JP2015060442A - Rfid reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an RFID reading device which can realize a high gain of an antenna.SOLUTION: A non-contact communication unit 30 comprises an RFID module substrate 31 for performing non-contact communication with an RFID tag 50 through an antenna 32. The RFID module substrate 31 is connected to a main substrate 20 and is connected through a coaxial cable 33 to the antenna 32 facing through a predetermined gap. A capacity coupling wiring unit 33a of the coaxial cable 33 for connecting the ground of the RFID module substrate 31 and the ground of the antenna 32 is arranged along the main substrate 20.

Description

  The present invention relates to an RFID reader.

  2. Description of the Related Art Conventionally, as a technique related to an RFID reader that reads an RFID tag through radio waves transmitted and received via an antenna, a portable communication terminal shown in Patent Document 1 is known. In this portable communication terminal, a sheet-like soft magnetic wave absorber covering the non-contact type coil antenna is provided in a housing in order to improve both the communication performance of the non-contact type coil antenna and the overall size and thickness. It is fixed on a sheet-like flexible substrate disposed on the inner surface of the body. As a result, the electromagnetic coupling between the shield case, metal part, metal body or substrate constituting the electronic component and the non-contact type coil antenna is prevented by the soft magnetic wave absorber, thereby improving the communication performance of the non-contact type coil antenna. I am trying.

JP 2004-153463 A

  However, in recent years, it has been desired to further increase the gain of the antenna, for example, by improving the reading accuracy during wireless communication and widening the communication distance. In some cases, it may be insufficient to increase the gain. In addition, when a soft magnetic wave absorber is separately provided as in Patent Document 1, not only does the manufacturing cost increase, but it may be a factor that hinders further downsizing depending on the installation location. Problems also arise.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an RFID reader capable of increasing the gain of an antenna.

In order to achieve the above object, the invention described in claim 1 is an RFID reader (10) that reads an RFID tag (50) through radio waves transmitted and received via an antenna (32). The RFID module substrate (31), other substrates (20, 20a) provided with a ground, the ground wire (33) connecting the ground of the RFID module substrate and the ground of the antenna, and the RFID module substrate A housing (11) that accommodates the other substrate and the ground wire, wherein at least a part (33a) of the ground wire protrudes outside the RFID module substrate, and the other wire is placed on the other substrate. It arrange | positions so that it may follow along.
In addition, the code | symbol in each said parenthesis shows the correspondence with the specific means as described in embodiment mentioned later.

  According to the first aspect of the present invention, at least a part of the ground line connecting the ground of the RFID module board and the ground of the antenna (hereinafter also referred to as a capacitive coupling wiring section) protrudes outside the RFID module board and It arrange | positions so that it may follow with respect to a board | substrate. As a result, the capacitive coupling wiring section and the ground of another substrate are capacitively coupled, so that the other substrate can be used as a virtual ground for the antenna, and the high gain of the antenna can be achieved without hindering the downsizing of the housing. Can be achieved.

  In the invention of claim 2, the ground line is arranged so that the wiring direction of the capacitive coupling wiring portion is along the longitudinal direction of the casing. Thereby, the gain of the antenna in the longitudinal direction of the casing is improved. Since the casing holds the grip portion formed on one side in the longitudinal direction and the other side in the longitudinal direction is directed to the RFID tag when reading the RFID tag, the antenna in the longitudinal direction of the casing as described above. As a result, the gain of the antenna can be increased in accordance with the actual reading situation. In addition, since the wiring is performed so that the capacitive coupling wiring portion of the ground wire extends in the longitudinal direction of the housing, for example, the capacitance is compared with the case where the capacitive coupling wiring portion is extended in the lateral direction of the housing. The length of the coupling wiring portion along the other substrate can be easily increased, and the gain of the antenna can be reliably increased.

  In the invention of claim 3, the length of the electrical connection path of the cable for electrically connecting the electronic component and the ground of another substrate is set to about ½ of one wavelength of the radio wave. Here, about 1/2 of one wavelength of the radio wave is a value having a certain width before and after the center of 1/2 of one wavelength of the radio wave.

  For this reason, even when a current is induced in the cable due to radio wave radiation from the antenna, the current approaches zero at both ends of the cable, so that the current induced in the electronic component can be reduced. As a result, radio wave radiation from the electronic component is suppressed, and a decrease in gain of the antenna can be prevented.

