JP6205379B2 - antenna - Google Patents

Description

  Embodiments described herein relate generally to an antenna used in, for example, an RFID (Radio Frequency Identification) tag communication device.

  Recently, with the widespread use of RFID tags, handy type RFID tag communication devices that can be easily handled in various environments are known. Such an RFID tag communication device is required to reduce the weight and size of the device in order to reduce the burden on the operator. Along with the demand for reduction in size and weight of such an RFID tag communication device, the demand for reduction in weight and size of the antenna is also increasing.

JP 2013-70341 A

  For this reason, for example, if an antenna component such as a radiator is made thin in order to reduce the size and weight of the antenna, an error is likely to occur in the mounting position of the component, and variations in antenna characteristics are likely to occur.

  Accordingly, the problem to be solved by the present invention is to provide an antenna that can easily adjust antenna characteristics and improve the yield of products.

An antenna according to an embodiment includes a ground metal plate, a radiator, a power feeding member, a cover, and first adjusting means. The radiator has an annular shape having notches at positions facing each other on the outer periphery, and radiates radio waves to space. The feeding member is provided between the ground metal plate and the radiator, has a strip shape extending from the outside of the radiator toward the center, and excites the radiator by a high-frequency signal fed from the feeding point. The cover is disposed on a side of the radiator that is separated from the ground sheet metal, and covers the ground sheet metal, the radiator, and the power supply member. The first adjusting means includes a first screw that is screwed in from the side of the ground sheet metal that is away from the cover and presses the power feeding member toward the radiator, and adjusts the distance between the radiator and the power feeding member. The first screw is screwed in from the side away from the cover of the ground metal plate at a position where the radiator and the power supply member intersect, and presses the power supply member toward the radiator.

FIG. 1 is a perspective view of an RFID tag communication apparatus including a patch antenna according to an embodiment. FIG. 2 is a perspective view showing a state in which the back cover of the patch antenna of FIG. 1 is removed. FIG. 3 is a perspective view showing a state in which the front and back covers of the patch antenna of FIG. 1 are removed. FIG. 4 is a view of the structure of FIG. 2 as viewed from the direction of arrow F4. FIG. 5 is a cross-sectional view showing a state where the patch antenna of FIG. 4 is cut by F5-F5. FIG. 6 is a diagram for explaining a method of adjusting the antenna characteristics of the patch antenna of FIG. FIG. 7 is a diagram showing the relationship between the VSWR and the frequency of the patch antenna of FIG. FIG. 8 is a flowchart for explaining a method of adjusting the VSWR value of the patch antenna shown in FIG.

  Hereinafter, embodiments of an antenna according to the present invention will be described with reference to the drawings. In the present embodiment, a patch antenna provided in the RFID tag communication apparatus is illustrated and described in detail.

  First, the RFID tag communication device 1 will be described. FIG. 1 is an overall perspective view of the RFID tag communication apparatus 1.

  The RFID tag communication device 1 wirelessly communicates with an RFID (Radio Frequency Identification) tag attached to each product, for example, when inventorying a product placed in a store or a warehouse, and EPC (Electronic Product) of the RFID tag Code) is a device that reads data.

  The RFID tag communication device 1 includes a handle 2, a patch antenna 100, a clip 3, and a terminal S.

  The handle 2 is a substantially cylindrical rod-shaped member. The rod-shaped member is bent at one place to form the shoulder portion 21. A patch antenna 100 is attached to the front end of the handle 2 so as to be rotatable by a predetermined angle. The patch antenna 100 is a plate-like member having a substantially square predetermined thickness. Specifically, the patch antenna 100 includes a front cover 110, a back cover 120, and an antenna unit 200 described later. The front cover 110 and the back cover 120 are disposed so as to cover both surfaces of the antenna unit 200 and protect the antenna unit 200 from the external environment.

  The clip 3 is attached to the shoulder portion 21 of the handle 2. The clip 3 has two claws 31 that are spaced apart along the longitudinal direction of the handle 2. The two claws 31 are provided so as to be separated from each other.

