JP2009044647A - Portable rfid-tag reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a portable RFID-tag reader which communicates with a desired RFID-tag even when a plurality of RFID-tags exist in a service area and prevents increase in size. <P>SOLUTION: In the portable RFID-tag reader, the intersecting angle made by a transmitting antenna 7 and a receiving antenna 8 is variable. The directivities of both antennas intersect by varying the intersecting angle and the range of the intersecting directivities varies. Therefore, the communication with the RFID-tag is established by moving both antennas 7, 8 so that the directivities of them are within the range. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a portable RFID tag reader that performs radio communication with an RFID tag by radio waves and reads information from the RFID tag.

In the RFID tag communication system, when an interrogation wave is emitted from a reader, the RFID tag receives the interrogation wave and receives power supply. When sufficient power is obtained, the RFID tag starts operation and returns a response wave. Recent readers, especially readers using radio waves in the UHF band (950 MHz band) can communicate with RFID tags several meters away, and the communication area is far and wide.
However, if there are multiple RFID tags in the communication area of the reader, the RFID tags in the communication area receive the interrogation wave and send back response waves. This causes a problem of reading.

In order to solve such a problem, in Patent Document 1, the interrogator is provided with two transmission antennas and one reception antenna, and a carrier wave having a frequency f1 is transmitted from one of the two transmission antennas. The interrogation wave modulated with data is transmitted as the first interrogation wave, and the non-modulated carrier wave of frequency f2 is transmitted as the second interrogation wave from the other transmission antenna, and the directivity of these two transmission antennas is variable. By controlling, only the RFID tag present at the point where the first interrogation wave and the second interrogation wave overlap is configured to return the response wave.
JP 2006-121156 A

  In the interrogator described in Patent Document 1, two transmission antennas and one reception antenna are required, and radio waves having different frequencies f1 and f2 must be transmitted from the two transmission antennas. , F2 is complicated. For this reason, the interrogator tends to be large in size and is difficult to apply to a portable RFID tag reader.

  The present invention has been made in view of the above circumstances, and even if there are a plurality of RFID tags in a communication area, it is possible to communicate with a desired RFID tag and to avoid an increase in size. It is to provide a tag reader.

  In the invention of claim 1, at least one of the transmitting antenna and the receiving antenna is movable, and by moving one of the antennas, the directivities of the two antennas intersect and the range of the directivity intersecting changes. Therefore, the RFID tag to be read can be communicated with the RFID tag by moving the antenna so that the directivity of both antennas is within the range where the directivity of both antennas intersects.

In the invention of claim 2, when the range where the directivity of the transmitting antenna and the receiving antenna intersects is changed, the communicated RFID tag is displayed in relation to the region where the intersecting directivity range is changed. When communicating with an RFID tag from which information is to be read, it becomes easy to move the antenna so that the RFID tag falls within a range where the directivities of both antennas intersect.
In the invention of claim 3, since the intensity of the radio wave transmitted from the transmission antenna can be changed, normal communication can be performed even with a distant RFID tag by increasing the radio field intensity.
In the invention of claim 4, since at least one of the transmission antenna and the reception antenna can change the plane of polarization, communication with the RFID tag is possible regardless of the attitude of the RFID tag. Further, if the polarization plane is set as desired, communication can be performed only with an RFID tag having a specific posture that matches the set polarization plane.

In the invention of claim 5, at least one of the transmission antenna and the reception antenna is constituted by a patch antenna, and the length and width of the antenna surface are dimensions of 1/2 to 1/32 of the wavelength of the transmitted / received radio wave. In the invention of claim 5, at least one of the transmission antenna and the reception antenna is composed of a Yagi antenna, and the length of the antenna element is 1/2 to 1/1 / wavelength of the transmission / reception radio wave. Since the size is determined to be 32, an antenna having good transmission / reception performance can be obtained.
As in the invention of claim 7, the transmitting antenna and the receiving antenna are configured by a patch antenna, a receiving antenna is configured by a Yagi antenna, or a transmitting antenna is configured by a Yagi antenna. A patch antenna can be used.

<First Embodiment>
A first embodiment of the present invention will be described below with reference to FIGS. As shown in FIGS. 1 and 4, a portable RFID tag reader (hereinafter simply referred to as a portable reader) 1 is provided with a main body 3 at the front part (upper part in the drawing) of a hand-held part 2. Various key switches 4 as operation means are provided on the upper surface side of the hand-held portion 2, and a display 5 made of, for example, a liquid crystal display is provided on the upper surface side of the main body portion 3. A touch panel 6 (see FIG. 7) is attached to the surface of the display screen of the display 5.

