JP2000278031A - Antenna for small-sized dielectric tag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an antenna for a small-sized dielectric tag small in size. SOLUTION: Microstrip lines 12a, 12b, 12c, 12d, 12e, 12f and microstrip line discontinuous parts 13a, 13b, 13c, 13d, 13e are connected sequentially in the order of the line 12a, the part 13a, the line 12b, the part 13b,..., the line 12e, the part 13e, and the line 12f. An electromagnetic wave excited from a feeding point 15a reaches a tip of a transmission line of a 2nd layer connected by a through-hole 15c via an exciting conductor consisting of the microstrip lines and the microstrip line discontinuous parts. Thus, this configuration exhibits a characteristics of the antenna.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna used for wireless communication and the like, and more particularly to an antenna for a small dielectric tag used for a non-contact information tag.

[0002]

2. Description of the Related Art In recent years, cards such as commuter passes and telephone cards have become widespread, but most of them are contact cards represented by magnetic cards. At present, such a card system is moving from a contact type card such as a magnetic card to a wireless non-contact type card.

In a non-contact type card (hereinafter, referred to as a non-contact tag), various circuit patterns are formed on the surface of a dielectric substrate, and have a multilayer structure. Non-contact tags
It is desired to reduce the thickness and size of the antenna, and it is also required to reduce the size of the antenna for a small dielectric tag used for such a non-contact tag.

[0004] A conventional small dielectric tag antenna will be described. FIG. 3 is a plan view of a conventional small dielectric tag antenna. The conventional small dielectric tag has a dielectric 31
And a coil 3 in which a conductor is formed in a spiral shape on a dielectric 31
And 2. The coil 32 is a transmission line having a winding formed on the same plane, and is planarly mounted on the dielectric 31.

[0005]

However, the conventional small dielectric tag antenna has a problem that miniaturization is difficult.

In the above-described antenna for a small dielectric tag, the antenna is usually configured with a transmission line length of ４λ with respect to the wavelength λ of the operating frequency. In the case of miniaturization, a complicated structure has to be obtained, for example, a base material having a transmission line formed on a dielectric material has a multi-layer structure, and through holes for connecting upper and lower transmission lines are provided. For this reason, it was not easy to reduce the size.

[0007] In particular, the lower the applied frequency, the more the multilayer structure must be used, resulting in an increase in size.
There is a problem that the price is high due to the complicated multilayer structure. In addition, in order to realize miniaturization, it is necessary to shorten the line length of the antenna, which is determined by the length of the used electrical length and the constant of the shortening rate, as much as possible. For this reason, if the conductor width is to be reduced to several tens of microns or less, there is a problem that the characteristic impedance of the transmission line increases and it is not possible to realize small antenna characteristics.

The present invention has been made in view of the above points, and has as its object to provide a small-sized dielectric tag antenna which can be easily reduced in size.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a small-sized dielectric tag antenna used for a non-contact information tag, wherein the antenna comprises a flat antenna formed on the surface of a dielectric substrate. A non-continuous line in which a line includes a first transmission line portion having a predetermined characteristic impedance of the line and a second transmission line portion having a characteristic impedance different from that of the first transmission line portion. An antenna for a small dielectric tag, which is a transmission line having a characteristic, is provided.

[0010] The antenna for a small-sized dielectric tag having such a configuration has a physically non-continuous structure having a first transmission line portion and a second transmission line portion having different characteristic impedances on the surface of a dielectric substrate. Is formed. A capacitor and an inductance are formed in accordance with the magnitude of the characteristic impedance of the line, a low-pass filter including L and C is formed, and the transmission line operates as an excitation antenna.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are plan views of an antenna for a small dielectric tag according to an embodiment of the present invention. FIG. 1 is a plan view of the first layer, and FIG. 2 is a plan view of the second layer.

First, the configuration of the first layer of the antenna for a small dielectric tag according to the embodiment of the present invention shown in FIG. 1 will be described. The first layer forms the transmission conductor of the microstrip antenna (MSA) on the plane of the rectangular parallelepiped dielectric 11. More specifically, Cu or Al having a conductor height of 1 oz or 1/2 oz, or Ag, Au or another material,
The transmission conductor is formed.

The microstrip antenna made of such a material forms a coil on the plane of the dielectric 11. The coil includes a first transmission line having a characteristic impedance of a predetermined line, and a second transmission line having a characteristic impedance different from that of the first transmission line. The first transmission line section includes microstrip lines 12a and 12a having a predetermined line width.
b, 12c, 12d, 12e, and 12f. Further, the second transmission line section has a line width different from those of the microstrip lines, and is a microstrip line discontinuity section 13 which is a physical discontinuity point of the microstrip line.
a, 13b, 13c, 13d, and 13e. Microstrip lines 12a, 12b, 12c, 12d, 1
2e, 12f, microstrip line discontinuity 1
3a, 13b, 13c, 13d, 13e alternately represent 1
2a, 13a, 12b, 13b, ..., 12e, 13e,
12f, in this order. Further, a microstrip line terminal line 14 is provided in parallel with the microstrip line 12a. Further, the microstrip lines 12a, 12f, 14 are provided with through holes 15a, 15b, 15c.

The microstrip lines 12a, 12
b, 12c, 12d, 12e, and 12f form inductors at portions where the characteristic impedance of the line is large.
Microstrip line discontinuities 13a, 13b, 1
3c, 13d and 13e are portions where the characteristic impedance of the line is small and form a capacitor. Since the microstrip lines and the microstrip line discontinuities are alternately arranged, a low-pass filter composed of L and C is formed. In the microstrip antenna, a low-pass filter formed by this combination is formed in multiple stages, and operates as an excitation antenna.

