JP2000134028A - Planar directional antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a planar directional antenna which uses inexpensive material and has plural antenna elements by providing a power supply pattern extending to the feeding points of the plural antenna elements from a coaxial line feeding point and branching out on the other surface of a power supply substrate and providing stubs in the middles of the power supply pattern. SOLUTION: A power supply pattern branches striplines 24a and 24b and further branches the stripline 24a into two, striplines 25a and 25b are formed by being extended in a reverse direction and the stripline 24 is branched in order to connect four feeding points of a microstrip antenna. Thus, power is fed to the four feeding points of the microstrip antenna. A stub 25a is formed in the middle part of the stripline 24a, a stub 25b is also formed in the middle part of the stripline 24b so that the matching of the power supply pattern can be taken. Striplines in front from the stubs 25a and 25b are made wider than the feeding point sides of a coaxial cable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar antenna used in a high frequency range of 1 GHz to 6 GHz, and more particularly to a structure of a broadband antenna having directivity.

[0002]

2. Description of the Related Art Advances in communication technology have increased the demand for antennas that can handle high frequencies and have good directivity in the field of antennas. In general, the object is achieved by forming a plurality of antenna elements on a dielectric substrate, synthesizing signals received from the antenna elements, and branching a signal to be transmitted. In addition, a similar configuration is often adopted to cope with horizontal polarization or vertical polarization.

[0003] Since a dielectric substrate used for an antenna is required to have a predetermined dielectric constant and a high Q, the material is expensive. When a plurality of antenna elements are formed on a single substrate, the same material is used for a portion that does not operate as an antenna, which not only increases the cost but also makes it possible to manufacture a homogeneous dielectric substrate. It becomes difficult.

Further, it is necessary to form a radiation electrode of a microstrip antenna and a microstrip line for feeding on one surface of a dielectric substrate. Therefore, the design of the feed pattern is likely to be restricted, and if a mismatch occurs when a reactance element for matching is formed between the feed pattern and the antenna patch pattern serving as a load, the mismatch occurs with the radiation electrode of the microstrip antenna. Radio waves are radiated from the power supply pattern formed on the same surface.

[0005]

SUMMARY OF THE INVENTION The present invention provides a directional planar antenna having a plurality of antenna elements using inexpensive materials. It is another object of the present invention to provide a planar antenna that is easily subjected to impedance matching without being restricted by the design of a power supply pattern. It is another object of the present invention to provide a broadband planar antenna in a high frequency band.

[0006]

According to the present invention, a plurality of dielectric microstrip antennas are mounted on a two-layer printed circuit board having a feed pattern from a coaxial feed point to a feed point of a microstrip antenna, and The above problem is solved by improving the power supply pattern.

That is, in a planar antenna having a plurality of antenna elements on a feed board, a ground electrode is formed on almost one surface of the feed board, and a plurality of antennas are provided on the other surface of the feed board from a coaxial line feed point. It is characterized by having a power supply pattern extending to the power supply point of the element and branching, and having a stub in the middle of the power supply pattern.

More specifically, in a planar antenna having a plurality of antenna elements on a power supply board, the antenna element has a ground electrode connected to a ground electrode on the entire surface of the power supply board and a through-hole in the power supply board. The feed point and the feed pattern are connected to each other, and the feed pattern of the feed board extends from the coaxial feed point to the feed points of the plurality of antenna elements, and extends between the coaxial feed point and the branch point and between the branch point and the antenna. It is characterized in that a stub is provided in the middle of the power supply pattern between the element and the power supply point.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a power supply substrate, a commonly used double-sided printed circuit board is used. A ground electrode is formed on the entire surface on which the antenna element is mounted, and a power supply conductor pattern is formed on the opposite surface. The power supply conductor pattern is formed so as to branch from a power supply point connected to the coaxial cable and extend to a position corresponding to the power supply point of each antenna element, and a matching stub is formed in the middle thereof. . If this stub is formed symmetrically on both sides of the conductor pattern, the current will be in the opposite direction, so that the radiation can be canceled.

It is preferable that a metal plate is disposed so as to face the power supply conductor pattern, and that this metal plate be part of a case and be covered with a radome made of plastic or the like which is disposed on the antenna element and covers them.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing an example of a planar antenna according to the present invention, in which a microstrip antenna element is mounted on a printed circuit board. Printed wiring board 11
A conductor pattern for grounding is formed on almost the entire surface of the substrate, and a conductor pattern of a microstrip for power supply is formed on the back surface.

