JPH09252216A - Antenna and radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna whose antenna gain and whose beam width are varied depending on the situation so as to cope flexibly with the arrangement of base stations and terminal equipments. SOLUTION: A horn antenna 11 being a primary radiator and a reflecting mirror 12 being a reflecting means are placed on a base 10 supported turnably by a rotary joint 15. The horn antenna 11 is connected to a frequency conversion section 13, which is connected to an external transmitter-receiver or the like via a cable 14 and the rotary joint 15. The reflecting mirror 12 composed by connecting a plane 17 and a paraboloidal plane is supported by a guide 16 and fixed at an optional position.

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 base station and a terminal used for, for example, a local area radio and a wireless communication system using this antenna.

[0002]

2. Description of the Related Art There is an increasing demand for wireless communication on the premises such as a wireless LAN and a cordless telephone on the premises. At present, the antennas used for base stations and terminals in the indoor radio are omnidirectional, low-gain antennas that use a single antenna element such as a monopole, but the amount of communication information expected in the future will increase. Considering the increase in capacity and the increase in transmission speed, it is necessary to use a high frequency band having a margin in the frequency band and use a high gain antenna.

Higher gain of an antenna can be easily realized by using an array antenna in which a plurality of antenna elements are arranged or an aperture antenna such as a reflecting mirror. However, the wireless environment in the premises is determined by the positions of the base station and the terminal. Multiple antennas are necessary, considering that there are various changes due to.

For example, as shown in FIG. 11, when the base station 1 is directly above the terminal 2 as shown in the relationship between the base station 1 and the terminal 2, the distance between the base station 1 and the terminal 2 is short. The gain of the terminal antenna may be low. However, when the line forms a certain angle of view and the propagation distance is long like the relationship between the base station 1 and the terminal 3, it is necessary to increase the antenna gain in order to secure the communication line. It is desired to switch the antenna gain.

Considering the line maintenance, it can be said that any situation can be dealt with as long as the antenna gain is high. However, if the antenna gain is increased more than necessary, the beam width becomes narrow and the pointing of the antenna beam becomes difficult. It becomes difficult and the coverage area becomes smaller than necessary. In particular, since the base station may communicate with a plurality of terminals, it is preferable that the coverage area of the beam is large, and the gain of the base station antenna is as wide as possible at the minimum level required.

In order to meet the above demands, the conventional system using a low gain antenna using one antenna element, a high gain array antenna, an aperture antenna, etc., has a communication environment considering the arrangement of base stations and terminals. It was difficult to flexibly respond to changes.

[0007]

As described above, in the conventional indoor radio antenna, the antenna gain and the beam width are fixed, and it is flexible to the change of the communication environment due to the change of the arrangement of the base station and the terminal. It was difficult to deal with.

The present invention has been made to solve the above problems, and provides an antenna whose antenna gain and beam width can be changed according to the situation in order to flexibly cope with the arrangement of base stations and terminals. With the goal.

An object of the present invention is to provide an antenna capable of coping with both secure securing of a communication line, ease of pointing of an antenna beam and expansion of a coverage area.

It is another object of the present invention to provide an antenna which can more easily adapt the communication environment by changing the antenna gain and beam width.

It is another object of the present invention to provide an antenna which can realize the above object with a compact and simple structure.

A further object of the present invention is to provide a wireless communication system which has both a stable communication line and easy system construction.

[0013]

In order to solve such a problem, an antenna according to claim 1 has a primary radiator, a first surface forming a first beam width, and a second beam width. A second surface to be formed, the reflection means changing the positional relationship between these surfaces and the primary radiator to change the reflection surface.

The antenna system of the primary radiator does not matter. Besides the horn antenna, other planar antennas such as microstrip antennas and spiral antennas, and linear antennas such as helical antennas and dipole antennas can also be used.

The first beam width and the second beam width mean that the beam widths are different from each other. Specifically, for example, by making the first surface and the second surface have different shapes,
The beam widths may be different from each other. More specifically, for example, there are a combination of a flat surface and a cylindrical parabolic surface, a combination of a flat surface and a parabolic surface, and a combination of both cylindrical parabolic surfaces or parabolic surfaces having different beam widths. Alternatively, a surface that diverges the beam, such as a cylindrical parabola or the outer surface of the parabola, may be used. Further, the present invention includes a mirror surface that gradually changes from a flat surface to a parabolic surface, a part of the reflecting mirror that is a spherical surface, or a part that changes the irradiation area of the reflecting mirror.

The positional relationship between the first surface and the second surface and the primary radiator can be changed, for example, by moving the reflecting means, and can also be changed by moving or rotating the primary radiator. .

Changing the reflection surface by changing the positional relationship between the first surface and the second surface allows switching of one of the first surface and the second surface so as to act as the reflection surface. It also includes stepwise changing the ratio of the reflective surface that acts as a reflective surface and the ratio of the reflective surface that acts as a reflective surface.