  In the invention of claim 4, the ground wire is configured as an outer conductor of a coaxial cable connecting the RFID module substrate and the antenna. As described above, even if the capacitive coupling wiring portion of the coaxial cable having the ground wire as the outer conductor is arranged along the other substrate, the capacitive coupling wiring portion and the ground of the other substrate are not connected. By capacitive coupling, another substrate can be used as a virtual ground of the antenna, and a high gain of the antenna can be achieved.

  In the invention of claim 5, the other substrate is configured as a main substrate connected to the RFID module substrate. For this reason, since the RFID module substrate is disposed close to the main substrate, the distance between the capacitive coupling wiring portion and the ground of the main substrate can be easily reduced, and the effect of capacitive coupling is further enhanced. Can do.

It is a figure which shows the structure outline | summary of the RFID reader which concerns on 1st Embodiment. It is a block diagram which illustrates the electric constitution of a RFID reader. It is explanatory drawing which shows the positional relationship of a main board | substrate and a coaxial cable. It is explanatory drawing which shows the principal part of the RFID reader in 2nd Embodiment. It is explanatory drawing which illustrates notionally the electric current induced by the cable connected to a vibrator. It is explanatory drawing which illustrates notionally the electric current distribution induced by the radiation | emission of the electromagnetic wave from an antenna. It is explanatory drawing which shows the modification of the positional relationship of another board | substrate and a coaxial cable.

[First Embodiment]
Hereinafter, a first embodiment in which an RFID reader according to the present invention is embodied will be described with reference to the drawings. 1A and 1B are diagrams showing an outline of the configuration of an RFID reader 10 according to the first embodiment. FIG. 1A is a front view and FIG. 1B is a side view. FIG. 2 is a block diagram illustrating an electrical configuration of the RFID reader 10.

  An RFID reader 10 shown in FIGS. 1A and 1B is configured as a portable information terminal that is carried by a user and used in various places, and uses radio waves transmitted and received via an antenna as a medium. In addition to the function as a wireless tag reader for reading information stored in the RFID tag (wireless tag) 50, it has a function as an information code reader for reading an information code such as a barcode or a two-dimensional code. It has a configuration that can be performed.

  As shown in FIGS. 1 (A) and 1 (B), an RFID reader 10 has a longitudinal casing configured by assembling an upper case 11a and a lower case 11b formed of a synthetic resin material such as ABS resin. The body 11 forms an outer shell. The upper case 11a is provided with a key operation unit 25 such as function keys and numeric keys operated when inputting predetermined information, a display unit 24 for displaying predetermined information, and the like. The lower case 11b has a reading port 12 that opens downward. In the following description, the side of the casing 11 on which the key operation unit 25 and the like are arranged and configured as the gripping unit is one side in the longitudinal direction, and the side on which the display unit 24 and the reading port 12 are arranged is the other side in the longitudinal direction. This will be described as a side.

Next, functions provided in the RFID reader 10 will be described.
As shown in FIGS. 1 and 2A, various components (such as various electrical components) are mounted and accommodated in a main substrate 20 or the like in a housing 11 of the RFID reader 10, and this main substrate is accommodated. 20 includes a control unit 21 that controls the entire RFID reader 10. The control unit 21 is composed mainly of a microcomputer, has a CPU, a system bus, an input / output interface, and the like, and constitutes an information processing apparatus together with the memory 22. The control unit 21 is connected to an LED 23, a display unit 24, a key operation unit 25, a vibrator 26, a buzzer 27, an external interface 28, and the like.

  The key operation unit 25 is configured to give an operation signal to the control unit 21, and the control unit 21 receives the operation signal and performs an operation according to the content of the operation signal. Further, the LED 23, the display unit 24, the vibrator 26 and the buzzer 27 are configured to be controlled by the control unit 21, and each operate in response to a command from the control unit 21. The external interface 28 is configured as an interface for performing data communication with an external device or the like, and is configured to perform communication processing in cooperation with the control unit 21. In addition, a power supply unit 29 is provided in the housing 11, and power is supplied to the control unit 21 and various electrical components by the power supply unit 29 and the battery 29 a.

The non-contact communication unit 30 and the information code reading unit 40 are connected to the control unit 21.
First, the non-contact communication part 30 is demonstrated using FIG. 2 (B) and FIG.
The non-contact communication unit 30 includes an RFID module substrate 31 for performing non-contact communication with the RFID tag 50 via the antenna 32. The RFID module substrate 31 is connected to the main substrate 20 and is connected to an antenna 32 opposed via a coaxial cable 33 via a predetermined gap. The antenna 32 is configured as a C-type antenna or a loop antenna configured by winding a conducting wire many times.

