JPH08204431A - Multi-resonance antenna device - Google Patents

Abstract

PURPOSE: To attain multi-resonance without using any multi-resonance matching circuit and to provide a satisfactory directivity and both polarization radiation characteristics in the direction along a wall when the device is mounted on the surface of the wall. CONSTITUTION: This antenna device is a loop antenna folded in a U-shape, and both parallel parts 1a, 2a of an L-shape element and a center element 3 are set at λ/2 (λ: fundamental resonance wavelength of antenna), and orthogonal parts 1b, 2b are set at λ/4. The terminal part of the orthogonal part 1b is connected to a coaxial feed line 6, and that of the orthogonal part 2b to a ground metallic plate 5. An L-shape branch element 4 (or linear branch element 4') is connected to a point within 0.3λfrom the center element 3 or an L-shape element 2 on its extension, therefore, a second resonance frequency different from a reference resonance frequency is set. The length of the branch element is decided depending on the size of the element. Further multi-resonance can be obtained by increasing the number of branch elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-resonant antenna device which emits strong radiation in the lateral direction of the antenna, emits both vertical and horizontal polarized waves, and has a small and wide band characteristic. In particular, it is suitable as an antenna for a small base station attached to an indoor wall or the like.

[0002]

Prior Art and Problems to be Solved by the Invention FIG.
Is an example of a conventional multi-resonant antenna device. A is a top load type whip antenna that is downsized and has multiple resonances by a matching circuit. B is an inverted L-shaped antenna that radiates both polarized waves and has two elements for multiple resonances. It is intended. Here, 101 is a linear whip element, 102 is a disk-shaped top load element, 103 is a multi-resonance matching circuit, 104 is a ground plane, 105 is a feed line, 107 is a vertical element of an inverted L-shaped antenna, and 108 is the same horizontal element. A and 109 are the same horizontal element B. These are all small multi-resonant antennas, but they have the following drawbacks.

In the antenna of FIG. 15A, the whip antenna is miniaturized by using a top load, but the radiation directivity is almost the same as that of the whip antenna. Therefore, the polarized wave becomes a linear polarized wave in the same direction as the whip element, and when this antenna is used as a base station, if the polarized wave of the portable device does not match this polarized wave, the reception level drops significantly. Further, since the radiation pattern is not radiated in the element direction of the whip element, if there is a portable device in that direction, radio waves from the portable device cannot be received. Since a multi-resonance matching circuit is used to achieve multi-resonance, this causes a loss and also lowers the reception level.

The antenna shown in FIG. 15B has two elements of an inverted L antenna so as to achieve two resonances. In this case, since there are the vertical element 107 and the horizontal element 108/109, both polarized waves are radiated, and two resonances are performed by the element, so that the loss is relatively small. However, since the radiation directivity is an inverted L-shaped antenna, when it is installed on a wall or the like, a strong reception level cannot be obtained because it does not radiate strongly in the direction along the wall.

For these reasons, the conventional multi-resonance antenna device cannot secure a desired service area when it is used as a base station antenna installed on a side surface such as a wall. The present invention solves such a problem, it is possible to achieve multi-resonance without using a multi-resonance matching circuit, and when this antenna is used as a base station antenna installed on a side surface such as a wall, The purpose is to obtain good radiation directivity and dual polarization characteristics along the wall.

[0006]

[Means for Solving the Problems]

(1) The multi-resonant antenna device according to claim 1 is a U-shaped antenna element (the lengths of two opposite sides and an intermediate side are approximately λ / 2; λ is a wavelength of a fundamental resonance frequency of the antenna).
Are arranged on a parallel plane that is separated from the ground metal plate by approximately λ / 4, and the ends of the two opposite sides are bent at substantially right angles to the ground metal plate side and extended to the vicinity of the ground metal plate. Are the first and second L-shaped elements, and are opposed to each other.
The side between the sides is the central element.