  A transmission antenna 7 and a reception antenna 8 are provided on the front surface of the main body 3. Both of these antennas 7 and 8 are composed of patch antennas, for example. As shown in FIG. 5, the patch antenna is provided with a conductor layer 10 a and an installation electrode layer 10 b which are antenna surfaces on both front and back surfaces of a printed board 9. In addition, 10c is a feeding point for connecting a feeding line. In this patch antenna, the vertical dimension a and the horizontal dimension b of the conductor layer 10a are both set to 1/2 to 1/32 of the wavelength of the radio wave used for communication with the RFID tag, and in this embodiment, set to 1/2. The performance is good.

  Such transmission antenna 7 and reception antenna 8 are provided in the main body 3 so as to be movable, for example, rotatable about a shaft 12 as shown in FIG. A swing link 13 having a guide hole 13a is connected to both the antennas 7 and 8, respectively. A support hole 13b is formed at one end of the swing link 13, and a rod 14 is slidably inserted into the support hole 13a. A slider 15 that is guided by the guide hole 13a and reciprocally moves is attached to one end of the rod 14 that protrudes into the guide hole 13a. The swing link 13 and the rod 14 are accommodated in the main body 3.

  A rack 16 is disposed in the reader 1 so as to be linearly movable in the front-rear direction. The other end of the rod 14 is rotatably connected to the front end of the rack 16. In addition, a motor 17 is disposed in the reader 1, and a pinion 18 attached to the rotating shaft meshes with the rack 16. Accordingly, the rack 16 is linearly reciprocated in the front-rear direction by the forward / reverse rotation of the motor 17, and as shown in FIGS. 6 (a) and 6 (b), the rack 15 is attached by the linear movement in the front-rear direction. The rod 14 swings the swing link 13 to change the crossing angle α between the transmitting antenna 7 and the receiving antenna 8.

  The mechanism for converting the linear movement of the rack 16 into the swing motion of the swing link 13 in order to change the crossing angle α between the antennas 7 and 8 in this way is called a swing link mechanism. The mechanism for converting the rotation of the motor 17 into the linear movement of the rack 16 (rotation-linear movement conversion mechanism) is referred to as a crossing angle adjusting mechanism. In this embodiment, the crossing angle α is a crossing angle of lines orthogonal to the antenna surfaces of both antennas 7 and 8.

  The transmission antenna 7 transmits an interrogation wave obtained by modulating a carrier wave with transmission data to the front of the reader 1. When the RFID tag receives the interrogation wave transmitted from the transmission antenna 7, it obtains operating power from the interrogation wave and returns a response wave. The reception antenna 8 responds from the RFID tag coming from the front of the reader 1. Receive. In this case, the patch antennas constituting the transmission antenna 7 and the reception antenna 8 have directivity as shown by broken lines in FIG. 1, for example, and the interrogation wave of the transmission antenna 7 is within the directivity range of the transmission antenna 7. Only the inside RFID tag receives. The RFID tag that has received the interrogation wave from the transmission antenna 7 returns a response wave, but the reception antenna 8 receives a response wave from the RFID tag that is within the directivity range. Therefore, when there are a plurality of RFID tags in front of the reader 1, the RFID tag that can be communicated with the reader 1 is a range where the directivity of the transmission antenna 7 and the directivity of the reception antenna 8 intersect. The range in which the directivities of both antennas 7 and 8 intersect is changed by changing the intersection angle α of both antennas 7 and 8.

  FIG. 7 is a block diagram showing an electrical configuration of the reader 1. As shown in FIG. 7, the reader 1 includes a device controller 19 that performs overall control of the reader 1 and a communication controller 20 that controls communication with the RFID tag. Both the control units 19 and 20 are mainly composed of a microcomputer, and include a CPU 21, a ROM 22, a RAM 23, and a bus (not shown) for connecting them.

  The device control unit 19 is connected to a key input unit 24 that outputs signals according to operations of the various key switches 4, the display 5, and the touch panel 6. On the other hand, a driver 25 that controls the operation of the motor 17 and a transmission / reception unit 26 that controls communication with the RFID tag are connected to the communication control unit 20. The control units 19 and 20 are connected to each other via the communication units 27 and 28, and can transmit and receive data to and from each other.