  In the coaxial cable 33, the inner conductor functions as a signal line that connects the RFID module substrate 31 and the antenna 32, and the outer conductor functions as a ground line that connects the ground of the RFID module substrate 31 and the ground of the antenna 32. Are wired like so. The arrangement of the RFID module substrate 31 and the coaxial cable 33 will be described in detail later.

  The non-contact communication unit 30 communicates by radio waves (electromagnetic waves) with the RFID tag 50 in cooperation with the antenna 32 and the control unit 21 to read data stored in the RFID tag 50 or to the RFID tag 50. It functions to write data.

  The non-contact communication unit 30 is configured as a circuit that performs transmission using a known radio wave system, and includes an oscillator 34, a modulator 35, a demodulator 36, and the like, as schematically shown in FIG. It will be. The RFID module substrate 31 of the non-contact communication unit 30 is provided with other known configurations (for example, an amplifier, a filter circuit, a matching circuit, etc.), but these are not shown in FIG. Omitted.

Next, the information code reading unit 40 will be described with reference to FIG.
The information code reading unit 40 functions to optically read the information code. As shown in FIG. 2C, the information code reading unit 40 includes a light receiving sensor 43 including a CCD area sensor, an imaging lens 42, a plurality of LEDs, It has a configuration including an illumination unit 41 composed of a lens and the like, and functions to read an information code C (bar code or two-dimensional code) attached to a reading target R in cooperation with the control unit 21. To do.

  When reading is performed by the information code reading unit 40, first, the illumination light Lf is emitted from the illumination unit 41 that has been instructed by the control unit 21, and the illumination light Lf passes through the reading port 12 (see FIG. 1B). The reading object R is irradiated therethrough. The reflected light Lr reflected by the illumination light Lf by the information code C (bar code or two-dimensional code) is taken into the apparatus through the reading port 12, and is received by the light receiving sensor 43 through the imaging lens. The The imaging lens 42 disposed between the reading port 12 and the light receiving sensor 43 is configured to form an image of the information code C on the light receiving sensor 43, and the light receiving sensor 43 is an image of the information code C. The light reception signal corresponding to the is output. The light receiving signal output from the light receiving sensor 43 is stored as image data in the memory 22 (FIG. 2A) and used for decoding processing for acquiring information included in the information code C. The information code reading unit 40 is provided with an amplifying circuit for amplifying the signal from the light receiving sensor 43 and an AD converting circuit for converting the amplified signal into a digital signal. Is omitted.

Next, a characteristic configuration of the RFID reader 10 according to the present embodiment will be described with reference to FIG. FIG. 3 is an explanatory diagram showing the positional relationship between the main board 20 and the coaxial cable 33.
In this embodiment, in order to improve the gain of the antenna 32, the coaxial cable 33 is arranged so that a part thereof is along the main board 20.

  Specifically, as shown in FIG. 1, the main board 20 is accommodated in the casing 11 so that the longitudinal direction thereof coincides with the longitudinal direction of the casing 11. As shown in FIG. 3, the RFID module substrate 31 is disposed so as to be parallel to a portion on the other side in the longitudinal direction of the main substrate 20 (upper side in FIG. 3).

  Further, the coaxial cable 33 is folded back at a position away from both substrates from an edge on one side in the longitudinal direction of the RFID module substrate 31 (lower side in FIG. 3) to an edge on one side in the longitudinal direction of the antenna substrate on which the antenna 32 is provided. Have been drawn around. In particular, a part of the coaxial cable 33 protruding from the RFID module substrate 31 (hereinafter also referred to as a capacitive coupling wiring portion 33a) is parallel to the substrate surface of the main substrate 20 and is in the longitudinal direction of the main substrate 20 It arrange | positions along (up-down direction of FIG. 3).

  In the present embodiment, the length of the capacitive coupling wiring portion 33a is set to be 1 / 8λ or more when one wavelength of the radio wave is λ. As can be seen from FIG. 3, the length of the main substrate 20 in the longitudinal direction is set to be sufficiently longer than the turning point of the capacitive coupling wiring portion 33 a extending from the RFID module substrate 31.