The end portion of the first L-shaped element is connected to the core wire of the coaxial power supply line led out through the small hole of the ground metal plate,
The outer conductor is connected to the ground metal plate, and the end of the second L-shaped element is connected to the ground metal plate. First and second
A linear branch element parallel to the ground metal plate of the L-shaped element and having a length of λ / 2 or less, or a part parallel to or right-angled to the ground metal plate of the first and second L-shaped elements, respectively. A second L-shaped element having at least one L-shaped branch element which is parallel and has a parallel portion having a length of approximately λ / 2 and an orthogonal portion having a length of λ / 4 or less, the central element or an extension thereof. Is connected to a point within 0.3λ, whereby at least one resonance frequency different from the fundamental resonance frequency is set.

(2) A multi-resonant antenna device according to claim 2 is
A U-shaped antenna element (the lengths of the two opposite sides and the middle side are approximately λ / 2; λ is the wavelength of the fundamental resonance frequency of the antenna) is a parallel plane that is approximately λ / 4 away from the ground metal plate. It is arranged on the upper side, and the end of one of the two opposite sides is bent substantially at right angles to the ground metal plate,
The first L-shaped element is extended to the vicinity of the ground metal plate, and the end portion of the other side is bent substantially at a right angle to the ground metal plate side and extended by a predetermined length (within λ / 4) to form the second L element. The element is a shaped element, and the side between the two opposite sides is the central element.

An end portion of the first L-shaped element is connected to a core wire of a coaxial power supply line led out through a small hole of a ground metal plate,
The outer conductor is connected to the ground metal plate. The end portion of the second L-shaped element is connected to the core wire of the terminal short-circuit line having a guide wavelength of λ / 2, and its outer conductor is connected to a point on the ground metal plate where the extension line of the end portion of the second L-shaped element intersects. Thus, the second resonance frequency different from the basic resonance frequency is set.

(3) According to the invention of claim 3, in the above (2), a linear branch element parallel to a portion of the first and second L-shaped elements parallel to the ground metal plate and having a length of λ / 4 or less, Alternatively, the first and second L-shaped elements may be parallel to the ground metal plate or to the right-angled part, respectively, and may be formed of a parallel portion having a length of approximately λ / 2 and an orthogonal portion having a length of λ / 4 or less. The shape branching element is connected to the central element or an extension thereof at a point within 0.3λ from the second L-shaped element, whereby a third resonance frequency different from the fundamental and second resonance frequencies is set.

(4) In the invention of claim 4, in the above (2), the termination short-circuit line is an L-shaped coaxial line which is bent and extended in a direction along the ground metal plate at a connection point with the ground metal plate. Composed. (5) In the invention of claim 5, in the above (1) or (2), approximately 1 wavelength of a resonance frequency different from the fundamental resonance frequency is provided in the middle of the first or second L-shaped element or the central element.
A phase adjustment line or a phase adjustment circuit having an electric length of / 2 is connected.

(6) In the invention of claim 6, in any one of (1) to (5), the first and second L-shaped elements and the linear (or L-shaped) branch element and the ground metal plate are provided. A dielectric or an insulator is inserted between them.

[0013]

【Example】

(Embodiment 1) FIG. 1 shows an embodiment of the invention of claim 1,
The antenna resonates at two frequencies and has good radiation characteristics as a wall-mounted base station antenna. Here, 1 and 2 are L-shaped elements, 3 is a central element, 4 is an L-shaped branch element,
Reference numeral 4'denotes a linear branch element, each made of metal, 5 a ground metal plate, 6 coaxial feed lines, 1a, 2a, 4a parallel parts parallel to the ground metal plate, 1b, 2b, 4b ground metal It is an orthogonal part perpendicular to the plate.

When the wavelength of the fundamental resonance frequency of the antenna is λ, the lengths of the parallel portions 1a and 2a and the central element 3 are approximately λ / 2, and the orthogonal portions 1b and 2b are approximately λ / 4. L-shaped branch element 4 connected to the central element 3 or an extension thereof
Alternatively, the length of the linear branch element 4'is determined by the second resonance frequency, as will be described later. As an example, an antenna device having dimensions shown in FIG. 2 was prototyped and tested. However, the portion between the ground metal plate 5 and the L-shaped elements 1 and 2 is air. The basic resonance frequency of this antenna was set to about 2 GHz. Therefore, since the wavelength λ of 2 GHz is 15 cm in free space, the dimensions are as shown in FIG. That is, the parallel portions 1a and 2a of the L-shaped elements 1 and 2 are 75 mm and the orthogonal portions 1b and 2 corresponding to 1/2 wavelength, respectively.
b is 38 mm corresponding to a quarter wavelength, and the central element 3 is 75 mm
Has become. In order to confirm the operation of this antenna, L
The return loss characteristics were measured without the shape element 2 and without the branch elements 4 and 4 '.