The through hole 15a is a feed point provided at the end of the microstrip line 12a. The through-hole 15b is provided at the end of the end line 14 of the microstrip line. Through hole 15c
Is provided at an end of the microstrip line 12f and connects the microstrip line 12f of the first layer to the second layer.

The terminal line 14 of the microstrip line is an antenna transmission line provided in parallel from the feed point 15a to the point X, and is used for correcting the antenna impedance as viewed from the feed point 15a.

Next, the structure of the second layer shown in FIG. 2 will be described. Similarly to the first layer, the second layer has a rectangular parallelepiped dielectric 21.
The transmission conductor of the microstrip antenna (MSA) is formed on the plane of the. The transmission lines are microstrip lines 22a, 22b, 22 that are the first transmission lines.
c, 22d, and microstrip line discontinuities 23a, 23b, 23c, 23d as second transmission lines,
It is composed of Micro strip line 22
a, 22b, 22c, 22d and the microstrip line discontinuities 23a, 23b, 23c, 23d alternately form 23a, 22a, 23b,..., 22c, 23d, 2
2d, in this order. The microstrip line discontinuous portion 23a is connected to the microstrip line 12f of the first layer via the through hole 15c.
The end of the final microstrip line 22d is an open line. By making the tip open, the transmitted radio wave is more easily excited.

The back surface of the microstrip antenna has a ground structure except for the feeding point. The operation of the antenna for a small-sized dielectric tag having such a configuration will be described. The electromagnetic wave excited from the feeding point 15a reaches the tip of the second-layer microstrip line 22d via the excitation conductor including the microstrip described above, and exhibits characteristics as an antenna. The antenna transmission line from the feed point 15a of such a microstrip antenna to the open end line of the microstrip antenna has five discontinuous points on the first layer and four discontinuous points on the second layer. ing. By making the discontinuous points multi-stage, the length of the electric line as the antenna can be shortened.

As described above, a capacitor having a small characteristic impedance of the line is provided on the microstrip antenna line to form a capacitor, and an inductor is formed by providing a large characteristic impedance of the line on the microstrip antenna line. The line length of the portion where the characteristic impedance is changed is λg / 8 of the frequency to be handled.
(Λg: signal wavelength in the transmission line)

[0020]

Tanβι = 1 (1), and reactance is formed. At this time, β represents the phase constant, and ι represents the line length of the strip line.

As described above, since the low-pass filter composed of L and C can be formed on the microstrip antenna line, the excitation antenna can be easily operated on the dielectric structure having two or more layers. In particular, in the case of an antenna having a long wavelength, if all the low-pass filters are formed in one layer, the effect of electromagnetic radiation between the antenna patterns is large, and the antenna cannot operate efficiently. In order to eliminate this adverse effect, the low-pass filter can be easily divided into two or more layers. Further, by drawing all the antenna patterns on one layer, it is possible to prevent the lines and antenna conductors from becoming finer, thereby increasing the conductor loss and the line-to-line capacitance, thereby reducing the radiation efficiency.

Further, in the case of a configuration in which the end installation line 14 of the microstrip line is not provided, it may not always be possible to efficiently excite. Returning to FIG. An antenna transmission line between 15b and Y, here a termination line 14 of the microstrip line, is formed in parallel with a feeding point 15a and X in the microstrip line 12a, and a floating line between 15a and X and 15b and Y. By adjusting the capacitance and electromagnetic coupling and the length of the transmission line between 15b and Y, the antenna impedance seen from the feeding point 15a is corrected, and the input impedance on the tuner side is matched. In the microstrip antenna according to one embodiment of the present invention, the input section matching line is thus configured.

In the above description, a feeding point is provided on the first layer,
Although the open-end line of the microstrip line of the second layer is provided, the first layer and the second layer may be reversed. In the above description, a two-layer structure of five layers and four layers has been described. However, a desired structure such as two layers and four layers can be obtained according to the application.

[0024]

As described above, according to the present invention, a physically discontinuous transmission line having different characteristic impedances is formed on the surface of the dielectric substrate. By forming a capacitor and an inductance according to the magnitude of the characteristic impedance of the line, the low-pass filter composed of L and C operates as an excitation antenna. Since the transmission line having such discontinuity can be easily formed in a plurality of discontinuous points or divided into two or more layers, antenna characteristics can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a small dielectric tag antenna (first layer) according to an embodiment of the present invention.

FIG. 2 is a plan view of a small dielectric tag antenna (second layer) according to an embodiment of the present invention.

FIG. 3 is a plan view of a conventional small dielectric tag antenna.

[Explanation of symbols]

11, 21 ... dielectric, 12a, 12b, 12c, 12
d, 12e, 12f... microstrip line (first
Layers), 13a, 13b, 13c, 13d, 13e... Microstrip line discontinuities (physical discontinuities of the first layer microstrip lines), 14... Microstrip line terminal lines, 15a, 15b, 15c
... through holes, 22a, 22b, 22c, 22d ... microstrip lines (second layer), 23a, 23b,
23c, 23d: discontinuous portion of microstrip line (physical discontinuous point of second layer microstrip line)

Claims (4)

[Claims] 1. A small dielectric tag antenna used for a non-contact information tag, wherein the transmission line forming the antenna formed in a plane on the surface of the dielectric substrate has a characteristic impedance of the line having a predetermined magnitude. 1
And a second transmission line section having a characteristic impedance different from that of the first transmission line section, and a discontinuous transmission line provided with: Antenna. 2. The transmission line having discontinuity, wherein a discontinuous portion formed by the first transmission line portion and the second transmission line portion is provided in multiple stages.
The antenna for a small dielectric tag described in the above. 3. The antenna according to claim 1, wherein the discontinuous transmission line is formed by dividing into multiple layers. 4. The antenna for a small dielectric tag according to claim 1, wherein an end of said transmission line is an open type.