  The transmitting / receiving unit 26 is connected to the transmitting antenna 7 and the receiving antenna 8. The transmission / reception unit 26 outputs a carrier wave modulated by the transmission data given from the communication control unit 20 to the transmission antenna 7 at the time of transmission, and extracts data by demodulating the radio wave received from the RFID tag at the time of reception. The extracted data is given to the communication control unit 20. At the time of this transmission / reception, as the crossing angle α of both antennas 7 and 8 decreases, that is, the farther the overlapping range of directivity of both antennas 7 and 8, the greater the power of the carrier wave and the farther RFID tag is sufficient. Operating power is obtained. Further, when the reception antenna 8 receives the response wave, the communication control unit 20 acquires the crossing angle α between the antennas 7 and 8 at that time and the output of the carrier wave from the transmission antenna 7, and sends it to the device control unit 19. send. The device control unit 19 calculates the position of the RFID tag that communicated from the crossing angle α of both antennas 7 and 8 and the output power value.

  Next, the operation of the above configuration will be described with reference to the flowcharts of FIGS. When the articles 30 to which the RFID tags 29 are attached are scattered as shown in FIG. 3, the user's request is roughly the following two. The first is a case where an article 30a at a desired position is selected from many articles 30 and data is acquired from the RFID tag. The second case is a case where an article to which a specific RFID tag is attached is to be searched from among many articles 30.

  First, the outline of acquiring data from the RFID tag of an article at a desired position is as follows. The reader 1 communicates with the RFID tag 29 by changing the crossing angle α of both antennas 7 and 8, and A distribution map is created and displayed on the display 5. The user designates an RFID tag (article 30a) at a position where data acquisition is desired based on the display of the display 5. Then, the reader 1 communicates with a designated RFID tag and acquires data.

  That is, the mode setting switch is operated from the group of the key switches 4 to set the position designation mode, and the reader 1 is held in the state where the desired article 30a is present and the start switch is operated. Then, since a reading command in the position designation mode is sent from the device control unit 19 to the communication control unit 20, the communication control unit 20 first simplifies the intersection angle α between the antennas 7 and 8 (hereinafter referred to as the antenna angle). ), The initial value of the transmission output is set (step S1 in FIG. 8).

  Next, the communication control unit 20 drives and controls the motor 17 via the driver 25 so that the antenna angles of both the antennas 7 and 8 are set to the initial angles. Note that the predetermined setting angle at this time is a large angle at which communication with the RFID tag existing in the immediate vicinity of the reader 1 is possible. Then, the interrogation wave is transmitted from the transmission antenna 7 with the initially set output, and it waits for the reception antenna 8 to receive the response wave.

  When receiving the response wave, the communication control unit 20 sends the antenna angle at that time and the transmission output of the interrogation wave (carrier wave) to the device control unit 19 (the reading process in step S2 above). The device control unit 19 stores the transmitted antenna angle and transmission output value in, for example, its own RAM (storage means) 23. Note that the reading process ends when a predetermined short time elapses from the transmission of the interrogation wave, regardless of whether or not the response wave is received.

  When the reading process is completed, the communication control unit 20 increases the transmission output by one step, increases the antenna angle by one step (steps S3 to S6), and performs reading again (step S2). Thereafter, when the transmission output is increased one step at a time, and the operation of executing the reading procedure by decreasing the antenna angle one step at a time is repeated a plurality of times, the communication control unit 20 ends the reading operation for creating the distribution map and ends. A notification is transmitted to the device control unit 19.

  Upon receipt of the distribution map creation reading operation end notification, the device control unit 19 calculates the position of the RFID tag 29 that transmitted the response wave from the antenna angle when the response wave was received (step S7), and the calculated position Is displayed on the display 5 as shown in FIG. 2 (step S8). The position of the RFID tag 29 at this time is, for example, the center point of the directivity intersection range of both antennas 7 and 8. This completes the creation and display of the distribution map of the RFID tag 29 (article 30). In this map, the position of each RFID tag 29 is displayed in relation to the area where the directivity intersection range of both antennas 7 and 8 changes.

