JPH09148838A - Micro strip antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an antenna which is suitable as the radio base station antenna in a mobile communication system, is simple in constitution and is easy to be manufactured. SOLUTION: On the surface of a dielectric plate 1 which is thinner than a radiation wave length, an exciting element 2 adhering/forming a metal film in a loop-shaped circuit is provided. At proper space in the forward, backward or the both of the forward and backward sides of the dielectric plate 1, other dielectric plate group 10, etc., are provided in parallel. At this stage, further, a parasitic exciting element group adhering/forming the metal film in shapes such as a circle, a rectangle or a loop-shaped circuit, etc., is provided on the surface. The relative location of the both parties is selected so that the electromagnetic waves emitted from the exciting element 2 may be affected by the parasitic exciting element 4, and a power feeding line 3 and a matching line are provided. As a result, the directivity, the characteristic impedance and the resonance wavelength that the antenna has become possible to be changed and the design/manufacture becomes easy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna for a wireless communication system, and more particularly to an antenna suitable for use as a wireless base station antenna for a mobile communication system.

[0002]

2. Description of the Related Art Various antennas are used as radio base station antennas in mobile communication systems. For example, a collinear antenna is used for a PHS system, which is a typical mobile radio system in Japan. Other,
Brown antennas, sleeve antennas, etc. are also used. These antennas are called linear antennas, and are a form in which electromagnetic waves are transmitted from a linearly formed exciting element, and most of them are currently in this form. With the recent advent of high-quality and inexpensive dielectric plates, the above-mentioned antennas have been used as linear antennas of the type in which a metal film is deposited on the surface of the dielectric plate-usually called microstrip antennas. ing. On the other hand, there is an antenna type called "folded dipole antenna" in which the tips of the dipole antennas are connected to each other and one of these dipoles is fed in the center. Generally, an antenna that forms an electric circuit in which the entire antenna is closed when viewed from the power feeding section is called a loop antenna, but a "folded dipole antenna" also falls within this category. The "folded dipole antenna" is also widely used in amateur radio and special communications. However, it does not seem to be used as a radio base station antenna for mobile communication systems.

[0003]

The "folded dipole antenna" (hereinafter abbreviated as loop antenna) is not used as a radio base station antenna of a mobile communication system for the following reason. It is difficult to obtain an antenna having a high gain. When the frequency used is given, the total length of the antenna that resonates with it is determined, and the antenna length cannot be changed to an arbitrary value. Given the shape of the antenna, its characteristic impedance is fixed and cannot be changed. Therefore, the cable feeding the antenna must be chosen so that the characteristic impedance of the cable matches that of the antenna. The shape of the antenna usually has to be included in a two-dimensional plane, and the directional characteristics of the electromagnetic wave transmitted from the antenna are determined according to the shape, so in order to obtain arbitrary directivity, Other circuits / means must be used. The weather resistance of the antenna is inferior to that of the linear antenna. In a nutshell, the above items are difficult to use,
Some improvement was desired.

[0004]

In order to improve the electrical characteristics of the solid loop antenna (folded dipole antenna) described above, the present invention uses a recent good-quality and inexpensive dielectric plate, and has a metal film on the surface thereof. Was formed into a circular, rectangular, or loop-shaped circuit shape, and was attached to form an excitation element, thereby forming a microstrip antenna. Further, another dielectric plate group is provided in parallel in front of or behind the dielectric plate, or both in front of and behind the dielectric plate at an appropriate interval.
A parasitic excitation element group in which a metal film was deposited / formed on a loop circuit was set on the surface. Then, by selecting the relative positions of the two so that the electromagnetic wave emitted from the excitation element is affected by the parasitic excitation element, various characteristics originally possessed by the loop circuit can be changed. In addition, the disadvantage that the weather resistance is inferior to the conventional linear antenna is that the operating frequency is high frequency of 1 GHz or more (hence the wavelength is 30 c
m or less), and the size of the entire antenna can be reduced, which can be solved by covering the entire antenna with a resin material from the outside.

