JP3645239B2 - Dipole antenna, tag and moving object identification system using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dipole antenna for wireless communication, a tag using the dipole antenna, and a mobile object identification system.
[0002]
[Prior art]
As a dipole antenna, for example, there is a small antenna in which a pair of antenna elements is formed as a pattern on a dielectric substrate. This small dipole antenna is built in a tag or a portable electronic device used for detecting an article or the like.
[0003]
In such a dipole antenna, in order to adjust its impedance, the dielectric constant and thickness of the dielectric substrate are changed, the width and length of the pattern of the dipole antenna are changed, or they are completely electrically insulated. Another pattern was placed in parallel with the dipole antenna.
[0004]
Patent Document 1 discloses a technique for adjusting impedance by bending the tip of an antenna element.
[0005]
Furthermore, Patent Document 2 discloses a technique of adjusting impedance by providing a stub between a dipole antenna and a connection line.
[0006]
[Patent Document 1]
Japanese Patent Publication No. 4-12043 [Patent Document 2]
Japanese Examined Patent Publication No. 3-71807 [0007]
[Problems to be solved by the invention]
However, in any of the above conventional methods, it is difficult to adjust the impedance of the dipole antenna at any time, which is not an easy adjustment method, and fine adjustment of the impedance is difficult.
[0008]
Further, in the method of arranging another pattern in parallel with the dipole antenna and the methods of Patent Literature 1 and Patent Literature 2, there is a possibility that the antenna directivity changes as the impedance is adjusted. It was extremely difficult to adjust the impedance while maintaining the above.
[0009]
Accordingly, the present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a dipole antenna capable of easily adjusting impedance while maintaining the antenna directivity. .
[0010]
Another object of the present invention is to provide a tag and a moving body identification system using such a dipole antenna of the present invention.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a dipole antenna in which a pair of antenna elements is formed as a pattern on a dielectric, and at least one of the antenna elements is located farther from the feed point than the intermediate point of the antenna elements. The impedance adjustment pattern having a width narrower than that of the antenna element is arranged along the line from the connection position to the edge of the antenna element.
[0012]
According to the dipole antenna of the present invention having such a configuration, the impedance of the dipole antenna can be adjusted by cutting the impedance adjustment pattern halfway and changing the length thereof. Since the impedance adjustment pattern is a line having a narrower width than the antenna element, it can be easily cut, and even if its length is changed, it hardly affects the directivity characteristics of the antenna. .
[0014]
Further, the further away from the feeding point , the higher the potential of the antenna element. For this reason, as the connection position of the impedance adjustment pattern is further away from the feeding point, the impedance change with respect to the change in the length of the impedance adjustment pattern becomes clearer, and the impedance adjustment becomes easier.
[0016]
Furthermore, if the connection position of the impedance adjustment pattern is closer to the tip than the middle point of the antenna element that is separated from the feeding point, the impedance adjustment is extremely easy.
[0019]
In the present invention, the impedance adjustment pattern is disposed along the antenna element on the dielectric .
[0020]
By arranging the impedance adjustment pattern in this way, the area occupied by the impedance adjustment pattern can be reduced, and the increase in size of the dipole antenna can be suppressed.
[0021]
In the present invention, since the cut adjustment mark is provided in the vicinity of the impedance adjustment pattern, the length of the impedance adjustment pattern can be easily adjusted.
[0022]
On the other hand, in the tag of the present invention, a semiconductor chip that communicates data through the dipole antenna is connected to the feeding point of the dipole antenna of the present invention.
[0023]
According to the tag of the present invention having such a configuration, a semiconductor chip is connected to the feeding point of the dipole antenna of the present invention. Since the impedance of the dipole antenna can be easily adjusted as described above, impedance matching between the dipole antenna and the semiconductor chip can be easily realized, and the tag transmission / reception performance can be maintained high.
[0024]
Moreover, the mobile body identification system of this invention is provided with the tag of this invention, and the reading / writing terminal device which transmits / receives data between this tag.
[0025]
According to the mobile object identification system of the present invention having such a configuration, since the tag of the present invention is used, the tag transmission / reception performance is excellent, and the performance as the system is excellent.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0027]
FIG. 1 is a plan view showing an embodiment of the dipole antenna of the present invention. FIG. 2 is a side view showing the dipole antenna.
[0028]
In the dipole antenna 11 of this embodiment, for example, a metal film covering the entire surface of the dielectric substrate 12 is patterned by etching or the like to form a pair of antenna elements 13 and 14 and an impedance adjustment pattern 15 on the dielectric substrate 12. It is a thing.
[0029]
The dielectric substrate 12 has a thickness T having a relative dielectric constant Er. The entire back surface of the dielectric substrate 12 is covered with a metal film 16.