The antenna according to the first aspect is premised on that the beam width and the maximum gain in the beam direction have a correlation. That is, it is assumed that the maximum gain in the beam direction is large when the beam width is narrow, and the maximum gain in the beam direction is small when the beam width is wide. And
When the propagation distance is long, the influence of the surface having a large maximum gain in the beam direction (the surface having a narrow beam width) on the reflecting surface with respect to the primary radiator is increased. As a result, the communication line can be surely secured. When the propagation distance is short, the influence of the surface having a wide beam width (the surface having a small maximum gain in the beam direction) on the reflecting surface with respect to the primary radiator is increased. Thereby, pointing of the antenna beam can be facilitated. Alternatively, the coverage area can be expanded. Moreover, in the antenna according to claim 1,
The beam direction can also be changed by changing the reflecting surface, but this change in beam direction can be associated with the change in beam width. Can be done more easily. For example, in a communication environment in which the propagation distance is short when the beam is directed straight up, and the propagation distance is long as the beam direction approaches horizontal, the beam width is wide and horizontal when the beam direction is straight up. The beam width becomes narrower as it gets closer to. This makes it possible to construct an optimum system that matches the communication environment, simply by matching the beam directions.

An antenna according to claim 2 has a primary radiator and a rotatable reflector having a front surface forming a first beam width and a back surface forming a second beam width. And a reflecting means for rotating and causing one of the front surface and the back surface to act as a reflecting surface for the primary radiator.

The definition of the primary radiator, the beam width, etc. of claim 2 is the same as that of claim 1 described above,
The difference is that reflectors having different beam widths on the front and back are used and the reflectors are configured to rotate.

The antenna described in claim 2 has the same effect as that of the invention described in claim 1, but the beam width is changed by further rotating the reflection plate, so that the switching portion can be made more compact. It can be configured and can be easily configured.

A rotating mechanism for rotating the antenna in a horizontal plane can be added to the antenna according to the first or second aspect. As a result, the direction of radio waves transmitted and received by the antenna can be rotated in the horizontal plane. A rotary joint capable of transmitting a signal can be used as the rotating shaft of the rotating mechanism.

In the antenna according to claim 1 or 2, frequency conversion means can be added to the primary radiator. Thereby, signal transmission in the transmission line connecting the primary radiator and the transceiver can be performed at a lower frequency. The frequency converting means can be integrated with the rotating mechanism.

In the antenna according to the first or second aspect, a light emitting means for emitting light toward the reflecting means can be added to the primary radiator. As a result, light is also emitted in the same direction as the radio wave, and the antenna can be aligned visually.

A system according to claim 3 is a wireless communication system for communicating between a base station and a plurality of terminals via a wireless transmission path, wherein a beam width is provided near the base station and the terminal. , A wide antenna is used, and an antenna with a narrow beam width is used at a place distant from the base station and the terminal. For example, a terminal near the base station may have an antenna with a wide beam width, and a terminal far from the base station may have an antenna with a narrow beam width. The present invention can be similarly applied to the antenna of the base station.

As an antenna used in such a system, it is preferable to use the antenna described in claims 1 and 2, but the invention is not necessarily limited to this. For example, an antenna having a different beam width is used as a base station. You may comprise so that it may exchange according to the distance with a terminal.

The system according to the third aspect of the present invention has both the stable securing of the communication line and the ease of system construction.

[0028]

FIG. 1 is an external view showing an example of an antenna to which the present invention is applied. FIG. 2 is a front view of FIG.

In these figures, 10 is a pedestal.
The pedestal 10 has, for example, a disk shape, the center of which is rotatably supported by a rotary joint 15, and can be manually or automatically rotated in a horizontal plane, that is, around the Z axis. On the pedestal 10, a horn antenna 11 as a primary radiator, a reflecting mirror 12 as a reflecting means, and other means are mounted.

The horn antenna 11 includes a frequency converter 13
The frequency converter 13 is connected to the external transmitter / receiver or the like via the cable 14 and the rotary joint 15 capable of transmitting signals.

The reflecting mirror 12 is supported by a guide 16 and can be manually or automatically moved in the direction of arrow A, and can be fixed at any position. Further, the reflecting mirror 12 is configured by connecting the flat surface 17 and the parabolic surface 18. The flat surface 17 has a wide beam width but a small maximum gain in the beam direction, and the parabolic surface 18 has a narrow beam width but a large maximum gain in the beam direction.