[0005]

In the antenna of the present invention, another dielectric plate group is formed in parallel in front of or behind the loop-shaped microstrip excitation element formed on the surface of the dielectric plate, or at both front and rear, with an appropriate interval. Provided on the surface, a parasitic excitation element group, in which a metal film is attached / formed in a circular, rectangular or loop-shaped circuit shape, is installed, and the electromagnetic waves emitted from the excitation element are affected by the parasitic excitation element. Since the relative positions of the two are selected so as to be received, the emission characteristics of the electromagnetic wave originally possessed by the loop-shaped excitation element are changed. To undergo a change means to obtain an electrical characteristic that cannot be provided conventionally without changing the apparent physical size of the loop antenna.
The degree of change described above includes the distance between the dielectric plate on which the loop-shaped excitation element is adhered and another dielectric plate installed in parallel with the dielectric plate, the number of dielectric plates, and another dielectric plate. Various aspects are exhibited depending on the shape of the parasitic excitation element provided on the body plate, the relative position to the loop-shaped excitation element, and the like. That is, as the installation condition of the parasitic excitation element, the condition that is greatly affected by the resonance wavelength (resonance frequency) of the antenna,
There are various conditions such as the condition affected by the characteristic impedance, the condition affected by the change in the directivity characteristic, the condition affected by both of the above-mentioned two, and the condition affected by the above-mentioned all three.

[0006]

1 (a) is a plan view showing an embodiment of an exciting element of a microstrip antenna according to the present invention. That is, the figure shows the loop-shaped excitation element of the present invention as viewed from above vertically, where 1 is a dielectric plate that is thinner than the wavelength of the radiated electromagnetic wave, 2 is an excitation element, and 3 is a feeder line. FIG. 1B shows a dielectric plate on which a loop-shaped excitation element is attached and formed, and another dielectric plate 10 is provided in parallel in front of the dielectric plate with an appropriate interval.
FIG. 4 is a diagram of the parasitic excitation element 4 provided on the dielectric plate and viewed from above. Regarding the relative positional relationship between the loop-shaped excitation element 2 and the parasitic excitation element 4, the shape of the loop-shaped excitation element 2 and the parasitic excitation element 4 is regarded as a rectangle, and the straight line connecting the intersections of the two diagonal lines is the dielectric plate. It is assumed that it is installed so as to intersect with 1 vertically.

The results of measuring the characteristics of the prototype antenna of the present invention will be described below. The actual dimensions of the loop antenna element shown in FIG. 1A are 4.8 cm in width (longitudinal direction of the dielectric plate), 2.6 cm in length, and about 14.8 cm in total length, and theoretical calculation shows that the loop antenna has characteristics. It is estimated that the impedance is about 50 ohms and the resonance wavelength (resonance frequency) is about 15.5 cm, (about 1.93 GHz). In addition, the loop-shaped parasitic excitation element 4 shown in FIG.
2 is as shown in FIG.

FIG. 3A shows the standing wave ratio of the antenna originally possessed by the loop-shaped excitation element. That is, there is an original standing wave ratio (SWR) characteristic when there is a loop-shaped microstrip antenna formed on the surface of the dielectric plate 1 and there is no parasitic excitation element or the like in the vicinity thereof.
The standing wave ratio mentioned here indicates the ratio of the input wave and the reflected wave at the antenna feeding terminal point. The marker 1 has 1.9 GHz, the standing wave ratio at this point is 1.2621, and the marker 2 has 2.1 GHz.
Hz, the standing wave ratio at this point is 1.8732, the marker 3 is 1.7 GHz, and the standing wave ratio at this point is 4.0269. 3 (b) shows that the parasitic excitation element 10 shown in FIG. 1 (b) is 0.8 cm of the dielectric plate 1 (thickness 1.0 mm).
The standing wave ratio of the antenna when present in the front is shown. As is clear from the figure, the resonance frequency is 0.05 GHz.
Frequency is 2.1GHz, and 1.7GHz
It can be seen that the standing wave ratio in Fig. 3 is larger than the value in Fig. 3 (a). As a result, it can be seen that the presence of the parasitic excitation element 10 shown in FIG. 1B changes the resonance frequency originally possessed by the loop-shaped excitation element and narrows the band. Also, in this case, it was found that the directivity of the antenna becomes sharp, and therefore the antenna gain (horizontal direction in this case) increases (drawing omitted).

The shape of the parasitic excitation element is not always shown in FIG.
It does not have to have a loop-shaped release terminal as shown in (a). FIG. 2B is a plan view showing an example of a closed loop shape (hatched portion 5). The dimensions in this case are as shown in FIG. The loop circuit shown by the broken line shows the loop antenna element 2 of FIG. 1A, and the relative position with respect to the parasitic excitation element 5 is clarified. FIG.
The standing wave ratio characteristic of the antenna when the parasitic excitation element 5 having the shape shown in (b) is installed in the place shown in the parasitic excitation element 4 in FIG. 1 (b) is shown in FIG. 3 (c). As is apparent from FIG. 3C, in this case, the characteristic impedance originally possessed by the loop-shaped excitation element 2 is changed (from 50 ohm to a high value).