[0030]
Each antenna element 13, 14 has a length L and a width W, respectively. The impedance adjustment pattern 15 is a line having a narrower width than the antenna element 14, is connected to the tip end angle of the antenna element 14, is bent in the middle thereof, and is arranged in parallel with the antenna element 14.
[0031]
Further, in this dipole antenna 11, an IC chip 17 is added, and this IC chip 17 is mounted and connected to a feeding point between the antenna elements 13 and 14. The IC chip 17 performs data communication through the dipole antenna 11. The dipole antenna 11 and the IC chip 17 are accommodated in a package (not shown) to constitute, for example, a tag. This tag is used in a mobile unit identification system described later.
[0032]
In order to maximize the input / output power of the IC chip 17, it is necessary to achieve impedance matching between the dipole antenna 11 and the IC chip 17. That is, if the conjugate impedance with respect to the intrinsic impedance Zc (= Rc−jXc (Ω)) of the IC chip 17 is Zc * (= Rc + jXc (Ω)) and the input impedance of the dipole antenna 11 is Z (= R + jX (Ω)). It is necessary to make the input impedance Z of the dipole antenna 11 coincide with the conjugate impedance Zc *. For this reason, the input impedance Z of the dipole antenna 11 is adjusted.
[0033]
Adjustment of the input impedance Z of the dipole antenna 11 is performed by cutting the impedance adjustment pattern 15 in the middle thereof and changing the length of the connection portion of the impedance adjustment pattern 15 to the antenna element 14.
[0034]
FIG. 3 is a graph showing the relationship between the input impedance Z of the dipole antenna 11 and the length t of the impedance adjustment pattern 15. In this graph, the resistance component R (Ω) of the input impedance Z is shown on the X axis, the reactance component X (Ω) of the input impedance Z is shown on the Y axis, and the change in the length t of the impedance adjustment pattern 15 is changed. The change of the resistance component R (Ω) and the reactance component X (Ω) associated with is shown.
[0035]
As the length t of the impedance adjustment pattern 15 is gradually increased from 0 as shown in the graph of FIG. 3, the resistance component R (Ω) and the reactance component X (Ω) gradually increase. The resistance component R (Ω) starts to decrease after reaching the maximum value as the length t of the impedance adjustment pattern 15 increases. Similarly, the reactance component X (Ω) also starts to decrease after reaching the maximum value. However, on this graph, the increase of the resistance component R (Ω) and the reactance component X (Ω) in the A1 direction cannot be completely represented, and therefore the resistance component R (Ω) and the reactance component X turned to decrease from the A2 direction. (Ω) is shown continuously. Further, the resistance component R (Ω) and the reactance component X (Ω) return to near their respective values when the length t = 0 with the extension of the length t of the impedance adjustment pattern 15, It gradually increases through the inside of the trajectory.
[0036]
As apparent from this graph, the input impedance Z of the dipole antenna 11 can be adjusted by changing the length t of the impedance adjustment pattern 15.
[0037]
Therefore, the impedance adjustment pattern 15 is cut in the middle to shorten the length t little by little, thereby changing the input impedance Z little by little to match the conjugate impedance Zc *, and the dipole antenna 11 and the IC chip 17. Match impedance between.
[0038]
FIG. 4 is a plan view illustrating a state where the impedance adjustment pattern 15 is cut in the middle thereof. The impedance adjustment pattern 15 is cut at the position P and is changed from the original length t1 to the length t2. At the original length t1, the input impedance Z is large and the sensitivity of the dipole antenna 11 is low. At the changed length t2, the input impedance Z becomes small and the sensitivity of the dipole antenna 11 becomes high.
[0039]
Thus, in this embodiment, the impedance adjustment pattern 15 is cut, the length thereof is changed, and the impedance between the dipole antenna 11 and the IC chip 17 is matched. Here, since the impedance adjustment pattern 15 is a line having a narrow width, the cutting can be easily performed, and the input impedance Z can be easily adjusted. In addition, since the impedance adjustment pattern 15 is arranged along the upper edge of the antenna element 14, it is not necessary to enlarge the dielectric substrate 12 and the dipole antenna 11 is not increased in size.
[0040]
Further, since the impedance adjustment pattern 15 is a line having a narrow width, even if the length t is changed, the directivity characteristic of the dipole antenna 11 hardly changes.
[0041]
FIG. 5 is a graph showing the directivity characteristics of the dipole antenna 11. Since the impedance adjustment pattern 15 is sufficiently narrower than the antenna element 14, the directivity of this graph does not change even if the length of the impedance adjustment pattern 15 is changed.