FIG. 3 shows the return loss frequency characteristic. A
2 is the characteristic of the antenna device of FIG. 2, B is the case without the L-shaped element 2, and C is the case without the branching elements 4 and 4 '. As is clear from this result, A is 2 GHz set to the fundamental frequency.
Multi-resonance characteristics including the vicinity are shown. A has a characteristic in which the characteristics of B and C are combined. That is, in B, it is about 0, which is indicated by Δ1.
At 84 GHz and C, it resonates at 1.0 GHz indicated by Δ2 and 2.05 GHz of the fundamental frequency indicated by Δ3, and at A, Δ1
Resonances of 8.5 GHz, Δ2 of 1.0 GHz, and Δ3 of 2.04 GHz appear. However, the resonance of Δ2 of 1.0 GHz in C is a resonance of 1 GHz, which is exactly 1/2 that of the basic resonance frequency set to 2 GHz, and this cannot be set freely, and this antenna device It is not considered the intended second resonance. From this, in the present antenna device, it is considered that the fundamental resonance frequency is 2.0 GHz and the second resonance frequency is 0.84 GHz.

The radiation patterns of the antenna device of FIG. 2 are shown in FIGS. Fig. 4 shows the measurement results at 0.84 GHz and Fig. 5 shows the measurement results at 2 GHz. First, in FIG. 5, the polarization E
Both θ and the polarized wave EΦ are weak in the X direction and tend to radiate strongly in the ± Y directions. The maximum radiation direction does not always coincide with the ± Y directions due to the influence of the ground plane, but the above tendency is clear. In addition, in the pattern of FIG.
Almost any surface is nearly omnidirectional, and polarization Eθ and polarization E
Both polarized waves of Φ radiate almost uniformly.

Consider a case where this antenna is used as a base station antenna for mobile communication installed on a side surface such as a wall. FIG. 6 is a schematic view thereof, which is a view seen from above. here,
111 is the antenna device of FIG. 1, 12 is the radiation pattern of this antenna device, 13 is buildings on both sides of the road, 14 is the road surface,
Reference numeral 15 is an area boundary to be covered by this antenna. As can be seen from this figure, a base station antenna for mobile communication installed on a side surface such as a wall does not emit strong radiation in the front direction of the antenna in order to secure a desired area. It is desirable to emit strong radiation in the lateral direction. Further, since a mobile device is mainly used as a mobile terminal, its polarized wave is not constant, and this antenna device has to transmit and receive all polarized waves.
It is necessary to have sensitivity for both the polarized waves and the polarized wave EΦ. From these facts, Fig. 5 shows that the antenna has a very good radiation pattern characteristic that meets the above conditions at 2 GHz, and Fig. 4 shows that the antenna has both polarization Eθ and polarization EΦ even at 0.84 GHz. This pattern has polarization sensitivity and is suitable for base station antennas. Further, since the propagation loss at 0.84 GHz is smaller than that at 2 GHz, it is possible to secure a desired area similar to 2 GHz even if the radiation pattern shape does not radiate strongly in the lateral direction along the road.

FIG. 7 shows the result of considering the reason why such radiation characteristics are obtained from the current distribution. A is 2 GHz, B is
This is the case of 0.84 GHz. As described above, the lengths are determined so that each side parallel to the ground plate of the present antenna has a half wavelength and each vertical side has a quarter wavelength. Therefore, at 2 GHz, the current regularly rides along the L-shaped elements 1 and 2 and the central element 3 as shown in FIG. 7A. In this case, since the elements 1a and 2a and 1b and 2b operate as opposite-phase array antennas separated from each other by ½ wavelength,
Both do not radiate in the X-axis direction, but emit strong radiation in the ± Y directions as indicated by the arrows in the figure. Furthermore, the element 1a
Since 2 and 2a radiate the polarized wave Eθ and 1b and 2b radiate the polarized wave EΦ, they have sensitivity in both polarized waves. On the other hand, at 0.84 GHz, a current flows through the L-shaped element 1, the central element 3 and the branch element 4 to resonate as shown in FIG. 7B. Therefore, the second resonance frequency can be set by the length of the branching element 4 regardless of the fundamental resonance frequency. In this case, the phases of the currents are not aligned, so
There is no particularly strong emission direction, but the current path is X
Since it is oriented in all YZ directions, it is almost omnidirectional and sensitive to both the polarized waves Eθ and EΦ.