FIG. 2C shows a window type parasitic excitation element 1
A plan view is shown as an example. The dimensions in this case are as shown in FIG. The loop circuit shown by the broken line is shown in FIG.
The loop antenna element 2 is shown, and the relative position with the parasitic excitation element 6 is clarified. FIG. 3 shows the standing wave ratio characteristic of the antenna when the parasitic excitation element 6 having the shape shown in FIG. 2C is installed at the place shown in the parasitic excitation element 4 of FIG. 1B.
It shows in (d). As is clear from FIG. 3D, in this case, the characteristic impedance originally possessed by the loop-shaped excitation element is little changed, but the resonance frequency is changed to a large low frequency.

As described above, it has been clarified that the presence of the parasitic excitation element changes variously the electric characteristics originally possessed by the loop-shaped excitation element. The presence of the body plate and the relative relationship between the loop-shaped excitation element and the parasitic excitation element makes it possible to provide the following characteristics. If a plurality of dielectric plates of the same kind are further installed in front of the dielectric plate 10 shown in FIG. 1 (b), and the parasitic excitation element shown in FIG. 1 (b) is deposited / formed on each dielectric plate, It is possible to further increase the directivity in the horizontal plane originally possessed by the antenna. Further, when a plurality of dielectric plates of the same type as the front are installed behind the dielectric plate 1 and the parasitic excitation element shown in FIG. 1 (b) is attached / formed on each dielectric plate, a large front and rear direction is obtained. An antenna having directional characteristics can be obtained.

The position of the parasitic excitation element provided on the dielectric plate 10 shown in FIG. 1B is slightly lowered, that is, in the plan view, the center of the parasitic excitation element is below the center of the loop-shaped excitation element. It has been experimentally confirmed that the main directional characteristics of the antenna can be directed downward when the antenna is installed so as to come to. As a result, when it is desired to direct the main directional characteristics of the antenna upward, the dielectric plate 10 shown in FIG.
It suffices to slightly raise the position of the parasitic excitation element provided in the above.

[0013]

Since the antenna of the present invention can change the characteristic impedance, resonance frequency and directivity peculiar to the antenna, it is easy to match the antenna and the feed line, and the antenna design is facilitated. It becomes possible to easily miniaturize. Therefore, the effect of the present invention is great.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a diagram showing various characteristics of the antenna of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dielectric plate 2 Excitation element 3 Feed line 4-6 Shape of parasitic excitation element 10 Dielectric plate

Claims (4)

[Claims] 1. An exciter element having a loop-shaped circuit formed with a metal film adhered to the surface of a dielectric plate that is thinner than the emission wavelength, and an appropriate distance in front of or behind the dielectric plate, or both before and after. There is another group of dielectric plates parallel to each other, and there is a parasitic excitation element group in which a metal film is attached / formed on the surface in a circular, rectangular or loop-shaped circuit shape,
A microstrip antenna characterized in that an electromagnetic wave emitted from the excitation element is influenced by the parasitic excitation element group. 2. An exciter element having a loop-shaped circuit formed of a metal film adhered to the surface of a dielectric plate that is thinner than the emission wavelength, and an appropriate distance in front of or behind the dielectric plate, or both before and after. There is another group of dielectric plates parallel to each other, and there is a parasitic excitation element group in which a metal film is attached / formed on the surface in a circular, rectangular or loop-shaped circuit shape,
A microstrip antenna capable of changing the directional characteristic originally possessed by the loop circuit by configuring the electromagnetic wave emitted from the exciting element to be influenced by the parasitic exciting element group. 3. An exciting element having a loop-shaped circuit formed with a metal film adhered to the surface of a dielectric plate that is thinner than the emission wavelength, and an appropriate distance in front of or behind the dielectric plate, or both before and after. There is another group of dielectric plates parallel to each other, and there is a parasitic excitation element on the surface of which a metal film is adhered / formed in a circular, rectangular or loop-like circuit shape. A microstrip antenna capable of changing the characteristic impedance originally possessed by the loop circuit by configuring such that a part of the emitted electromagnetic wave is affected by the parasitic excitation element. 4. An exciter element having a loop-shaped circuit formed of a metal film adhered to the surface of a dielectric plate group, which is thinner than the emission wavelength, and the front and rear or front and rear of the dielectric plate group. Another dielectric plate group is provided in parallel with a certain interval,
There is a parasitic excitation element on the surface of which a metal film is deposited / formed in a circular, rectangular or loop-shaped circuit shape,
A microstrip antenna capable of changing a resonance frequency originally possessed by the loop-shaped circuit by configuring a part of electromagnetic waves emitted from the excitation element to be influenced by the parasitic excitation element.