JPH0884016A - Antenna device and wireless communication device - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To efficiently mount a loop antenna and radio communication circuit in a circular housing. [Structure] Two conductor plates 22 each having a circular shape and a diameter that is sufficiently shorter than a wavelength used are arranged such that their planes face each other, and a feeding end 23 is set at a point on the outer circumference of the two conductor plates. The short-circuit conductor 24, which is configured to have a reactance that is sufficiently smaller than the circumference and has a sufficiently low reactance at the used wavelength, is connected to a position farthest from the feeding end. Since at least one of the conductor plates is cut out leaving the edge portion of the conductor plate, the display end and / or the operation end can be easily installed. [Effect] The radio communication device circuit can be mounted inside the antenna structure without lowering the antenna gain.
The size can be reduced.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is used in mobile radio communications. The present invention is suitable for use in a radio selective call receiver.
In particular, it relates to a mounting technology of a loop antenna and a radio communication device circuit.

[0002]

2. Description of the Related Art Conventionally, it has been known to use a loop antenna for a portable wireless communication device whose shape is smaller than the wavelength used. For example, the frequency used by the radio selective call receiver is several hundred MHz (300 MHz as an example).
Band, its wavelength is about 1 m), and the shape of the receiver body is several cm even in the longitudinal direction. And dozens of cm from the receiver body
It is inconvenient to carry and use a small-sized antenna. When a loop antenna is used as an antenna in such an apparatus, a practical antenna gain can be obtained with the loop passing over several% of the used wavelength (that is, several cm). Therefore, it is rational to use a loop antenna and mount it around the receiver housing.

A basic configuration of a conventional loop antenna is shown in FIG.
Will be described with reference to. FIG. 10 is a diagram showing the basic configuration of a loop antenna that has been widely known in the past. As shown in FIG. 10, the basic configuration of the loop antenna is such that a conductor wire is formed in a loop shape and one point on the loop is cut open to be a feeding end. The loop does not have to be a perfect circle,
Even if it is an ellipse or a rectangle or other shape as shown in FIG. 10, it can be used as a loop antenna as long as the conductor forms a loop.

[0004] The applicant of the present invention is Japanese Patent Application No. Hei 5-026994 (filed on Feb. 16, 1993, unpublished at the time of filing of this application), which is a loop that can form part of the housing of a wireless communication device. I applied for a patent for the invention of the antenna. In the antenna device disclosed in this prior application, two rectangular conductor plates are opposed to each other in parallel to form a loop antenna.
The present invention is that improvement.

[0005]

For example, in the case of a linear loop antenna as shown in FIG. 10, when it is installed in a housing, the shape of the antenna becomes insufficient, and the characteristics of the antenna become poor. If it is made into a convenient shape, it cannot be incorporated in the housing. When an antenna is formed by a thin conductive wire, the antenna loss is large and sufficient gain cannot be obtained, so if a plate-shaped element is used as a loop antenna to reduce the loss, this plate interferes with the display and other parts. Will not appear on the surface of the device.

The present invention has been made against such a background, and it is an object of the present invention to provide an antenna device and a wireless communication device capable of efficiently mounting a loop antenna and a wireless communication device circuit in a circular housing. To aim. An object of the present invention is to provide an antenna device which is optimal for use in a radio selective call receiver having a circular housing shape. An object of the present invention is to provide an antenna device capable of downsizing a radio selective call receiver. An object of the present invention is to provide a small loop antenna having a large antenna gain.

[0007]

The two conductor plates forming the loop antenna of the present invention are each circular, and at least one of the conductor plates is an annular conductor having a lead-out, and a feeding end. Is connected to a point on the outer circumference of the circle, and a short-circuit conductor is connected to a position distant from the feeding end.The short-circuit conductor is preferably a curved plate shape along this circle, and its width is smaller than the circumference length. Is sufficiently small and exhibits a sufficiently low reactance at the used wavelength.

The diameter of the two conductor plates is 2 to the operating wavelength.
15%, the width of the short-circuit conductor plate is 1 to 6% of the used wavelength, the part between the two conductor plates forms a part of the housing of the wireless communication device, and the wireless communication device is between the two conductor plates. It is preferable that the operation end or the display of the is attached.

That is, a first aspect of the present invention is an antenna device, which is characterized by an annular conductor,
It is provided with a conductor plate arranged substantially parallel to the annular conductor, and a short-circuit conductor electrically connecting mutually facing portions of the annular conductor and the conductor plate to each other.