The branching element 4 (4 ') is connected to a point within 0.3λ from the L-shaped branching element 4 on the central element 3 or an extension thereof. The reason is that it has been confirmed by experiments that the second resonance generated by the branching element becomes extremely weak beyond this range and has almost no effect. As described above, the antenna device shown in FIG. 1 has a multi-resonance characteristic, the frequencies thereof can be set individually, and has a strong radiation characteristic in the lateral direction at a high and fundamental resonance frequency, At the low second resonance frequency, it has an almost omnidirectional radiation characteristic and is sensitive to both polarizations Eθ and EΦ at both resonance frequencies. As a result, an antenna that is smaller than the conventional antenna shown in FIG. 15 and can be used for multiple systems, and is optimal as a base station antenna installed on a wall or the like can be obtained.

(Embodiment 2) FIG. 8 shows another embodiment of the invention of claim 1, which resonates at three frequencies and has good radiation characteristics as a wall-mounted base station antenna. . In FIG. 8, parts corresponding to those in FIG.
Overlapping description is omitted. In this case, the branch element is 4 (4 ')
And 7 (7 '). In this case,
The same operation is performed, but the resonance frequency can be set at three points. Similar to FIG. 1, the fundamental resonance frequency is determined, and the other resonance frequencies are determined by the first and second branch elements. These three resonance frequencies can be selected arbitrarily, but by setting the highest frequency as the fundamental resonance frequency, strong radiation characteristics in the lateral direction can be obtained at this frequency, and the low second, third resonance With respect to frequency, it has a omnidirectional radiation characteristic and is sensitive to both polarized waves Eθ and EΦ at any resonance frequency.

Therefore, the antenna shown in FIG. 8 is smaller than the conventional example and can share a system at three frequencies, which is an optimal antenna for a base station antenna installed on a wall or the like. Although the first and second branch elements are used as the branching elements in this example, the number of frequencies that can be set also increases as the number increases. Therefore, the number of branching elements is not limited to two or less, and there is no problem even if the number of branching elements is three or more depending on the required antenna resonance frequency, and the same effect as this example can be obtained.

(Embodiment 3) FIG. 9 is an embodiment of the invention of claim 5, which is a wall-mounted type base station which resonates at two frequencies and realizes strong radiation in the lateral direction at both frequencies. It has a good radiation characteristic. Also in FIG.
Portions corresponding to those in FIG. 1 are designated by the same reference numerals, and redundant description will be omitted. In this example, a bypass line 8 for phase adjustment is added in the middle of the parallel portion 1a of the L-shaped element 1.

An experiment was conducted with the same dimensions as in FIG. 75mm in length Short circuit Two parallel lines as a phase adjustment line
The element was cut off halfway and connected at a point 50 mm from the end. This return loss frequency characteristic is shown in FIG. Even with this configuration, the resonance frequency is 0.85 GHz at Δ1 and Δ3.
It becomes 2.01 GHz, and it can be seen that it resonates at two resonance frequencies. Furthermore, compared with FIG. 3A, Δ1, Δ3
Have substantially the same resonance frequency, and it can be seen that the phase adjustment line 8 hardly affects the fundamental resonance frequency.