  For this reason, the capacitive coupling wiring portion 33a of the coaxial cable 33 is arranged so as to be close to and parallel to the main substrate 20, and the ground line of the capacitive coupling wiring portion 33a and the ground of the main substrate 20 are arranged. Are in an arrangement state capable of capacitive coupling.

  When radio waves are radiated from the antenna 32 in such a state, the ground line of the capacitive coupling wiring portion 33a of the coaxial cable 33 and the ground of the main board 20 are capacitively coupled. It will be used as a virtual ground. For this reason, the gain of the antenna 32 in the longitudinal direction of the main board 20, that is, in the longitudinal direction of the housing 11 is improved.

  For example, in the RFID reader 10 that uses the 900 MHz band (one wavelength λ = 320 mm of radio waves), from the edge on one side in the longitudinal direction of the RFID module substrate 31 to the edge on one side in the longitudinal direction of the antenna substrate on which the antenna 32 is provided. When the length of the coaxial cable 33 is about 110 mm, the gain of the antenna 32 in the longitudinal direction of the housing 11 can be improved by 2 dB. The gain of the antenna 32 in this direction was further improved when the coaxial cable 33 was lengthened. That is, when the length of the coaxial cable 33 (the length of the capacitive coupling wiring portion 33a along the longitudinal direction of the main board 20) is increased, the gain of the antenna 32 in the longitudinal direction of the housing 11 can be further improved.

  As described above, in the RFID reader 10 according to the present embodiment, the capacitive coupling wiring portion 33 a of the coaxial cable 33 that connects the ground of the RFID module substrate 31 and the ground of the antenna 32 is outside the RFID module substrate 31. It protrudes and is arranged along the main board 20. As a result, the main board 20 can be used as a virtual ground of the antenna 32 by capacitively coupling the ground line of the capacitive coupling wiring portion 33a and the ground of the main board 20 to increase the gain of the antenna 32. Can do.

  In particular, since the coaxial cable 33 is arranged so that the wiring direction of the capacitive coupling wiring portion 33 a is along the longitudinal direction of the housing 11, the gain of the antenna 32 in the longitudinal direction of the housing 11 is improved. The housing 11 grips a grip portion formed on one side in the longitudinal direction (side on which the key operation unit 25 or the like is disposed), so that when reading the RFID tag 50, the other side in the longitudinal direction (display unit 24). Since the gain of the antenna 32 in the longitudinal direction of the housing 11 is improved as described above, the gain of the antenna 32 in accordance with the actual reading situation is increased. Can be achieved. In addition, since wiring is performed so that the capacitive coupling wiring portion 33a of the coaxial cable 33 extends in the longitudinal direction of the casing 11, for example, the capacitive coupling wiring portion 33a extends in the short direction of the casing 11. In comparison, the length of the capacitive coupling wiring portion 33a along the main substrate 20 can be easily increased, and the gain of the antenna 32 can be reliably increased.

  The capacitive coupling wiring portion 33a is not limited to be disposed along the longitudinal direction of the main substrate 20 (housing 11), but may be disposed along the direction in which the gain is desired to be improved.

  Further, the ground line connecting the ground of the RFID module substrate 31 and the ground of the antenna 32 is not limited to being configured as an outer conductor of the coaxial cable 33, and is configured as, for example, a dedicated ground line provided separately from the signal line. May be. In this case, it is possible to increase the gain of the antenna 32 by arranging a part of the dedicated ground line along the main substrate 20 as the capacitive coupling wiring portion 33a.

[Second Embodiment]
Next, an RFID reader according to the second embodiment will be described with reference to FIGS. FIG. 4 is an explanatory diagram illustrating a main part of the RFID reader 10 according to the second embodiment. FIG. 5 is an explanatory diagram for conceptually explaining the current induced in the cable 26 a connected to the vibrator 26. FIG. 6 is an explanatory diagram conceptually illustrating the current distribution induced by the radiation of the radio wave from the antenna 32. 5 and 6 show a state where the cable 26a is linearly extended for convenience of explanation.

  The second embodiment is mainly different from the RFID reader according to the first embodiment in that the length of a cable or the like connected to the main board 20 is adjusted to prevent the gain of the antenna 32 from being lowered. . Therefore, substantially the same components as those of the RFID reader according to the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  When electronic components (including metal components) that are electrically connected to the main board 20 via a cable or the like are disposed around the antenna 32, a current flows through the cable or the like due to the emission of radio waves from the antenna 32. Is induced. In this case, a current also flows through the electronic component connected to the cable or the like, and a radio wave corresponding to the current value is radiated from the electronic component, which causes a decrease in the gain of the antenna 32. There is.