  As the terminal S, a tablet terminal or a smartphone equipped with a display for displaying data received from an RFID tag attached to a product can be used. The terminal S is sandwiched and fixed between the two claws 31 of the clip 3.

  Next, the internal structure of the patch antenna 100 will be described with reference to FIGS. FIG. 2 shows a state where the back cover 120 of the patch antenna 100 of the RFID tag communication apparatus 1 of FIG. 1 is removed. In FIG. 2, the outline of the ground metal plate 300 described later is indicated by a broken line in order to make the internal structure of the patch antenna 100 easier to see. FIG. 3 is a perspective view showing the structure of the antenna unit 200 viewed from the front cover 110 side. FIG. 4 is a view of the structure of FIG. 2 as viewed from the direction of arrow F4. In addition, as in FIG. 2, the ground sheet metal 300 has an outline indicated by a broken line in order to make the internal structure easy to see. FIG. 5 is a diagram in which the antenna unit 200 and the front cover 110 are cut at the locations indicated by F5-F5 in FIG.

  As shown in FIGS. 2 and 3, the antenna unit 200 includes a ground sheet metal 300, a radiator 400, a power feeding member 500, and an adjustment mechanism 600 (first screw 610 and second screw 620).

  The ground metal plate 300 is a box-shaped member having one surface formed by bending a metal plate. Specifically, the ground metal plate 300 includes a substantially rectangular plate-like bottom wall 320 to which a radiator 400 and the like to be described later are fixed, and a side wall 310 formed around the bottom wall 320 by bending. Inside the side wall 310 of the ground metal plate 300, the radiator 400 and the power supply member 500 are disposed. Then, the ground metal plate 300 is attached to the front cover 110 so as to close the opening 330 formed by an edge spaced from the bottom wall 320 of the side wall 310.

  The radiator 400 is a substantially annular thin plate as shown in FIGS. Radiator 400 includes two notches 410 at positions on the outer periphery thereof that face each other. In addition, the radiator 400 can output circularly polarized waves by having the two notches 410. A surface on the front cover 110 side of the radiator 400 is a first surface 420, and a back surface thereof is a second surface 440. Radiator 400 is disposed substantially parallel to bottom wall 320 of ground sheet metal 300. Radiator 400 is fixed to bottom wall 320 of ground sheet metal 300 via a plurality of spacers 430 so that the center of radiator 400 overlaps the approximate center of ground sheet metal 300. In the present embodiment, the radiator 400 is fixed to the bottom wall 320 via spacers 430 arranged at three locations. The spacer 430 is made of resin that does not affect the antenna performance of the radiator 400.

  The power supply member 500 has a strip-like thin plate shape. As shown in FIG. 5, the power feeding member 500 is disposed between the bottom wall 320 of the ground metal plate 300 and the radiator 400. The surface on the radiator 400 side of the power supply member 500 is a first surface 530 and the back side surface is a second surface 540. The power feeding member 500 extends from the outside of the outer periphery of the radiator 400 toward the center, and is disposed at a position where the radiator 400 and a part of the power feeding member 500 overlap each other. That is, the power feeding member 500 is extended from one corner of the ground metal plate 300 toward the opposite corner of the bottom wall 320 inside the ground metal plate 300. Then, both end portions in the longitudinal direction of the power supply member 500 are fixed to the bottom wall 320 of the ground metal plate 300 with screws through spacers 510, respectively. In addition, the power feeding member 500 has a power feeding point 520 outside the outer periphery of the radiator 400 on the second surface 540. The feeding point 520 is connected to a feeding circuit (not shown) of the RFID tag communication apparatus 1 via a cable (not shown), and supplies power to the feeding member 500. The power supply member 500 excites the radiator 400 by the high frequency signal supplied from the power supply point 520.