The radiation characteristic of this antenna will be described based on the current distribution. The situation is shown in FIG. 11A shows a case where the fundamental resonance frequency is 2 GHz, and FIG. 11B shows a case where the second resonance frequency is 0.8.
This is the case of 5 GHz. The bypass line 8 has a length of 75 mm and is a parallel short line with a short-circuited terminal, so the electrical length is 1/2 at 2 GHz.
It becomes a short circuit at the end of the wavelength. This means that the phase rotates exactly 360 ° at the point 9 where the phase adjustment line 8 is connected, and even if the phase adjustment line 8 is connected, the original antenna characteristics are not affected at all. Therefore, the current distribution is as shown in FIG.
It is exactly the same as A. On the other hand, at 0.85 GHz, the bypass line 8 is short-circuited at the terminal with an electrical length of about 1/4 wavelength. This means that at the point 9 where the phase adjusting line 8 is connected, the phase turns exactly 180 °, that is, the phase is inverted. By selecting the point 9 connecting the phase adjusting line 8 as the node of the current, the current distribution as shown in FIG. 11B is obtained. This is Figure 7
Unlike B, the current phases of the L-shaped branch element 4 and the L-shaped element 1 are opposite to each other to form an antiphase array with a quarter wavelength interval,
Similar to the case of 2 GHz, strong radiation occurs in the lateral direction indicated by the arrow in the figure.

Therefore, the antenna configuration of FIG. 9 has multi-resonance characteristics, the frequencies thereof can be set individually, strong radiation characteristics in the lateral direction are obtained at both resonance frequencies, and polarization Eθ and It has sensitivity to both polarizations of polarization EΦ.
This makes it an optimal base station antenna to be installed in a small wall that can be shared by many systems. Although FIG. 9 shows the case where the number of branching elements is one, the number of branching elements is not limited to one, and there is no problem even if the number of branching elements is two or more depending on the required antenna resonance frequency as in FIG. Even in that case, the same effect as this example can be obtained.

(Embodiment 4) FIG. 12 shows an embodiment of the invention of claim 2, which resonates at two frequencies and has a good radiation characteristic as a wall-mounted base station. Corresponding parts are designated by the same reference numerals. In this case, the terminating short-circuit line 10 is connected to the end of the orthogonal portion 2b, and its outer conductor is connected to the ground metal plate 5 at the connection point 11 on the extension of the orthogonal portion 2b.
Connected to

The return loss frequency characteristic in this case is shown in FIG.
3 shows. The dimensions are almost the same as in FIG. 2, the orthogonal portion of the L-shaped element 2 is approximately 25 mm, and the coaxial terminal short-circuit line 10 having a length of 85 mm is connected to the tip thereof. Also in this case, FIG. 3A
It has almost the same characteristics as the above, and multi-resonance characteristics are obtained.
In particular, since Δ1 shows 0.82 GHz and Δ3 shows 2 GHz, the resonance frequencies are the same as those in the above-described embodiments.

The reason for this is considered as follows. The length of the terminating short-circuit line 10 is adjusted so that the guide wavelength at 2 GHz, which is the basic resonance frequency of the present antenna, is 1/2 wavelength, which is 85 mm. Therefore, at 2 GHz, 1 /
It becomes a two-wavelength termination short-circuit line, and the connection point 12 of the termination short-circuit line
Also, it looks like a short circuit. That is, at this point 12, the core wire of the coaxial 10 and the jacket are electrically short-circuited, and it is equivalent to that the orthogonal portion 2b of the L-shaped element extends to the connection point 11 between the coaxial jacket and the ground main plate. . That is, at 2 GHz, the antenna operates in the same manner as the antenna (see FIG. 3C) made up of the L-shaped elements 1 and 2 and the central element 3 of FIG. On the other hand, at 0.85 GHz, the in-tube wavelength of the coaxial line 10 becomes close to a quarter wavelength, and it becomes a quarter wavelength termination short circuit line. Therefore, at the connection point 12, the coaxial core wire and the jacket are electrically opened, and the L-shaped element 2 performs the same operation as when the L-shaped element 2 is disconnected at this point 12. That is, at 0.85 GHz, L in FIG.
It operates in the same way as an antenna made up of shaping element 1, branching element 4 and central element 3 (see FIG. 3B). Furthermore, since the phase adjusting line 8 should select the most suitable connection position depending on the frequency to which it is applied, the connection position is not limited to the L-shaped element 1 but to the central element 3 and the L-shaped element 2. You may. Further, instead of the phase adjusting line, a lumped constant phase adjusting circuit including a coil and a capacitor having the same frequency characteristic may be used.