[0042]
Further, as shown in FIG. 4, the dipole antenna 11 may be provided with a scale-shaped cutting adjustment mark Q in advance. By providing such cutting adjustment marks Q in advance, it is possible to easily adjust the lengths of the impedance adjustment patterns of a plurality of dipole antennas uniformly. Alternatively, if a cutting adjustment mark is provided in advance at a position R where the sensitivity of the dipole antenna 11 is approximately “0”, the sensitivity of the dipole antenna 11 is approximately “0” by cutting the impedance adjustment pattern 15 at the position R. Can be easily adjusted.
[0043]
Even if the impedance adjustment pattern 15 is cut, the input impedance Z can be restored by restoring the length of the impedance adjustment pattern 15 by connecting the cut portions by soldering or the like.
[0044]
If the ratio L / W of the length L and the width W of the antenna element 14 is reduced, the characteristic curve of the input impedance Z shifts in the direction of the arrow C as shown in the graph of FIG. If the ratio L / W of the width W is increased, the characteristic curve of the input impedance Z shifts in the outer direction of the arrow B. Therefore, if the input impedance Z cannot be optimized only by changing the length of the impedance adjustment pattern 15, the ratio L / W of the length L and width W of the antenna element 14 is changed to change the input impedance Z. Then, the input impedance Z may be finely adjusted again by changing the length of the impedance adjustment pattern 15.
[0045]
FIG. 6 shows a modification of the dipole antenna of FIG. Here, the impedance adjustment pattern 15 a is disposed along the upper edge of the antenna element 14.
[0046]
FIG. 7 shows another modification of the dipole antenna of FIG. Here, the width of each antenna element 13, 14 is widened, and the impedance adjustment pattern 15 b is arranged along the right edge of the antenna element 14.
[0047]
FIG. 8 shows another modification of the dipole antenna of FIG. Here, the impedance adjustment pattern 15c is bent and arranged a plurality of times.
[0048]
6, 7, and 8, the area occupied by the impedance adjustment pattern is small, so that the dielectric substrate 12 does not need to be particularly large, and the dipole antenna 11 can be increased in size. You don't have to invite me.
[0049]
FIG. 9 shows still another modification of the dipole antenna of FIG. Here, a dielectric film 12 a is used instead of the dielectric substrate 12. Instead of the dielectric film 12a, a paper material, a glass material, or the like may be used.
[0050]
Even if the impedance adjustment pattern is provided on the antenna element 13 or the impedance adjustment pattern is provided on each of the antenna elements 13 and 14, the same effect can be achieved. Further, the input impedance Z of the dipole antenna 11 can be adjusted by connecting a plurality of impedance adjustment patterns to at least one of the antenna elements 13 and 14 and selectively changing the length of each impedance adjustment pattern. I do not care.
[0051]
In addition, the input impedance Z is determined according to the length of the impedance adjustment pattern regardless of the direction of the impedance adjustment pattern and the distance between the impedance adjustment pattern and the antenna element. It may be changed freely. Alternatively, the impedance adjustment pattern may be disposed on the back surface of the dielectric substrate 12.
[0052]
Further, the shape of each antenna element 13, 14 may be variously modified.
[0053]
Also, as an impedance adjustment pattern, a plurality of pattern pieces are arranged at intervals, and by connecting each pattern piece by soldering or the like, while forming an impedance adjustment pattern connected to the antenna element, The length of the impedance adjustment pattern may be adjusted.
[0054]
Further, the connection position of the impedance adjustment pattern with respect to the antenna element may be changed. However, since the potential in the vicinity of the feeding point of each antenna element 13 and 14 is low, even if the impedance adjustment pattern is connected to this portion and the length of the impedance adjustment pattern is changed, the input impedance Z is slightly It only changes. For this reason, it is preferable to connect the impedance adjustment pattern to the portion of the antenna element that is separated from the feeding point. In particular, if the impedance adjustment pattern is connected to the tip side from the middle point of the antenna element separated from the feeding point, the change of the input impedance Z with respect to the change of the length of the impedance adjustment pattern becomes large, and the adjustment of the input impedance Z Is extremely easy.
[0055]
Further, instead of mounting and connecting the IC chip 17 to the feeding point of the dipole antenna 11, another transmission / reception circuit or the like may be connected to the feeding point via a coaxial cable or the like. In portable electronic devices and the like, a method of drawing a coaxial cable or the like from the feeding point is more versatile than mounting the IC chip 17 directly on the feeding point of the dipole antenna 11.
[0056]
FIG. 10 is a block diagram showing an embodiment of the mobile object identification system of the present invention. The system of the present embodiment includes a plurality of tags 21-1 to 21-n and a read / write terminal device 22 that transmits and receives each data between the tags 21-1 to 21-n.