It is desirable that the conductor plate has an outer shape substantially equal to the outer shape of the annular conductor.

It is desirable that the outer shapes of the annular conductor and the conductor plate are circular.

The outer shapes of the annular conductor and the conductor plate may be elliptical or an approximate shape thereof.

It is desirable to provide a feeding end for supplying a radio signal between two opposing points of an outer edge of the conductor and the conductor plate, which are separated from the short-circuit conductor.

The size of the ring conductor and the conductor plate is preferably 2% to 15% of the wavelength used.

The width of the short-circuit conductor along the ring is 1 of the used wavelength.
% To 6% is desirable.

An annular conductor plate may be provided instead of the conductor plate.

A second aspect of the present invention is a wireless communication device in which the antenna device constitutes a part of a housing.

[0018]

[Function] Circular, I set two conductor plates that are sufficiently shorter than the wavelength used so that the planes face each other, and set the feeding end at one point on the outer circumference of the two conductor plates. A short-circuit conductor having a curved plate shape along with a width sufficiently smaller than the length of the circumference and having a sufficiently low reactance at a used wavelength is connected to a position apart from the feeding end. This reduces the loss resistance of the loop antenna. Radiation efficiency is improved by these effects,
A large gain can be obtained with the same volume. Further, since the central portion is cut out leaving the edge portion of the conductor plate so as not to increase the loss, the display portion of the wireless communication device can be installed in this cutout portion. Further, since the connection with the electronic circuit of the wireless communication device is reduced by the cutout, the gain deterioration when the circuit is mounted is small.

As a result, the electronic circuit of the wireless communication device can be mounted inside the antenna structure without lowering the antenna gain, and the size can be reduced.

The annular conductor and conductor plate are preferably circular or elliptical. The shape may approximate an ellipse.

A part of the conductor plate can also be cut out. Further, the shape may be substantially the same as that of the annular conductor.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of a first embodiment device of the present invention.

The present invention is an antenna device, which is characterized by an annular conductor 21 and the annular conductor 21.
The conductor plate 22 arranged substantially parallel to the
And a short-circuit conductor 24 for electrically connecting opposite portions of the conductor plate 22 to each other. The conductor plate 22 has an outer shape that is substantially the same as the outer shape of the annular conductor 21. The outer shapes of the annular conductor 21 and the conductor plate 22 are circles.

A feeding end 23 for supplying a radio signal is provided between two opposing points on the outer edge of the annular conductor 21 and the conductor plate 22 which are separated from the short-circuit conductor 24.

The diameter of each of the annular conductor 21 and the conductor plate 22 is 2 to 15% of the used wavelength, and the width of the short-circuit conductor 24 is 1 to 6% of the used wavelength.

In the first embodiment of the present invention, the annular conductor 21 and the conductor plate 22 are arranged so that their planes face each other and are substantially parallel to each other, and the annular conductor 21 and the conductor plate 22 are short-circuited. 24, the ring-shaped conductor 21 and the conductor plate 22 are each round, and the ring-shaped conductor 21 is provided with an opening by drawing out, and one feeding end 23 is set. A short-circuit conductor 24 is connected to another position apart from 23, and the short-circuit conductor 24 has a plate shape and its width is sufficiently smaller than the length of the circumference and exhibits a sufficiently low reactance at the used wavelength. Is set.

Further, since the diameters of the annular conductor 21 and the conductor plate 22 obtain a high gain, the current distribution on the antenna element is made uniform, and the effect of increasing the sensitivity by the image of the antenna when approaching the human body is used. And this is “Small Antenns” (K.Fujimoto, A.Henderson, K.Hirasa
wa, JR James), pages 100 to 105, and is defined as 2 to 15% of the usable wavelength. Short-circuit conductor 24
The width W along the ring is limited to 1 to 6% of the used wavelength. This value is derived experimentally, and a high gain can be obtained as compared with the conventional antenna.

A portion or the whole of the casing of the wireless communication device is formed between the annular conductor 21 and the conductor plate 22, and the electric circuit of the wireless communication device is arranged between the annular conductor 21 and the conductor plate 22. , Its annular conductor 21 and conductor plate 22
The operating end of the wireless communication device or an indicator is attached to the. L × d in FIG. 1 is an annular conductor 21 that constitutes an antenna.
And the effective opening area of the conductor plate 22, and W represents the width of the short-circuit conductor 24.