  The adjusting mechanism 600 includes a first screw 610 (first adjusting means) and a second screw 620 (second adjusting means). Corresponding to the first screw 610, the ground metal plate 300 is provided with a nut 630 for attaching the first screw 610 to the bottom wall 320 of the ground metal plate 300. Corresponding to the second screw 620, the ground metal plate 300 is provided with a nut 650 for attaching the second screw 620 to the bottom wall 320. As shown in FIGS. 4 and 5, the first screw 610 is disposed at a position where the radiator 400 and the feeding member 500 intersect. The first screw 610 is screwed through the ground sheet metal 300 from the outside of the bottom wall 320. The first screw 610 is screwed from the bottom wall 320, and the tip of the first screw 610 pushes the power feeding member 500 toward the radiator 400. That is, the length of the first screw 610 is designed to be a length that can bend the power supply member 500 by a predetermined amount. The first screw 610 is made of, for example, a resin material and does not affect the antenna performance.

  The second screw 620 is disposed at a position that does not overlap the power supply member 500 inside the radiator 400. The second screw 620 is screwed through the ground sheet metal 300 from the outside of the bottom wall 320. The second screw 620 is screwed from the bottom wall 320, and the tip of the second screw 620 pushes the front cover 110 away from the radiator 400. That is, the length of the second screw 620 is designed to be a length that can bend the front cover 110 by a predetermined amount. The second screw 620 is made of, for example, a resin material and does not affect the antenna performance.

  In the present embodiment, the first screw 610 and the second screw 620 are attached to the bottom wall 320 of the ground metal plate 300 using the nuts 630 and 650, but the attachment structure is not limited to this. For example, the bottom wall 320 can be fixed by providing a screw hole. In the present embodiment, as the first screw 610 and the second screw 620, set screws having no large head are used. By using the set screw, it is possible to prevent the heads of the first screw 610 and the second screw 620 from projecting greatly toward the back cover 120 side of the bottom wall 320, and a gap between the back cover 120 and the ground sheet metal 300 is formed. Can be thinned.

  FIG. 6 is a cross-sectional view of the antenna unit 200 and the front cover 110 taken along F6-F6 shown in FIG.

Hereinafter, the adjusting mechanism 600 will be further described with reference to FIG.
The first screw 610 is screwed into the nut 630 from the back cover 120 side of the bottom wall 320 of the ground metal plate 300, and the tip of the first screw 610 contacts the second surface 540 of the power supply member 500. When the first screw 610 is further screwed from the state where the tip of the first screw 610 is in contact with the power supply member 500, the tip of the first screw 610 presses the power supply member 500 toward the radiator 400. A state in which the first screw 610 presses the power feeding member 500 toward the radiator 400 and is bent is indicated by a broken line.

  In the present embodiment, when the power supply member 500 is bent in the direction away from the bottom wall 320 by the pressing force of the first screw 610, that is, in the direction approaching the radiator 400, the antenna characteristics of the patch antenna 100 change. Specifically, the frequency at which the VSWR (voltage standing wave ratio) of the patch antenna 100 is minimized increases as the distance between the power feeding member 500 and the radiator 400 becomes closer.

  The arrangement position of the first screw 610 is not particularly limited, but it is preferable to arrange the first screw 610 at a position where the apex of bending of the power supply member 500 is closest to the radiator 400, that is, at a point where both members intersect.

  On the other hand, the second screw 620 is screwed into the nut 650 from the back cover 120 side of the bottom wall 320 of the ground metal plate 300, and the tip of the second screw 620 contacts the back surface 111 of the front cover 110. When the second screw 620 is further screwed in from the state in which the tip of the second screw 620 is in contact, the tip of the second screw 620 presses the front cover 110 away from the radiator 400. A state in which the second screw 620 presses and deflects the front cover 110 in a direction away from the radiator 400 is indicated by a broken line.

  In the present embodiment, when the front cover 110 is bent in the direction away from the bottom wall 320 by the pressing force of the second screw 620, that is, in the direction away from the radiator 400, the antenna characteristics of the patch antenna 100 change. Specifically, the frequency at which the VSWR of the patch antenna 100 is minimized decreases as the distance between the front cover 110 and the radiator 400 increases.

  The arrangement position of the second screw 620 is not particularly limited, but it is preferable to arrange the second screw 620 at a position in the vicinity of the center of the front cover 110 that does not contact the power supply member 500.