On the surface of the printed wiring board 11, four microstrip antennas 13 are mounted. These microstrip antennas 13 have a radiation electrode on the surface of the dielectric substrate, and a ground electrode on almost the entire back surface. The ground conductor pattern of the printed wiring board 11 and the ground electrode of the microstrip antenna 13 are connected by soldering or the like.
Is mounted on the printed wiring board 11. The feeding point 12 of the microstrip antenna 13 and the end of the feeding conductor pattern of the printed wiring board 11 are connected to the feeding point of the microstrip antenna. The ground electrode of the microstrip antenna may be connected capacitively via a double-sided adhesive tape.

The printed wiring board 11 is fixed to a metal plate case 15 by screwing or the like. Coaxial cable 17 is the case
It is drawn inside through 15 and the printed wiring board at the feeding point
11 is connected to the power supply pattern on the back surface. After the assembly, the radome is put on.

FIG. 2 is a bottom view of the printed wiring board 11. A feeding point is formed at the central portion and connected to the end of the coaxial cable. In order to connect to the feed points 12 of the four microstrip antennas 13 shown in FIG. ,
25b is formed by extending in the opposite direction, and the strip line 24b is branched into strip lines 25c and 25d. As a result, power is supplied to the feeding points of the four microstrip antennas.

A stub 25a is formed at an intermediate portion of the strip line 24a, and a stub 25b is also formed at an intermediate portion of the strip line 24b to match a power supply pattern. The width of the strip line beyond these stubs 25a and 25b is wider than the feed point side of the coaxial cable.

Further, the strip lines 26a and 26 are branched.
Similarly, b, 26c, 26d also have stubs 27a, 27b, 27
c and 27d are formed and matched, and the width of the line is similarly varied. Since the impedance of the line changes depending on the shape and size of these stubs, the impedance can be adjusted by removing this pattern or adding a conductor. It is desirable that these stubs are formed symmetrically with respect to the strip line.

Hereinafter, the characteristics of the antenna having the above-described feed pattern formed by the conductor pattern will be described. A Smith diagram of the antenna according to the present invention was observed by a network analyzer. FIG. 3 shows the result.

As shown in FIG. 3, the drawn arc rotates multiple times near the center of the figure, and as shown by the return loss characteristic shown in FIG. 4 and the SWR characteristic shown in FIG. Wide characteristics are realized.

It should be noted that the shape of the stub is not limited to the above, and can be used when the number of elements of the antenna changes.

[0021]

According to the present invention, it is sufficient to use an expensive dielectric substrate only for the antenna element, and the other parts can be provided by an inexpensive printed circuit board. In addition, the design of the power supply pattern is not restricted, and the size of the printed circuit board can be reduced. There is also an advantage that the characteristics of the microstrip antenna can be measured before mounting.

The planar antenna according to the present invention facilitates impedance matching and has extremely good characteristics enabling wide band.

Further, the planar antenna according to the present invention has an advantage in that unnecessary radiation hardly occurs and good characteristics are easily maintained.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a bottom view showing an embodiment of the present invention.

FIG. 3 is an explanatory diagram of characteristics of a planar antenna according to the present invention.

FIG. 4 is an explanatory diagram of characteristics of a planar antenna according to the present invention.

FIG. 5 is an explanatory diagram of characteristics of a planar antenna according to the present invention.

[Explanation of symbols]

 12: Feeding point 13: Microstrip antenna 24, 26: Strip line 25, 27: Stub

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Naoaki Tsuda 18 Gomigaya, Tsurugashima-shi, Saitama F-term (reference) 5J021 AA04 AA05 AA09 AA11 AB06 CA03 DB02 DB03 FA32 HA05 HA07 JA07 5J045 AA01 AA02 AB05 AB06 DA10 EA07 FA02 HA03 JA04 JA12 LA01 MA07 NA01

Claims (3)

[Claims] In a planar antenna having a plurality of antenna elements on a feed board, a feed pattern extending from a coaxial feed point to a feed point of the plurality of antenna elements on one surface of the feed board and branching is provided. A flat antenna comprising a stub. 2. A planar antenna having a plurality of antenna elements on a feed board, the feed board comprising a feed pattern extending from a coaxial feed point to a feed point of the plurality of antenna elements on one surface of the feed board and branching. A flat antenna comprising a stub in the middle of a power supply pattern between the power supply point and the branch point and between the branch point and the power supply point of the antenna element. 3. A planar antenna having a plurality of antenna elements on a power supply board, wherein the antenna element has a ground electrode connected to a ground pattern on the surface of the power supply board, and a power supply point and a power supply point via a through hole in the power supply board. The feed pattern of the feed board is connected to the feed pattern, and the feed pattern of the feed substrate branches from the coaxial feed point to the feed points of the plurality of antenna elements and extends. A flat antenna comprising a stub in the middle of a feeding pattern between the two.