Next, a mounting example of the antenna device according to the first embodiment of the present invention will be described with reference to FIG. FIG. 2 is a perspective view showing a state in which the antenna device of the first embodiment of the present invention is mounted in the housing of a wireless communication device. A circuit board 31 (a board made of an insulating material) is arranged between the annular conductor 21 and the conductor plate 22 of the loop antenna of the first embodiment of the present invention.
The switch body 32 and the display 33 are placed on the housing 3
4. The display unit of the display unit 33 is configured so that it can be viewed from the outside of the housing 34. It is generally known that the efficiency η of a loop antenna, which is generally smaller than the wavelength, is expressed by η = Rr / (Rr + Rloss) (1) where Rr is the radiation resistance of the antenna and Rloss is the electrical resistance on the loop circumference. There is. It can be seen that the efficiency η of the antenna is determined by the radiation resistance Rr and the electric resistance Rloss. Here, the radiation resistance Rr can be represented by Rr = 20 ((2π / λ) ² × S) ² (2) where S is the cross-sectional area of the loop antenna. The cross-sectional area S of the loop antenna at this time is S = d√ (a ² + (b−A / 2) ^{2 where} a and b are the side lengths of the parallel plates and d is the loop height. ) (3) can be represented. From the equation (2), the radiation resistance Rr is proportional to the square of the cross-sectional area of the loop antenna. Therefore, the radiation resistance Rr can be increased by arranging the loop antenna on the diameter as shown in FIG. 1 and connecting the loop antenna with the short-circuit conductor 24.

On the other hand, at frequencies higher than the ultra-high frequency band in which portable radios are used, current flows on the surface of the conductor due to the skin effect, so that the electric resistance Rl of the portions having the same width is used.
The oss is inversely proportional to the area W of the conductor surface as shown in the equation (4).

Rloss = (1 / W) × C × √ ((πfμ) / σ) (4) where μ is magnetic permeability, σ is conductivity, f is frequency, and C is the total length of the element. Therefore, by forming the element into a plate shape, the electric resistance Rloss decreases and the gain increases. However, in order to maximize the loop cross-sectional area, if the width of the short-circuit conductor is made thin and linear, the radiation resistance R
Although r increases, the electrical resistance Rlos due to the short-circuit conductor
Since s becomes large, the efficiency η is not improved after all.

FIG. 3 shows the matching circuit of the antenna device of the first embodiment of the present invention, and FIG. 4 shows the relationship between the short-circuit conductor width and the gain difference. FIG. 3 is a diagram showing a matching circuit used in the antenna device of the first embodiment of the present invention. FIG. 4 is a diagram showing the relationship between the short-circuit conductor width and the gain difference. The horizontal axis represents the short-circuit conductor width (λ), and the vertical axis represents the gain difference (dB). Match the antenna impedance to 50Ω using the matching circuit shown in Fig. 3,
FIG. 4 shows a change in gain in free space with reference to the peak gain of the antenna device when the width of the short-circuit element W is changed. The model in this study has the same shape as that shown in FIG. 1, and at 300 MHz, the antenna diameter is about 0.
It is 045λ. The gain is about 3 dB higher than that of the conventional antenna having the same size. Further, as compared with the antenna of the conventional example, except for the case where the electric resistance is 0.01λ or less and the short-circuit element W is wide and the loop opening area is 0.06λ or more, the opening area of the antenna according to the present technology is reduced. And the antenna gain is higher than that of the conventional antenna. From this, it can be said that the effect of the present antenna appears when the width of the short-circuit conductor is 0.01λ to 0.06λ.

Next, FIG. 5 shows the relationship between the width of the ring of the ring-shaped conductor 21 and the antenna gain difference. FIG. 5 is a diagram showing the relationship between the ring width of the ring-shaped conductor 21 and the antenna gain difference. The horizontal axis represents the width of the annular conductor (λ), that is, the width of the ring, and the vertical axis represents the antenna gain difference (dB). According to this, when the width is 0.05λ or more, there is no loss due to the hollowing out of the annular conductor 21, and the gain is almost constant.