  Next, the procedure for adjusting the antenna characteristics of the assembled patch antenna 100 will be described with reference to the flowchart shown in FIG. In the following, the assembled patch antenna 100 refers to a state in which the antenna unit 200 and the front cover 110 are assembled as shown in FIG. In other words, the assembled patch antenna 100 is the patch antenna 100 before the back cover 120 is attached.

  First, the operator attaches the assembled patch antenna 100 to a measurement device (for example, a network analyzer) and measures the VSWR (Act 1). The measurement result is displayed on a monitor (not shown). An example of the measurement result is shown in FIG. In FIG. 7, the vertical axis represents VSWR (1 is the minimum value), and the horizontal axis represents the frequency of the high-frequency signal that feeds the antenna. The VSWR of the patch antenna shows a minimum peak at a specific feeding frequency. In other words, the frequency indicating the peak of VSWR is slightly different for each patch antenna 100 after assembly. A region X shown at the center of the horizontal axis indicates an allowable frequency range indicating the peak of VSWR. That is, if the peak frequency of the VSWR of the assembled patch antenna 100 is within the region X, it can be understood that the patch antenna 100 is an antenna having a performance substantially as designed.

  A solid line O in FIG. 7 shows an example of an antenna VSWR whose antenna characteristics are within an allowable range (region X). The dotted line P shows an example in the case where the peak frequency of the VSWR is out of the region X. An alternate long and two short dashes line Q shows an example in the case where the peak frequency of VSWR is out of the region X.

  After measuring the VSWR of the antenna in Act1, the operator determines whether or not the frequency indicating the peak of VSWR is lower than the region X (Act2), and the frequency indicating the peak of VSWR is higher than the region X It is determined whether the frequency (Act 3). An example when the frequency indicating the peak of VSWR is lower than the region X is indicated by a dotted line P in FIG. 7, and an example when the frequency indicating the peak of VSWR is higher than the region X is indicated by a two-dot chain line in FIG. Indicated by Q.

  When the frequency indicating the peak of VSWR measured in Act1 is lower than the region X (Yes in Act2), the operator screws the first screw 610 (Act4) and brings the feeding member 500 slightly closer to the radiator 400. Again, VSWR is measured (Act 5). When the operator screws the first screw screw 610, for example, the peak of VSWR moves in the direction indicated by the dotted arrow L in FIG. The operator repeats the procedures of Acts 4 and 5 until the VSWR peak measured at Act 5 falls within the region X (Yes at Act 6).

  On the other hand, when the frequency indicating the peak of VSWR measured in Act1 is higher than the region X (No in Act2, Yes in Act3), the operator screws the second screw 620 (Act7) to radiate the front cover 110. The VSWR is measured again (Act 8). When the operator screws in the second screw 620, for example, the peak of VSWR moves in the direction indicated by the two-dot chain line arrow R in FIG. The operator repeats the procedures of Acts 7 and 8 until the VSWR peak measured at Act 8 falls within the region X (Yes at Act 9).

  As described above, the patch antenna 100 according to the present embodiment includes the adjustment mechanism 600. For this reason, even when the VSWR peak of the patch antenna 100 is out of the region X, the VSWR peak of the patch antenna 100 is adjusted within the range of the region X, that is, an appropriate range using the adjustment mechanism 600. Can do.

  In addition, the adjustment mechanism 600 according to the present embodiment eliminates variations in impedance among products with a simple configuration in which only the first screw 610 or the second screw 620 is rotated according to the measurement result of VSWR. Therefore, the adjustment of the antenna characteristics of the patch antenna 100 can be simplified.

  In addition, the adjustment mechanism 600 shown in the present embodiment only needs to add the first screw 610 and the second screw 620 to the existing patch antenna, has a simple configuration, and can reduce the improvement cost.

  These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, in the present embodiment, the first screw 610 and the second screw 620 are both screwed from the ground metal plate 300 and are arranged substantially vertically toward the power supply member 500 and the front cover 110. However, the adjustment mechanism 600 of the present embodiment is not limited to this configuration.