  The user designates the RFID tag 29a of the article 30a at a desired position from the distribution map of the RFID tag 29 displayed on the display 5 (step S9). This designation is performed by touching the RFID tag 29a to be read out of the RFID tags 29 displayed on the display device 5 with a touch pen or the like. Then, the device control unit 20 acquires the antenna angle and the transmission output value from the RAM 23 when the response wave of the RFID tag 29a is received from the designated position, and gives the antenna angle and the transmission output value to the communication control unit 20. (Step S10).

  The communication control unit 20 drives the motor 17 so that the antenna angles of both the antennas 7 and 8 become the intersection angle given from the device control unit 19. Then, the communication control unit 20 stops the motor 17 when the intersection angle between the two antennas 7 and 8 reaches the antenna angle given from the device control unit 19 (step S11), and the output given from the device control unit 19 The interrogation wave is transmitted from the transmitting antenna 7 (step S12). At this time, the crossing range and the transmission output of the directivity between the transmitting antenna 7 and the receiving antenna 8 are the same as the crossing range and the transmission output at the time of the previous map creation, and therefore the reader 1 can use the RFID tag 29a of the article 30a. To acquire data (step S13).

  When it is desired to acquire data from the RFID tag of another article based on the tag distribution map, the switch is repeatedly operated from the group of key switches 4. Then, the device control unit 19 displays the tag distribution map created as described above on the display 5 (step A1 in FIG. 9). In the tag distribution map, the user touches the RFID tag to be read with a touch pen or the like (step A2). Then, in the same manner as described above, both antennas 7 and 8 are controlled to the antenna angle corresponding to the designated RFID tag, and the interrogation wave is transmitted from the transmission antenna 7 with the transmission output corresponding to the designated RFID tag. The response wave is received from the RFID tag (step A3 to step A6).

  Next, an operation in the case of searching for an article to which an RFID tag 29b having a specific ID number is attached from among the scattered articles 30 as shown in FIG. 3 will be described with reference to the flowcharts of FIGS. . In this case, generally, first, the reader 1 creates a distribution map of RFID tags in the same manner as described above. Next, when the user inputs the ID number of the RFID tag that the user wants to search, the reader 1 communicates with the RFID tag 29 of the article 30 again, and if there is an RFID tag having the ID number to be searched, the distribution map The RFID tag having the ID number is displayed on the screen in a special display form.

    That is, the mode setting switch of the key switch 4 group is operated to set the search mode, and the start switch is operated while the reader 1 is held in a state facing the group of articles 30 scattered. Then, since a reading command in the search mode is sent from the device control unit 19 to the communication control unit 20, the communication control unit 20 first creates a tag distribution map in the same manner as described above and displays it on the display 5. (Step B1 to Step B8 in FIG. 10).

  When the tag distribution map is displayed on the display 5, the communication control unit 20 next sets the initial values of the antenna angle and the transmission output (step B9). In addition, the device control unit 19 displays on the display 5 to prompt the user to input the ID number of the RFID tag to be searched, and when the user inputs the ID number accordingly (step B10), the device control unit 19 displays the ID number. This is given to the communication control unit 20. Thereby, the communication control unit 20 performs the reading process by setting the antenna angle and the transmission output to the initial values in the same manner as described above (step B11).

  After performing the reading process, the communication control unit 20 determines whether or not the RFID tag with the designated ID number has been read (step B12). If there is no RFID tag that can be communicated, or even if communication is possible and the RFID tag of the specified ID number is not found, the communication control unit 20 increases the transmission output by one step and changes the antenna angle by one step for transmission. Processing is performed (“NO” in step B12, “NO” in step B13, “NO” in step B14 and step B15, “NO” in step B16, step B11, and step B12).

  When communication is possible with the RFID tag 29b having the ID number that matches the specified ID number ("YES" in step B12), the communication control unit 20 determines the antenna angle and transmission output value at that time as the device control unit 19 Send to. The device control unit 19 calculates the position of the RFID tag 29b from the antenna angle and the transmission output value sent from the communication control unit 20 (step B17), and displays the distribution map obtained previously on the display 5. Of the RFID tags displayed on the distribution map, the position of the designated RFID tag is blinked and displayed (step B18). Since the user can know the position of the RFID tag 29b to be searched by looking at the display 5, the user can search for the target article 30b from the display.

  Even if the antenna angle and the transmission output are changed one step at a time, if communication with the RFID tag of the designated ID number is not possible ("NO" in step B15), the communication control unit 20 notifies the device control unit 19 to send. And the apparatus control part 19 displays that the RFID tag designated on the indicator 5 does not exist (step B19). Accordingly, the user can search for and obtain the article 30b itself together with information on the target article 30b by looking at the display.