Further, when the antenna is incorporated in the housing, the influence of a metal object built inside the antenna, especially the ground of the battery or the circuit board is large. It is effective to use the annular conductor 21 in order to avoid the influence. FIG. 6 shows an antenna gain difference when a radio device circuit having a size substantially the same as the internal size of the antenna is actually incorporated. FIG. 6 is a diagram showing the relationship between the width of the annular conductor and the antenna gain difference when the wireless device is inserted.
The horizontal axis represents the width of the annular conductor (λ), that is, the width of the ring, and the vertical axis represents the antenna gain difference (dB). When the radio circuit is not built-in, the gain is reduced by 2 dB or more due to the lead-out, but when the radio-circuit is built-in, the maximum is 0.5 when the width of the annular conductor is 0.06λ, as compared with the case without the lead-out.
The dB sensitivity can be improved, and the gain when the circuit is not built in can be almost secured.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a perspective view showing the configuration of the second embodiment of the present invention. Similarly to the annular conductor 21 for mounting a display or a switch, the conductor plate 22 adjacent to the battery 35, the ground of the circuit board, or the like is provided with a lead-out to avoid the influence of coupling. In the second embodiment of the present invention, a radio circuit having substantially the same size as the internal dimensions of the antenna is actually incorporated. The battery 35 is also built in as a part of this radio circuit, the width of the annular conductor 21 on the display surface is fixed to 3 mm, and the dimension when the conductor plate 22 adjacent to the battery 35 on the opposite side is pulled out in an annular shape is changed. FIG. 8 shows the change in gain at this time. FIG. 8 is a diagram showing the relationship between the width of the annular conductor and the antenna gain difference when two annular conductors are used. The horizontal axis represents the width of the annular conductor (λ), that is, the width of the ring, and the vertical axis represents the antenna gain difference (dB). When the cutout is large, the loss due to coupling is small, and the gain is improved by 0.7 dB at the maximum as compared with the case where the cutout is not provided.

In the first and second embodiments of the present invention, the annular conductor 21 or the conductor plate 22 has been described as a circle, but an ellipse or its approximate shape may be used. An example is shown in FIG.
Will be described with reference to. FIG. 9 is a diagram showing the shape of the annular conductor 21 or the conductor plate 22. FIG. 9A is a perfect circle. FIG. 9B is an ellipse. FIG. 9C is an ellipse. FIG. 9D is a polygon. FIG. 9 (e) is a deformation of a circle. Even if these shapes are used, the first and second embodiments of the present invention can be similarly described.

[0037]

As described above, according to the present invention,
It is possible to realize an antenna device and a wireless communication device that can efficiently mount a loop antenna and a wireless communication device circuit in a circular housing. According to the present invention, it is possible to realize an antenna device optimal for use in a radio selective call receiver having a circular housing shape. According to the present invention, it is possible to realize an antenna device capable of downsizing a radio selective calling receiver.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a state in which the antenna device of the first embodiment of the present invention is mounted.

FIG. 3 is a diagram showing a matching circuit used in the antenna device of the first embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a short-circuit conductor width and an antenna gain difference.

FIG. 5 is a diagram showing the relationship between the width of an annular conductor and the antenna gain difference.

FIG. 6 is a diagram showing a relationship between a width of an annular conductor and an antenna gain difference when a wireless device is inserted.

FIG. 7 is a perspective view showing a configuration of a second embodiment of the present invention.

FIG. 8 is a diagram showing the relationship between the width of an annular conductor and the antenna gain difference when two annular conductors are used.

FIG. 9 is a view showing the shape of an annular conductor or conductor plate.

FIG. 10 is a diagram showing a basic configuration of a conventional loop antenna.

[Explanation of symbols]

 21 annular conductor 22 conductor plate 23 feeding end 24 short-circuit conductor 31 circuit board 32 switch body 33 indicator 34 housing 35 battery

Claims (9)

[Claims] 1. A ring-shaped conductor, a conductor plate arranged substantially parallel to the ring-shaped conductor, and a short-circuit conductor electrically connecting mutually opposing portions of the ring-shaped conductor and the conductor plate. An antenna device characterized by being provided. 2. The antenna device according to claim 1, wherein the conductor plate has an outer shape substantially equal to the outer shape of the annular conductor. 3. The antenna device according to claim 2, wherein outer shapes of the annular conductor and the conductor plate are circles. 4. The antenna device according to claim 2, wherein outer shapes of the annular conductor and the conductor plate are elliptical or approximate shapes thereof. 5. The antenna device according to claim 1, wherein a feeding end for supplying a radio signal is provided between two opposing points of an outer edge portion of the conductor plate, which is away from the short-circuit conductor, of the annular conductor. 6. The antenna device according to claim 1, wherein the distance between the annular conductor and the conductor plate is 2% to 15% of the used wavelength. 7. The antenna device according to claim 1, wherein the width of the short-circuit conductor along the ring is 1% to 6% of the used wavelength. 8. The antenna device according to claim 1, further comprising an annular conductor plate in place of the conductor plate. 9. A wireless communication device in which the antenna device according to claim 1 constitutes a part of a housing.