JP2001223517A - Frequency sharing antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-frequency sharing antenna which is small-sized, of a small area and of a planar shape. SOLUTION: A monopole antenna 12 is erected on a bottom plate 11, a square conductor plate 13 is mounted on the antenna 12 to be made a planar antenna resonating in a frequency f1, the conductor plate 13 faces the plate 11 at the opposite sides, and a square loop conductor piece 31 is connected to the conductor plate 13 with a short circuit conductor 32 so as to be resonated by the conductor piece 31 and the antenna 12 in a frequency f2 that is lower than the frequency f1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, as an antenna for a mobile station mounted on a ceiling or the like for measures against a blind spot in mobile communications. In particular, the antenna resonates at two frequencies while having a planar shape as a whole. That is, the present invention relates to a frequency sharing antenna shared by two frequency bands.

[0002]

2. Description of the Related Art Conventionally, a planar antenna is mounted on a ceiling or the like and used as an antenna for a mobile station. That is, as shown in FIG. 7, the monopole antenna 12 is erected at the center of the rectangular ground plate 11, and the rectangular conductor plate 13 is mounted on the protruding end of the monopole antenna 12 in parallel with the ground plate 11 at the center thereof, An intermediate portion of the monopole antenna 12 is short-circuited to the ground plane 11 by a conductor 14 for impedance matching, and a feeder 15 is attached to the ground plane 11 on the side opposite to the monopole antenna 12. The shape and size of the base plate 11 are sufficiently large with respect to the wavelength used.

By mounting the conductor plate 13 in this manner, a capacitance component is loaded, and the length of the monopole antenna 12 can be made shorter than a quarter of the used wavelength. , The overall height can be reduced, and a planar antenna can be obtained. For example, the base plate 11 is mounted on the ceiling side of the room, so that the protrusion from the ceiling is not noticeable. In addition, by adopting such a low-profile shape, the impedance is reduced to several Ω.
, Preferably two impedance matching conductors 14,
By providing a so-called trap circuit, the 5
The impedance is matched to 0Ω.

When the planar antenna is used in the 2.0 GHz band, the lengths W ₁ and W ₂ of each side of the rectangular conductor plate 13 are set.
Is 0.11λ (λ is a wavelength of 2.0 GHz), and the height H ₁ of the monopole antenna 12 is 0.10λ, thereby realizing an omnidirectional antenna.

[0005]

Conventionally, two frequency bands are used in order to cope with blind spots of mobile radio. In this case, as an antenna in this case, as shown in FIG. And the planar antenna 22 for the second frequency band shown in FIG.
Are commonly used. Such an antenna device has a drawback that the installation space becomes large.

[0006]

According to the present invention, a conventional planar antenna which resonates at a first frequency is substantially parallel to a flat conductor on the side opposite to the ground plane, and a part thereof is short-circuited. The conductor piece is provided so that resonance occurs even at a second frequency lower than the first frequency.

[0007]

FIG. 1 shows an embodiment of the present invention.
Parts corresponding to those in FIG. 7 are denoted by the same reference numerals, and redundant description is omitted. That is, in the planar antenna resonating at the first frequency shown in FIG. 7, on the side opposite to the ground plane 11, a rectangular loop conductor piece as a conductor piece 31 parallel to the ground plane 11 partially short-circuits with the conductor plate 13. Provided. In this example, the square loop conductor pieces 31 have a substantially square shape, and are rotated by about 45 degrees with respect to the square conductor plate 13 about the center line of the monopole antenna 12 so as to face each other. I have. In addition, the midpoint of one side of the loop conductor piece 31 is connected to one corner portion of the square conductor plate 13 by a connection conductor 32 and the loop conductor piece 31 is supported by the conductor plate 13.

According to this configuration, the monopole antenna 1
2 and the conductor plate 13 to operate as an antenna at the resonance frequency f _{1 as} in the prior art, and the resonance frequency f _{2 determined} by the monopole antenna 12 and the loop conductor piece 31.
Operate as an antenna, that is, operate as a two-frequency resonance antenna. In this case, the loop conductor piece 31 is
It is necessary to reduce these couplings since they do not operate as a two-frequency resonance antenna when they are coupled with the antenna 3. From this point, the conductor piece 31 may be a flat conductor, but is preferably a loop conductor, and is more preferable in terms of reducing the height of the entire antenna, that is, the length of the monopole antenna 12 in the extending direction. In addition, the conductor plate 31 and the conductor plate 13 are not opposed to each other from the point
Although it is better to shift in the direction parallel to 1, the conductor piece 31 is a rectangular loop conductor piece and is opposed to the conductor plate 13 as shown in FIG. 1 from the viewpoint of reducing the antenna area as a whole. In this case, the angle should be shifted from the viewpoint of reducing the coupling.