  As described above, according to the present embodiment, when it is desired to obtain information from the RFID tag of a specific article among many articles attached with the RFID tag, the distribution map of the article is displayed on the display 5 and the desired map is obtained from the map. When the article is designated, the reader 1 communicates with the RFID tag of the designated article to acquire information, so that it is possible to prevent the occurrence of an unexpected trouble such as reading information on the RFID tag.

In this case, each of the transmitting antenna 7 and the receiving antenna 8 may be one, and the interrogation wave may be one frequency, so that it can be configured at low cost.
<Second Embodiment>
FIGS. 12 to 14 show a second embodiment of the present invention. The difference from the first embodiment is that the transmission antenna 7 and the reception antenna 8 are constituted by Yagi antennas. As shown in FIG. 14, the Yagi antenna is configured by disposing a plurality of waveguide elements 32 on the front side of the feeding element 31 and a reflecting element 33 on the rear side. The length L1 of 31 is ½ wavelength of the interrogation wave, the length L2 of the waveguide element 32 is ½ wavelength−α of the interrogation wave, and the length L3 of the reflection element 33 is ½ wavelength + α of the interrogation wave. It has been established. The feeding element 31 preferably has a 1/32 wavelength at a minimum.

  Such a Yagi antenna can be made smaller than a patch antenna. Further, since the directivity is higher than that of the patch antenna, that is, the communication area is narrowed, the crossing range of directivity between the transmitting antenna 7 and the receiving antenna 8 is narrower than that in the case where the patch antenna is configured. This is advantageous when communicating with two RFID tags (improved selectivity).

<Third Embodiment>
15 and 16 show a third embodiment of the present invention. This embodiment differs from the first embodiment in that a patch antenna is used for the transmission antenna 7 and a Yagi antenna is used for the reception antenna 8.

<Fourth Embodiment>
17 and 18 show a fourth embodiment of the present invention. This embodiment is different from the first embodiment in that a Yagi antenna is used for the transmission antenna 7 and a patch antenna is used for the reception antenna 8.

<Fifth Embodiment>
19 and 20 show a fifth embodiment of the present invention. In this embodiment, at least one of the transmission antenna 7 and the reception antenna 8 is configured by a Yagi antenna, and this Yagi antenna is provided in the reader 1 so as to be rotatable. In this configuration, if the Yagi antennas are different from each other by 90 degrees as shown in FIGS. 19 and 20, the polarization planes of the Yagi antenna can be different from each other by 90 degrees.

  In the example of FIG. 19 in which the polarization plane is vertical, communication is possible with an RFID tag having a vertical transmission / reception antenna, but communication with an RFID tag with a horizontal transmission / reception antenna is not possible. Conversely, in the example of FIG. 20 in which the plane of polarization is horizontal, communication is possible with an RFID tag whose transmission / reception antenna is horizontal, but communication with an RFID tag whose transmission / reception antenna is vertical is impossible.

For this reason, when the state of the RFID tag for which information is to be obtained is known in advance, the antenna can be more reliably communicated with the RFID tag for which information is to be acquired by matching the plane of polarization with the RFID tag tag by rotating the antenna. .
Further, by rotating the Yagi antenna, communication with all RFID tags is possible regardless of the orientation of the RFID tag.
<Sixth Embodiment>
21 and 22 show a sixth embodiment of the present invention. This embodiment differs from the first embodiment described above in that the angle of one antenna can be changed while the angle of the other antenna is kept constant.
That is, the transmitting antenna 7 and the receiving antenna 8 are configured such that the angles can be independently changed by a dedicated crossing angle adjusting mechanism. When the angle of the receiving antenna 8 is changed within the movable range while the transmitting antenna 7 is kept at the initial setting angle, the range where the directivities of both the antennas 7 and 8 intersect is shown in FIG. The range is shaded. Next, when the transmitting antenna 7 is changed by one step angle, and the receiving antenna 8 is changed within the movable range while the transmitting antenna 7 is kept at the angle, the directivity of both antennas 7 and 8 is changed. The range where the sexes intersect is the range where the diagonal line is added to FIG.

  In this way, by sequentially changing the angle of the transmitting antenna 7 step by step, and changing the angle of the receiving antenna 8 within the movable range while keeping the transmitting antenna 7 at the changed angle, as a result, The region where the directivity overlaps extends over a wide range in the left-right direction. Therefore, the RFID tag distribution map can be displayed over a wide range as shown in FIG.