  For example, the first screw 610 and the second screw 620 of the adjustment mechanism 600 may be configured to penetrate the back cover 120 and the ground metal plate 300. In other words, the first screw 610 and the second screw 620 are disposed so as to be exposed on the outer surface of the back cover 120, so that the antenna of the patch antenna can be seen from the outside of the back cover 120 even after the back cover 120 is assembled. It is possible to adjust the characteristics.

  In this embodiment, VSWR is used as an index for measuring antenna characteristics, but the index for measuring antenna characteristics is not limited to this. For example, it may be a reflectance or a voltage reflection coefficient (S parameter S11).

The patch antenna 100 of the RFID tag communication apparatus 1 shown in the present embodiment is an antenna that generates circularly polarized waves. For example, the antenna that generates vertically polarized waves without the notch 410 of the radiator 400 is used. The present invention can also be applied to.
Hereinafter, the invention described in the scope of claims at the beginning of the application of the present application will be added.
[1] Ground sheet metal,
A radiator that radiates radio waves into space;
A high-frequency signal provided between the ground sheet metal and the radiator and fed from a feeding point
A power feeding member for exciting the radiator by:
The radiator is disposed on a side away from the ground sheet metal, the ground sheet metal, the release plate.
And a cover that covers the power supply member,
First adjusting means for adjusting a distance between the radiator and the power supply member;
An antenna characterized by.
[2] The antenna according to [1], wherein the first adjusting means includes a first screw that is screwed from a side of the ground metal plate that is separated from the cover and presses the power feeding member toward the radiator. .
[3] The radiator has an annular shape having notches at positions facing each other on the outer periphery,
The power supply member has a strip shape extending from the outside of the radiator toward the center,
The first screw is screwed in from the side away from the cover of the ground metal plate at a position where the radiator and the power supply member intersect, and presses the power supply member toward the radiator. The antenna according to [2].
[4] The antenna according to any one of [1] to [3], further comprising second adjusting means for adjusting a distance between the cover and the radiator.
[5] The second adjusting means includes a second screw that is screwed in from the side of the ground metal plate that is away from the cover and presses the surface of the cover that faces the radiator in a direction away from the radiator. [4] The antenna according to [4].

DESCRIPTION OF SYMBOLS 1 ... RFID tag communication apparatus, 2 ... Handle, 3 ... Clip, 21 ... Shoulder part, 31 ... Claw, 100 ... Patch antenna, 110 ... Front cover, 111 ... Back surface, 120 ... Back cover, 200 ... Antenna part, 300 ... Ground sheet metal, 310 ... side wall, 320 ... bottom wall, 330 ... opening, 400 ... radiator, 410 ... notch, 420 ... first surface, 430 ... spacer, second surface ... 440, 500 ... feeding member, 510 ... spacer, 520 ... feed point, 530 ... first surface, 540 ... second surface, 600 ... adjustment mechanism, 610 ... first screw, 620 ... second screw, 630 ... nut, 650 ... nut

Claims (3)

With ground sheet metal,
A radiator that radiates radio waves into space;
A power supply member that is provided between the ground metal plate and the radiator, and excites the radiator by a high-frequency signal fed from a power supply point;
A cover that is disposed on a side of the radiator that is separated from the ground metal plate, and covers the ground metal plate, the radiator, and the power supply member;
First adjusting means for adjusting a distance between the radiator and the feeding member ;
The first adjusting means includes a first screw that is screwed in from the side of the ground metal plate that is separated from the cover and presses the power feeding member toward the radiator,
The radiator has an annular shape having notches at positions facing each other on the outer periphery,
The power supply member has a strip shape extending from the outside of the radiator toward the center,
The first screw is screwed from the side of the ground sheet metal away from the cover at a position where the radiator and the power feeding member intersect, and presses the power feeding member toward the radiator. Antenna. The antenna according to claim 1 , further comprising second adjusting means for adjusting a distance between the cover and the radiator. The second adjusting means includes a second screw that is screwed from a side of the ground metal plate that is separated from the cover and presses a surface of the cover that faces the radiator in a direction away from the radiator. The antenna according to claim 2 .