In the example of FIG. 12, the termination short-circuited coaxial line 10 is bent toward the end of the L-shaped element 1 at the connection point 11 with the ground metal plate 5. This is desirable because the space required for the antenna is reduced (claim 4).
In this way, in the present embodiment, the two-resonance characteristic is realized by using the terminating short circuit line 10 having an appropriate length instead of using the branching element 4 (4 '). In this case, the mechanism for obtaining the two resonance characteristics is different from that of FIG. 1, but the way of riding the current is exactly the same, and the other effects are also exactly the same.

Therefore, the multi-resonance characteristic is also obtained according to FIG. 12, and the frequencies thereof can be set individually, and at the high fundamental resonance frequency, the strong radiation characteristic in the lateral direction is obtained.
At a low second resonance frequency, it has an almost omnidirectional radiation characteristic, and both frequencies are sensitive to both polarized waves Eθ and EΦ. This makes it possible to obtain an antenna that is smaller than the conventional example and is optimal as a base station antenna to be installed on a wall or the like that can be used for multiple systems.

(Embodiment 5) FIG. 14 shows an embodiment of the invention of claim 3, which resonates at three frequencies and has a good radiation characteristic as a wall-mounted base station. In this case, the branch element 4 (4 ') is added to the antenna of FIG. The branching element 4 (4 ') and the terminating short-circuit line 10 provide three resonance characteristics. Further, the phase adjusting line 8 serves as an antenna having a strong radiation characteristic in the lateral direction at all frequencies.

Therefore, this antenna also has multiple resonance frequencies, the frequencies can be set individually, the radiation characteristics are strong in the lateral direction at each resonance frequency, and both polarization Eθ and polarization EΦ are present. It is sensitive to polarized waves. As a result, the antenna is smaller than the conventional example and is optimal as a base station antenna to be installed on a wall or the like that can be shared by many systems.

Although FIG. 14 shows the case where the number of branching elements is one, the number of branching elements is not limited to one, and
As in the case of FIG. 8, two or more pieces may be provided if necessary, and in that case, the same effect as this example can be obtained. In each embodiment, a dielectric or an insulator may be interposed between the first and second L-shaped elements 1 and 2 and the ground metal plate 5. (Claim 6).

[0034]

As described above, according to the present invention, the antenna emits a strong radiation in the lateral direction, is sensitive to both vertical and horizontal polarized waves, and has a smaller size and a wider band characteristic than the conventional example. A resonant antenna device can be obtained. In particular, an optimal antenna for a small base station attached to an indoor wall can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the invention of claim 1.

2 is a perspective view showing dimensions of an experimental model of the antenna of FIG.

3 is a perspective view showing the return loss frequency characteristic of FIG. 2, where A is the characteristic as in FIG. 2, B is the case without the L-shaped element 2, and C is the case without the branch element.

FIG. 4 is a diagram showing a radiation pattern characteristic at a second resonance frequency in FIG.

FIG. 5 is a diagram showing radiation pattern characteristics at the fundamental resonance frequency of FIG.

FIG. 6 is a schematic view of the radiation pattern when the antenna of FIG. 1 is used as a wall-mounted base station antenna having a road or the like as a service area.

FIG. 7 is a perspective view showing a current distribution diagram of FIG. 1.

FIG. 8 is a perspective view showing another embodiment of the invention of claim 1;

FIG. 9 is a perspective view showing an embodiment of the invention of claim 5;

10 is a graph showing the return loss frequency characteristic of the embodiment of FIG.

11 is a perspective view showing the current distribution of the embodiment of FIG.

FIG. 12 is a perspective view showing an embodiment of the invention of claim 2;

13 is a graph showing the return loss frequency characteristic of the embodiment of FIG.

FIG. 14 is a perspective view showing an embodiment of the invention of claim 3;

FIG. 15 is a perspective view of a conventional multi-resonant antenna device.