FIG. 3 is a diagram showing the configuration of the frequency conversion unit 13. As shown in the figure, transmission and reception of the signal from the horn antenna 11 is separated by the demultiplexer 31. Here, instead of the demultiplexer 31, a circulator, a switch, or the like may be used. The received signal is a low noise amplifier (LNA) 32,
The frequency converter 33 and the combiner / distributor (a circulator or a switch may be used instead) 34 are sequentially connected, and a signal is transmitted to an external transmitter / receiver or the like. The transmission signal is transmitted from an external transmitter / receiver or the like through the divider / combiner 34 to the frequency converter 3
5 and is transmitted from the horn antenna 11 via the high output amplifier 36 and the demultiplexer 31. The operation of the frequency conversion unit 13 is to convert the transmission / reception signal amplification and signal transmission with an external device into a low frequency band in which transmission loss is reduced. In particular, since the frequency band used in the wireless LAN is 1.9 GHz or higher, disposing such a frequency conversion unit 13 in the immediate vicinity of the horn antenna 11 causes a great loss in the transmission line. There is an effect that can be reduced. Further, since the rotary joint 15 is passed through after being converted to a low frequency band, there is an effect that the loss in the rotary joint 15 can be made very small. Next, the operation of this antenna will be described. The same operation is performed only when the radio wave propagation directions are reversed during transmission and reception, so the transmission will be described below.

The radiated radio wave from the horn antenna 11 serving as a primary radiator is reflected by the reflecting mirror 12 and propagates in a predetermined direction. The radiated radio wave from the horn antenna 11 is in which part of the reflecting mirror 12 (the plane 17 or the parabola). The pattern, gain, etc. of the reflected radio wave changes depending on whether the surface 18) is hit centrally.

For example, as shown in FIG. 4, when the portion of the radiated radio wave from the horn antenna 11 as the primary radiator having a high intensity is almost on the plane 17, the radio wave reflected by the reflecting mirror 12 is primary by the plane 17. It appears to be emitted from point 40, which is the mirror image of the radiator. That is, in this case, the beam width is wide, but the maximum gain in the beam direction is small.

Further, by moving the reflecting mirror 12 in parallel, as shown in FIG. 5, the portion of the radiated radio wave from the horn antenna 11 as the primary radiator having a high intensity is almost the portion of the parabolic surface 18, and the horn antenna 11 is the same. When it is at the focus position, the radio wave reflected by the reflecting mirror 12 is reflected on the parabolic surface 1
It is focused by 8 and becomes a parallel wave and radiates away. When the light is reflected by the parabolic surface 18, the gain in the radiation direction is higher than that in the case of the flat surface 17, and thus the beam width is narrowed.

In the case of the parabolic surface 18 and the flat surface 17, the radiation direction of radio waves changes. Now, FIG.
The coordinate system is set as shown in, so that the radiation direction of the plane 17 coincides with the Z direction. The radiation pattern at this time has a low gain and a wide beam width, as indicated by 61 in FIG. 6B. By moving the reflecting mirror 12 in the direction of the arrow, the beam direction changes as in the radiation pattern 62, the gain increases, and the beam width decreases. Finally, when the reflecting surface becomes the parabolic surface 18, it is possible to realize directivity in which the beam direction is most deviated, the gain is the highest, and the beam width is the smallest, as in the radiation pattern 63.

Therefore, in this example to which the present invention is applied, by moving the reflecting mirror 12 in parallel, the beam direction can be changed in six directions and the gain can be changed. In addition, in the antenna of this example, by providing the rotary joint 15, since the rotary joint 15 can be rotated in the horizontal plane about the central axis, the beam direction can also be changed in the horizontal rotation angle direction, and in the 6 directions. The beam direction can be freely adjusted by combining with the beam direction scanning of.

Therefore, in the antenna of this example, the reflector 1
The beam width and the maximum gain can be changed by a simple method of changing the position of 2. In other words, one antenna can realize different directivities with different radiation gains and beam widths, and there is no need to prepare multiple antennas for different line conditions, communication environments, and services.
As a result, the antenna can be efficiently used, which leads to cost reduction in consideration of the entire system.

By moving the reflecting mirror 12 so that a part of the reflecting mirror 12 is a flat surface 17 and a part thereof is a parabolic surface 18, the gain is low and the beam is wide when the angle θ is zero, as shown in FIG. From the state, the gain can be increased and the beam can be made thinner as the angle θ increases. Also, the maximum radiation direction changes simultaneously. Such a property has a very high utility value considering the environment of the indoor radio.

FIG. 7 shows an example of a local wireless communication system in which a terminal has an antenna according to the present invention. As shown in the figure, the base station antenna 70 is arranged on the ceiling,
A plurality of terminals 71 to 73 are arranged on the floor. Terminal 7
1 to 73 each have an antenna according to the present invention, for example, the antenna 74 shown in FIG.

Here, the antenna 74 of the terminal 71 arranged directly below the antenna 70 of the base station has a short propagation distance, so that the antenna gain may be low. At this time, by reflecting the radio wave on the flat surface 17 of the reflecting mirror 12,
A directivity 75 having a wide beam width and a low gain can be formed with the beam direction directly above. At this time, since the beam width is widened, the line is not cut off due to a pointing error caused by a positional shift or movement of the base station or terminal.