<Other embodiments>
The present invention is not limited to the embodiment described above and shown in the drawings, and can be expanded or changed as follows.
The reader 1 is not limited to a read-only one, and may be a writable one.
In the fifth embodiment, the Yagi antenna is selected as the antenna that changes the plane of polarization. However, a patch antenna may be used.
The transmission antenna 7 and the reception antenna 8 are not limited to a patch antenna or a Yagi antenna.
The transmission antenna 7 and the reception antenna 8 may be accommodated in the main body 3.
The information is not limited to read only for reading information from the RFID tag, and information that can also be written to the RFID tag may be used.

The 1st Embodiment of this invention is a figure which shows the overlapping range of the directivity of a transmitting antenna and a receiving antenna Plan view of the head of the reader showing the distribution map of the RFID tag The perspective view which shows the state of the dot of the articles | goods which attached | subjected the RFID tag Perspective view of the reader Perspective view of patch antenna A plan view showing a mechanism for changing the crossing angle between the transmitting antenna and the receiving antenna Block diagram showing the electrical configuration of the reader Flow chart for creating a distribution map and communicating with an RFID tag selected from the distribution map Flowchart for communicating with an RFID tag selected from a created distribution map Flow chart for creating a distribution map Flowchart for communicating with an RFID tag having a specified ID number FIG. 1 equivalent diagram showing a second embodiment of the present invention Perspective view of the reader Plan view showing the configuration of the Yagi antenna FIG. 13 equivalent diagram showing the third embodiment of the present invention 1 equivalent diagram FIG. 13 equivalent view showing the fourth embodiment of the present invention 1 equivalent diagram FIG. 13 shows the fifth embodiment of the present invention and shows the polarization plane in a vertical state. FIG. 13 equivalent diagram showing the polarization plane in a horizontal state The top view which shows the state which shows the 6th Embodiment of this invention, and the crossing range of the directivity of a transmitting antenna and a receiving antenna changes 2 equivalent diagram

Explanation of symbols

  In the drawings, 1 is a portable RFID tag reader, 7 is a transmitting antenna, 8 is a receiving antenna, 12 is a shaft, 13 is a swing link, 16 is a rack, 17 is a motor, 18 is a pinion, 19 is a device control unit, 20 is a communication control unit, 29 is an RFID tag, and 30 is an article.

Claims (7)

The main body is provided with a transmission antenna that transmits an interrogation wave and a reception antenna that receives a response wave returned from the RFID tag that has received the interrogation wave, and the RFID tag communicates with the transmission antenna and the reception antenna. In a portable RFID tag reader that reads information recorded on an RFID tag,
The transmitting antenna and the receiving antenna have directivity in a direction in front of an operator holding the main body,
At least one of the transmitting antenna and the receiving antenna is movably provided in the main body so that the directivity of the other antenna intersects the other antenna and the range of the directivity intersecting changes. A portable RFID tag reader characterized by the above.   An area in which the display unit is provided, and when the directivity range where the transmitting antenna and the receiving antenna intersect is changed, the RFID tag communicated with the display is changed to the crossed directivity range. The portable RFID tag reader according to claim 1, wherein the portable RFID tag reader is displayed.   3. The portable RFID tag reader according to claim 1, wherein the intensity of the radio wave transmitted from the transmission antenna is changeable.   4. The portable RFID tag reader according to claim 1, wherein at least one of the transmission antenna and the reception antenna is configured to be able to change a polarization plane.   At least one of the transmitting antenna and the receiving antenna is configured by a patch antenna, and the length and width of the antenna surface are set to a size of 1/2 to 1/32 of the wavelength of the transmitted / received radio wave. The portable RFID tag reader according to any one of claims 1 to 4.   At least one of the transmitting antenna and the receiving antenna is composed of a Yagi antenna, and the length of the antenna element is set to a size of 1/2 to 1/32 of the wavelength of the transmitted / received radio wave. The portable RFID tag reader according to any one of claims 1 to 4, wherein the portable RFID tag reader is provided.   The transmission antenna is configured by a patch antenna, the reception antenna is configured by a Yagi antenna, or the transmission antenna is configured by a Yagi antenna, and the reception antenna is configured by a patch antenna. 5. The portable RFID tag reader according to any one of 4 to 4.

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