID antenna 12 within 30 mm. The hollow holders 8 and 15 have a high radiation power of 15 to 45 mm. Therefore, although high radiated power can be obtained, the weight of the portable information terminal can be further reduced by providing the cavity.

  In addition, the length of the holder 8 (the length of the portion parallel to the RFID antenna 12) is about 316 mm in the case of the 950 MHz band. Even if the horizontal dimensions of the holders 8 and 15 were 70 mm, they could function sufficiently as a reflector. This is because the front end portions of the holders 8 and 15 that are parallel to the RFID antenna 12 function effectively as a reflector, but the side portions of the holders 8 and 15 are also reflected because the holders 8 and 15 are annular. This is because it effectively functions as the electrical path length of the vessel.

  In short, by incorporating the metal holder 8 into the main body 4 so that the distance in the front-rear direction with the RFID antenna 12 is 15 to 45 mm, the holder 8 can sufficiently function as a reflector to increase the communication distance. Distance can be achieved. Further, as the holder, a shape having a plurality of cavities 8a like the practical product holder 8 is more effective for increasing the radiated power, but has a single large cavity 15a like the comparative holder 15. Since the radiated power can be increased even in the case of an annular shape, it is not necessary to provide a plurality of cavities.

  Further, as shown in FIG. 9, an experiment was also conducted in the case where the positional relationship between the holder 8 and the RFID antenna 12 was changed. Experiments were performed when the holder 8 was shifted by the approximate height of the RFID antenna 12 and when the holder 8 was shifted 20 mm from the end face of the holder 8. The positional relationship of the holder 8 and the RFID antenna 12 other than the height direction is the same as that in FIG.

  As shown in FIG. 10, in the case of the arrangement relationship of FIG. 9C, the same high effect is obtained up to 40 mm, but the effect is reduced when closer to 40 mm. On the other hand, in the arrangement relationship shown in FIGS. 9A and 9B, a sufficient effect is obtained even at 15 to 45 mm. Therefore, the positional relationship in the height direction of the antenna is sufficiently effective even if it is shifted from the holder 8 by the height dimension of the RFID antenna 12.

  With such a positional relationship, the holder 8 side (the central portion of the portable information terminal) can be made thicker by the amount corresponding to the height difference of the RFID antenna 12, and the tip portion can be made relatively thin. Thus, the anti-drop impact can be mitigated by providing the tip portion with an inclined portion as viewed from the side and providing a roundness.

  According to such an embodiment, the metal holder 8 is disposed so that the distance in the front-rear direction between the RFID antenna 12 and the feeding point 12c of the RFID antenna 12 is 15 to 45 mm, substantially rearward of the RFID antenna 12, and Since it is configured in an annular shape having a plurality of cavities 8a on the inside, the horizontal dimension of the holder 8 is set to 1/2 of the communication wavelength while using the metal holder 8 to increase the communication distance of the RFID antenna 12. It is possible to sufficiently suppress the length.

(Other embodiments)
The material of the holder 8 is not limited to magnesium, and various metals can be used as long as they function as a reflector.
The holder 8 is not limited to a lateral dimension of 70 mm and a front-rear dimension of 100 mm.
The reading direction of the optical information is not limited to the forward direction but may be an oblique direction, or the optical information reading function may be omitted.

The top view of the antenna and holder for RFID in one embodiment of the present invention Vertical view of reader / writer Disassembled side view of reader / writer Bottom view of control unit Diagram showing experimental configuration Plan view showing the product holder Plan view showing a holder for comparison The figure which shows the relationship between the distance D between holder-antennas, and radiated power FIG. 5 equivalent diagram showing different arrangement relationships Equivalent to FIG.

Explanation of symbols

  In the drawings, 1 is a portable RFID reader / writer, 4 is a main body, 5 is a control unit, 8 is a holder, 9 is a main control board, 10 is an RFID control board, 11 is an optical information reading unit, and 12 is an RFID antenna. is there.

Claims (3)

A box-shaped body having a short side and a long side, and a thickness;
950 MHz band RFID antenna disposed along the short side at one end in the long side direction of the main body;
In a portable information terminal that is housed in the main body and includes a rectangular metal holder having a short side and a long side for holding an electronic device,
In the RFID antenna, a feeding point to which transmission power is fed is provided at the center in the horizontal direction of the main body,
The holder is disposed on the other end side away from the RFID antenna in the long side direction of the main body, the distance from the feeding point is 15 to 45 mm, and is formed in an annular shape having a hollow inside The portable information terminal is characterized in that the surface of the holder is disposed at a position higher than the RFID antenna by the height of the RFID antenna. The portable information terminal according to claim 1, wherein the holder has a short-side dimension that is ½ or less of a communication wavelength. The portable information terminal according to claim 2, wherein the holder has a short-side dimension of 70 mm.

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