A specific example will be described below. The conductor plate 13 is placed on each side W
₁= W_Two0.11λ₁, Higher than the ground plane 11 of the conductor plate 13
H₁0.10λ₁(Λ₁Is the wavelength of 2.0 GHz)
And the outer side W of the loop conductor piece 31_Three= W_FiveIs 0.17λ
_Two, Inside side W_Four0.15λ _Two, W₆Is 0.12λ_Two,
Height H of conductor piece 31 above ground plate 11_Two0.15λ
_Two(Λ_TwoIs a wavelength of 1.5 GHz). In this case,
Turn loss frequency characteristics are as shown in Fig. 2.
-25.04 dB at 1.492 GHz, 2.127
-19.88 dB at GHz and almost 1.5 GHz and 2.0
A resonance phenomenon occurred at GHz. In other words, this antenna has two laps
It has been confirmed that the antenna operates as a wave sharing antenna. Also
FIG. 3 shows directional characteristics in a horizontal plane at 1.492 GHz.
FIG. 4 shows the directional characteristics in the vertical plane at 2.127 GHz.
Fig. 5 shows the directional characteristics in the horizontal plane, and Fig. 6 shows the directional characteristics in the vertical plane.
Shown respectively. From these, 1.492 GHz, 2.1
The directional characteristics in the horizontal plane at 27 GHz are almost omnidirectional.
Yes, the directional characteristic in the vertical plane is a figure-eight characteristic, but its half-value width
Were both broad.

The height H ₁ of the conductor plate 13 is fixed,
When the loop conductor piece 31 is brought close to the conductor plate 13, 1.5 G
Although the resonance characteristic around 1 Hz becomes sharp, the resonance characteristic around 2.0 GHz becomes weaker. On the contrary, when the conductor piece 31 is separated from the conductor plate 13, the resonance characteristic around 1.5 GHz becomes weaker.
The resonance characteristics around 0 GHz become stronger. When the area of the conductor piece 31 is increased, the lower resonance frequency is reduced, and when the area of the conductor plate 13 is reduced, the higher resonance frequency is increased. The connection point between the conductor piece 31 and the conductor plate 13 is the conductor plate 1
Any three points may be used. A dielectric plate 33 having a small high-frequency loss may be interposed between the conductor plate 13 and the conductor piece 31, and the conductor piece 31 may be supported on the conductor plate 13 by the dielectric plate 33.

[0011]

As described above, according to the present invention, 2
A planar antenna that can be used for one frequency band can be configured to have a small area, that is, a small size.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, wherein A is a plan view and B is a front view.

FIG. 2 is a diagram showing return loss characteristics of the embodiment of the present invention.

FIG. 3 is a diagram showing a directional characteristic in a horizontal plane in a 1.5 GHz band of the embodiment.

FIG. 4 is a diagram showing a directional characteristic in a vertical plane in a 1.5 GHz band of the embodiment.

FIG. 5 is a diagram showing a directional characteristic in a horizontal plane in the 2.0 GHz band of the embodiment.

FIG. 6 is a diagram showing a directional characteristic in a vertical plane in a 2.0 GHz band of the embodiment.

FIG. 7 shows a conventional single-resonance planar antenna, where A is a plan view and B is a front view.

FIG. 8 is a perspective view showing a dual-frequency antenna using a conventional planar antenna.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01Q 21/30 H01Q 21/30 (72) Inventor Yoshio Ebine 2-1-1 Toranomon, Minato-ku, Tokyo N・ Within TTI Mobile Communication Network Co., Ltd. 5J046 AA04 AA12 AB06 AB13 TA04

Claims (4)

[Claims] At the tip of a monopole antenna with a ground plate,
A flat conductor mounted in parallel with the ground plane, an impedance matching conductor for short-circuiting a substantially middle portion of the monopole antenna and the ground plane is provided, and an antenna device resonating at a first frequency; Wherein a conductor piece substantially parallel to the flat conductor and partially short-circuited therewith is provided so that resonance occurs even at a second frequency lower than the first frequency. antenna. 2. The frequency sharing antenna according to claim 1, wherein said conductor piece is a loop-shaped conductor piece. 3. The planar conductor has a rectangular shape, the conductor piece is a rectangular loop-shaped conductor piece, and the rectangular loop-shaped conductor piece and the rectangular planar conductor have an angle around the monopole antenna. 3. The frequency sharing antenna according to claim 2, wherein the antennas are substantially 45 degrees apart from each other and face each other. 4. The frequency sharing antenna according to claim 1, wherein a dielectric plate is interposed between said conductor piece and said conductor plate.