[Explanation of symbols]

 1 1st L-shaped element 2 2nd L-shaped element 3 Central element 4, 7 L-shaped branching element 4 ', 7' Straight branching element 5 Ground metal plate 6 Coaxial feeder line 8 Phase adjustment line 9, 12 Connection point 10 Termination short circuit line 11 Connection point or grounding point 12 Radiation pattern 13 Buildings on both sides of road 14 Road surface 15 Area boundary to be covered by antenna 101 Linear whip element 102 Disk top load element 103 Multi-resonance matching circuit 104 Ground main plate 105 Feed line 107 Inverse L Element of Vertical Antenna 108 Horizontal Element A 109 Horizontal Element B 111 Antenna Device

Claims (6)

[Claims] 1. A U-shaped antenna element (the lengths of two opposite sides and an intermediate side are approximately λ / 2; λ is a wavelength of a fundamental resonance frequency of the antenna) is approximately λ / 4 that of a ground metal plate. Placed on parallel planes separated by only 2
Each end of the side is bent to the ground metal plate side at a substantially right angle, and is extended to the vicinity of the ground metal plate to form the first and second L
The first L-shaped element is connected to the core wire of the coaxial feed line led out through the small hole of the ground metal plate, and the outer conductor of the first L-shaped element is a central element. Is connected to the ground metal plate, and the end of the second L-shaped element is
A linear branch element connected to a ground metal plate and parallel to a portion of the first and second L-shaped elements parallel to the ground metal plate and having a length of λ / 2 or less, or the ground of the first and second L-shaped elements. At least one L-shaped branch element, which is parallel to the metal plate and parallel to the right-angled part, and has a parallel part having a length of approximately λ / 2 and an orthogonal part having a length of λ / 4 or less, A multi-resonant antenna, characterized in that the multi-resonant antenna is connected to a point within 0.3λ from the second L-shaped element on the central element or an extension thereof, whereby at least one resonance frequency different from the fundamental resonance frequency is set. apparatus. 2. The U-shaped antenna element (the lengths of the two sides facing each other and the middle side are approximately λ / 2; λ is the wavelength of the fundamental resonance frequency of the antenna) is approximately λ / 4 from the ground metal plate. Placed on parallel planes separated by only 2
One end of one of the sides is bent substantially at a right angle to the side of the ground metal plate, and is extended to the vicinity of the ground metal plate to form a first L-shaped element, and the end of the other side is almost the same as the ground metal plate. Bend at a right angle and have a predetermined length (within λ / 4)
To form the second L-shaped element, and the side between the two opposite sides is the central element, and the end of the first L-shaped element is connected to the core wire of the coaxial feed line led out through the small hole of the ground metal plate. Connected, the outer conductor of which is connected to the ground metal plate, the end of the second L-shaped element is connected to the core of the termination short-circuit line having a guide wavelength of λ / 2, and the outer conductor is connected to the end of the second L-shaped element. A multi-resonance antenna device, wherein the multi-resonance antenna device is connected to a point on a ground metal plate where extension lines of the parts intersect, and thereby a second resonance frequency different from the basic resonance frequency is set. 3. The method according to claim 2, wherein the first and second L-shaped elements are parallel to a portion parallel to the ground metal plate and have a length of λ /
4 or less linear branch elements, or a parallel portion having a length of approximately λ / 2 and a length of λ / 4, which are respectively parallel to a portion of the first and second L-shaped elements that is parallel to or perpendicular to the ground metal plate.
An L-shaped branch element consisting of the following orthogonal portions is connected to the central element or an extension thereof at a point within 0.3λ from the second L-shaped element, whereby a third and a third resonance frequencies different from the fundamental and second resonance frequencies are connected. The multi-resonant antenna device is characterized in that the resonance frequency is set. 4. The terminating short-circuit line according to claim 2, wherein the termination short-circuit line comprises an L-shaped coaxial line that is bent and extended in a direction along the ground metal plate at a connection point with the ground metal plate. Multi-resonant antenna device. 5. The phase adjustment line according to claim 1, wherein the first or second L-shaped element or the central element has an electric length of about ½ of a wavelength of a resonance frequency different from the fundamental resonance frequency in the middle thereof. Alternatively, a multi-resonance antenna device, to which a phase adjustment circuit is connected. 6. The dielectric or insulator according to claim 1, wherein a dielectric or an insulator is inserted between the first and second L-shaped elements and the linear (or L-shaped) branch element and the ground metal plate. A multi-resonant antenna device characterized in that