[0057]
Each tag 21-1 to 21-n has the dipole antenna 11 and the IC chip 17 shown in FIG. The IC chip 17 performs wireless communication through the dipole antenna 11 and transmits / receives data to / from the read / write terminal device 22. The IC chip 17 has a calculation function and a memory function, and can process and store data.
[0058]
In such a system, each tag 21-1 to 21-n is attached to each article (not shown), and the unique data of the article is attached to the article from the read / write terminal device 22 for each article. The tag information is transmitted to the IC chip 17 and the personal information of the article is stored in the IC chip 17. Also, for each article, the IC chip 17 of the tag attached to the article is called from the read / write terminal device 22, and the unique data of the article is transmitted from the IC chip 17 of the called tag, so that the unique information of the article Is received by the read / write terminal device 22.
[0059]
Thus, each article is managed by transmitting / receiving the unique data of each article between each of the tags 21-1 to 21-n and the read / write terminal device 22.
[0060]
In each of the tags 21-1 to 21-n, the length of the impedance adjustment pattern is adjusted to perform impedance matching between the dipole antenna 11 and the IC chip 17, and the input / output power of the IC chip 17 is maximized. Keep it. Thereby, it is possible to satisfactorily perform data communication between each of the tags 21-1 to 21-n and the read / write terminal device 22.
[0061]
The IC chip 17 includes an IC chip that receives power from a battery and an IC chip 17 that receives an electromagnetic wave signal and converts the received input into electric power.
[0062]
【The invention's effect】
As described above, according to the present invention, the impedance of the dipole antenna can be adjusted by cutting the impedance adjustment pattern in the middle and changing its length. Since the impedance adjustment pattern is a line having a narrower width than the antenna element, it can be easily cut, and even if its length is changed, it hardly affects the directivity characteristics of the antenna. .
[0063]
Further, since the impedance adjustment pattern is connected to the antenna element at a position away from the feeding point, the change in impedance with respect to the change in the length of the impedance adjustment pattern becomes clear, and the adjustment of the impedance becomes easy.
[0064]
Furthermore, since the impedance adjustment pattern is arranged along the antenna element on the dielectric, or the impedance adjustment pattern is arranged by bending a plurality of times on the dielectric, the occupied area of the impedance adjustment pattern is small, An increase in the size of the dipole antenna can be suppressed.
[0065]
In addition, since the cut adjustment mark is provided in the vicinity of the impedance adjustment pattern, the length of the impedance adjustment pattern of the plurality of dipole antennas can be adjusted uniformly, and the sensitivity of the dipole antenna becomes almost “0”. Adjustment is easy.
[Brief description of the drawings]
FIG. 1 is a plan view showing an embodiment of a dipole antenna of the present invention.
FIG. 2 is a side view showing the dipole antenna of FIG.
3 is a graph showing the relationship between the input impedance Z of the dipole antenna of FIG. 1 and the length t of the impedance adjustment pattern. FIG.
4 is a plan view illustrating a state in which the impedance adjustment pattern of the dipole antenna of FIG. 1 is cut in the middle thereof. FIG.
FIG. 5 is a graph showing the directivity characteristics of the dipole antenna of FIG.
6 is a plan view showing a modification of the dipole antenna of FIG. 1. FIG.
7 is a plan view showing another modification of the dipole antenna of FIG. 1. FIG.
FIG. 8 is a plan view showing another modification of the dipole antenna of FIG.
9 is a view showing still another modification of the dipole antenna of FIG. 1. FIG.
FIG. 10 is a block diagram showing an embodiment of the mobile object identification system of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Dipole antenna 12 Dielectric board | substrates 13 and 14 Antenna element 15 Impedance adjustment pattern 16 Metal film 17 IC chip 21-1 to 21-n Tag 22 Reading / writing terminal device

Claims (4)

In a dipole antenna in which a pair of antenna elements is formed as a pattern on a dielectric,
An impedance adjustment pattern having a width narrower than that of the antenna element, which is connected to at least one of the antenna elements at a position farther from the feeding point than the intermediate point of the antenna element and extends along the line from the connection position to the edge of the antenna element A dipole antenna characterized by the arrangement of   The dipole antenna according to claim 1, wherein a cutting adjustment mark is provided in the vicinity of the impedance adjustment pattern.   A tag using a dipole antenna, wherein a semiconductor chip for communicating data through the dipole antenna is connected to a feeding point of the dipole antenna according to claim 1. A mobile object identification system comprising the tag according to claim 3 and a read / write terminal device that transmits and receives data to and from the tag.

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