  Therefore, in the present embodiment, the cable for electrically connecting the electronic component and the ground of the main board 20 has an electrical connection path length of about ½ of one wavelength λ of the radio wave (around λ around). Is set to a certain width). In the present embodiment, for example, the electrical connection path length of the cable 26a that connects the vibrator 26 disposed in the vicinity of the antenna 32 and the ground of the main board 20 is set to 1 / 2λ.

  For this reason, even when the current I3 is induced in the cable 26a due to the emission of radio waves from the antenna 32, the current approaches 0 at both ends of the cable 26a as illustrated in FIGS. Become. As a result, the current induced in the vibrator 26 can be reduced to 0 or small, the radio wave radiation from the vibrator 26 can be suppressed, and the gain reduction of the antenna 32 can be prevented. In FIG. 6, the current flowing through the antenna 32 is denoted by reference numeral I1, and the current flowing through the main board 20 is denoted by reference numeral I2.

  Note that the electrical connection path length of the cable 26a connected to the vibrator 26 is not limited to about ½λ, and the electronic component and the main board that are arranged in the housing 11 in the vicinity of the antenna 32 Even if the electrical connection path length of the cable connecting the 20 grounds is set to about ½λ, the gain of the antenna 32 can be prevented from being lowered.

In addition, this invention is not limited to said each embodiment, For example, you may actualize as follows.
(1) In the first embodiment, the capacitive coupling wiring portion 33 a is not limited to be disposed along the main substrate 20, but is along another substrate having a ground accommodated in the same housing 11. May be arranged as follows. In this case, the ground line of the capacitive coupling wiring portion 33a and the ground of another substrate are capacitively coupled, so that the other substrate can be used as a virtual ground of the antenna 32, and the gain of the antenna 32 is increased. Can be planned.

(2) In the second embodiment, a substrate to which electronic components such as the vibrator 26 are connected via a cable is not limited to the main substrate 20, but may be another substrate having a ground housed in the same housing 11. It may be connected.

(3) FIG. 7 is an explanatory view showing a modification of the positional relationship between the other substrate 20a and the coaxial cable 30. FIG.
Other substrates (including the main substrate 20) described above are sufficiently more than the turning point of the capacitive coupling wiring portion 33a extending from the RFID module substrate 31 so that the capacitive coupling wiring portion 33a is close to and parallel to the parallel coupling portion 33a. The antenna 32 can be increased in gain by being arranged so that the ground line such as the coaxial cable 33 extends along even a part thereof.

Specifically, for example, as illustrated in FIG. 7, the length of the other substrate 20 a in the longitudinal direction (vertical direction in FIG. 7) is the folding back of the capacitive coupling wiring portion 33 a extending from the RFID module substrate 31. It is set to be shorter than the point.
Even if it does in this way, although gain improvement becomes smaller than 1st Embodiment, the ground line of the other board | substrate 20a and the ground of the main board | substrate 20 carry out capacitive coupling, and the other board | substrate 20a is made into the virtual ground of the antenna 32. The gain of the antenna 32 can be increased.

10. RFID reader 20 ... Main board (other boards)
20a ... Other board 30 ... Non-contact communication part 31 ... RFID module board 32 ... Antenna 33 ... Coaxial cable 33a ... Wiring part for capacitive coupling 50 ... RFID tag

Claims (5)

An RFID reader that reads an RFID tag through radio waves transmitted and received via an antenna,
An RFID module substrate;
With another substrate on which a ground is provided;
A ground line connecting the ground of the RFID module substrate and the ground of the antenna;
A housing for housing the RFID module substrate, the other substrate, and the ground wire;
With
The RFID reader is characterized in that at least a part of the ground line protrudes outside the RFID module substrate and is arranged along the other substrate.   2. The RFID reader according to claim 1, wherein the ground line is disposed such that at least a part of the wiring direction is along a longitudinal direction of the housing. A cable for electrically connecting a part of electronic components housed in the housing and the ground of the other board;
The RFID reader according to claim 1 or 2, wherein a connection path length of the cable is set to about ½ of one wavelength of the radio wave.   4. The RFID reader according to claim 1, wherein the ground line is an outer conductor of a coaxial cable that connects the RFID module substrate and the antenna. 5.   5. The RFID reader according to claim 1, wherein the other substrate is a main substrate connected to the RFID module substrate. 6.

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