JP2003298340A - Antenna for wireless apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna which is non-directional, small-sized, light weight and highly reliable. <P>SOLUTION: A shielding plate to shield a transmit receive circuit (RF circuit) of a wireless communication apparatus is used as a ground plate, and a radiation plate is arranged with a fixed distance kept with a short-circuit conductor. A reverse F antenna which uses the shielding plate as the ground plate is constituted. A diversity antenna is constituted by arranging a plurality of reverse F antennas toward different directions, and an almost non-directional antenna is realized by a directional characteristic obtained by synthesizing directional characteristics of two antenna elements. <P>COPYRIGHT: (C)2004,JPO

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 a wireless communication device such as a wireless LAN, and more particularly to a wireless device antenna suitable for use as a diversity antenna capable of improving directivity. is there.

[0002]

2. Description of the Related Art An antenna used for a wireless LAN access point or the like is generally formed so as to project outside from a case containing a transmission / reception circuit such as an RF section. FIG. 6 shows a disassembled photograph of such an access point, in which two antennas for diversity are attached to a case and have an outer shape protruding in a horn shape outside the case. Since such an antenna protrudes from the case, mounting is restricted and a directivity problem may occur.

In addition, it is desirable that the directional characteristics be substantially the same in all directions in order to satisfactorily perform transmission / reception regardless of the position of a terminal device that transmits / receives signals. Further, it is desired that the device is small and lightweight so that the grounding place is not restricted. Moreover, in order to maintain the characteristics of the antenna, it must be able to maintain a certain shape.

[0004]

SUMMARY OF THE INVENTION The present invention provides a diversity antenna having good directivity in all directions, and an antenna that can be housed in the case of a wireless communication device. As a result, it is possible to maintain the communication quality regardless of the direction of the terminal device and to provide a radio device antenna having a good assembly quality.

[0005]

SUMMARY OF THE INVENTION The present invention uses the inverted F antenna having a shield case of a transmission / reception circuit as a ground plate, and further combines a plurality of (two) inverted F antennas having different directions to solve the above problems. Is the solution.

That is, in a radio device antenna connected to a transmission / reception circuit of a communication device, a plurality of radiation plates arranged at predetermined intervals are provided outside a shield case which covers the transmission / reception circuit formed on a printed wiring board. It is characterized in that a part of the end face of each radiation plate is short-circuited to the shield case to form an inverted F antenna using the shield case as a ground plate. The shield case and the radiation plate can be integrally formed from a single metal plate.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The RF part of a wireless communication device is usually shielded from the surroundings by a metal plate so that it is not affected by the surroundings and does not affect the surroundings. Since this shield plate is connected to the ground potential, it serves as the ground plate for the inverted F antenna. Since the ground plate and the radiation plate are partially short-circuited in the inverted F antenna, the antenna is integrally formed by cutting and raising a part of the metal plate that constitutes the shield plate.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of the present invention. 1 shows an example of an access point for a 2.4 GHz band wireless LAN.

In this example, the shield case covering the RF part is a metal plate having a thickness of 0.3 mm, a length of 69.3 mm, a width of 44.5 mm and a height of 2.6.
It is formed with a size of mm. Antenna is 22.5mm x 1
The 8.0 mm radiating plates 13A and 13B are arranged at a 6 mm distance from the shield plate. The radiation electrode 13A and the radiation electrode 13B are connected to the shield plate 10 at a position opposite to each other with a metal plate having a width of 5.0 mm and short-circuited. The power supply conductors 17A and 17B extend toward the shield plate at a position 11 mm from the ends, and are connected to the transmission / reception circuit when assembled.

The device in which the antenna is integrally formed on the shield plate as described above is housed in a resin case and its characteristics are measured. The results are shown in FIGS. 2 to 5.

As shown in FIG. 2 (B), the orientation of the antenna when the apparatus equipped with the antenna according to the present invention is installed horizontally and the horizontally polarized radio wave is emitted from each direction of the horizontal plane. The characteristics are shown in (A-1) to (A-3). The two antennas A and B are arranged as shown in FIG. 6B, and the reception level at each position is shown in the counterclockwise direction with the front surface of the antenna B side as 0 °.

In this example, the antenna A has null points near 60 ° and 240 ° as shown in FIG. 2A-1, and the antenna B has a null point as shown in FIG. 2A-2. Is 160 ° and 34
There is a null point near 0 °. If only each antenna is used, the reception level will drop significantly, but Fig. 2 (A-3)
As shown in, when combined, the decrease in reception level can be suppressed to a low level.

FIG. 3 shows the characteristics when vertical polarization is used in the same horizontal arrangement as in FIG. In this case also, the two antennas cover each other to ensure a certain reception level.

FIG. 4 shows a case where the apparatus is installed vertically and horizontal polarization is used. In this case, the antenna A side is shown as 0 °, and in this example, the reception level greatly decreases at the position of 180 °. This is a state in which the radio waves reach from the back side of the shield plate, so it is inevitable that the level will drop because of an obstacle. When actually used, since it is often installed on the wall surface, reception of radio waves from the back side can be avoided and no trouble occurs.

FIG. 5 shows a case where the apparatus is vertically installed and has a vertically polarized wave. As with the examples shown in FIGS. 2 and 3, an antenna which can be said to have substantially omnidirectionality can be obtained. It is shown that. The use of the antenna according to the present invention eliminates null points due to the diversity method, eliminates the difference in the reach of radio waves depending on the location (direction), expands the range in which stable communication can be maintained, and is greatly improved over the conventional technology. It was

[0016]

According to the present invention, regardless of the installation direction,
A diversity antenna having omnidirectionality in all directions can be obtained, and it becomes easy to maintain a stable communication state in a wireless communication device. Further, since the antenna element can be downsized and housed in the case, the device can be downsized and lightened, and the installation place can be freely selected. Furthermore, since the antenna element can be formed integrally with the shield plate by using a metal plate, the assembly quality can be easily maintained, and a highly reliable communication device can be obtained.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of directional characteristics of an antenna according to the present invention.

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

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

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

[Figure 6] Disassembled photograph of wireless communication device

[Explanation of symbols]

10: Shield case 13: Radiant plate 15: Short-circuit conductor 17: Feeding conductor

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5J021 AA02 AA09 AB06 CA06 EA04                       FA32 GA07 HA05 HA06 HA10                 5J045 AA05 AA21 AB05 DA08 HA06                       MA04 NA01                 5J047 AA04 AA12 AB10 AB13 FD01                 5K011 AA06 AA15 JA01

Claims (4)

[Claims] 1. A radio device antenna connected to a transmission / reception circuit of a communication device, comprising: a radiation plate arranged at a predetermined interval outside a shield case for covering the transmission / reception circuit formed on a printed wiring board, An antenna for a wireless device, wherein a part of an end face of the radiation plate is short-circuited to a shield case to form an inverted F antenna using the shield case as a ground plate. 2. A radio device antenna connected to a transmission / reception circuit of a communication device, comprising: a plurality of radiation plates arranged at predetermined intervals outside a shield case which covers the transmission / reception circuit formed on a printed wiring board. An antenna for a wireless device, characterized in that a part of an end face of each radiation plate is short-circuited to a shield case to form an inverted F antenna using the shield case as a ground plate. 3. The antenna for a wireless device according to claim 1, wherein the radiation plate is formed integrally with the shield case. 4. The antenna for a wireless device according to claim 2, wherein a plurality of radiation plates are short-circuited in different directions to combine a plurality of antennas having different directivities.