As the positions of the terminals move away from the terminals 72 and 73 and the antenna 70 of the base station, the propagation distance becomes longer, and the direction of the antenna 70 of the base station as seen from the terminals approaches horizontally from directly above. come. In such a case,
By tilting the beam direction by moving the reflecting mirror 12 and gradually changing the radio wave reflecting surface to the parabolic surface 18.
The gain can be increased, and a good communication environment can be maintained regardless of the location of the terminal. As described above, the beam deviation of the antenna of this example, the change in gain, the characteristics required by the terminal in the indoor radio, can be realized with a single antenna simple configuration, as a terminal antenna of the indoor radio The effect is great.

Further, in the antenna of this example, the beam direction can be freely changed in the horizontal plane by providing the rotating mechanism including the pedestal 10 and the rotary joint 15 and horizontally rotating the antenna arrangement surface. . Therefore, within a circle of a certain radius centered on this antenna, the line can be connected regardless of where the partner's radio station is. Further, by using the rotary joint 15 capable of transmitting a signal as the rotating shaft of the rotating mechanism, the antenna can be rotated and the transceiver system can be installed in a fixed state.

Further, by connecting the frequency converter 13 to the horn antenna 11 as a primary radiator, it becomes possible to exchange signals with an external transmitter / receiver in a low frequency band with respect to the RF frequency. . For this reason, it is possible to use a transmission line and a rotary joint for rotary drive, which have low loss and high accuracy at low frequencies, and various devices provided in these propagation paths can be inexpensive and small. .

The following structure can be considered as the structure of the reflecting mirror.

(1) Connection of a flat surface and a cylindrical parabolic surface The parabolic portion of the reflecting mirror is assumed to be linear in the XZ plane with respect to its vertical direction (Y axis). In this case, the beam direction and the gain in the elevation angle direction of the antenna change with the parallel movement of the reflecting mirror, but the beam width remains wide because the reflecting mirror is straight in the rotation angle direction. Therefore, even if the gain becomes high, the positional accuracy when the antenna is rotated in the horizontal plane is good, and the rotary drive mechanism can be easily made.

(2) A plane and a parabolic surface are connected to each other. The parabolic portion of the reflecting mirror becomes a parabolic surface whose focal point is the phase center of the primary radiator after translation. In this case, the gain of the reflection field by the parabolic surface after the parallel movement of the reflecting mirror can be maximized.

(3) Mirror surface that gradually changes from a plane to a parabolic surface In the case of (2) above, the joint between the plane and the parabolic surface becomes a discontinuous mirror surface with a step. In this case, there is a possibility that directivity may be deteriorated such as side lobe rise due to scattering due to steps. Therefore, it is possible to prevent deterioration of directivity by gradually changing the mirror surface.

(4) By combining a spherical surface that partially makes the reflecting mirror a spherical surface and a parabolic surface, a spherical surface that can reduce the change in gain during driving is combined to provide variations in characteristics such as gain during beam scanning. be able to. In the indoor wireless communication, it is possible to realize the optimum beam scanning characteristics in consideration of the complicated shape in the building.

(5) Changing the irradiation area of the reflecting mirror By changing the size of the reflecting mirror in addition to the mirror surface shape,
Variations in gain and beam changes during beam scanning can be provided.

(6) Making the initial mirror surface other than a flat surface In the above (1) to (5), the mirror surface shape used when the beam is radiated right above is not a flat surface but a partial parabolic surface. It is also possible to use a mirror surface and increase the gain in the case of irradiating the beam directly above.

In addition to this, a combination of a plurality of shapes of mirror surfaces is conceivable, and the same effect as the effect shown in the above-described example can be obtained.

In the above example, the explanation has been made on the premise that the reflecting mirror moves in parallel, but rotation or the like may be performed in addition to this. In this case, it becomes possible to change only the beam direction with the same gain. For example, as shown in FIG. 8, the front surface and the back surface of the reflecting mirror 80 may have different mirror surface shapes. For example, the front surface 81 is a plane and the back surface 82 is a parabolic surface,
The beam direction and the gain can be changed by turning over the reflecting mirror by rotating it. In this case, the area occupied by the reflecting mirror 80 in the entire antenna can be reduced, so that the entire antenna can be made compact.

Further, by arranging the light emitting element 91 in the vicinity of the primary radiator 11 as shown in FIG. 9 or by providing the light emitting element 101 integrated with the primary radiator 11 as shown in FIG. Light is emitted from the primary radiator 11, reflected by the reflecting mirror 12, and emitted. Reflector 12
On the other hand, since the radio wave and the light are reflected in the same manner, it is possible to visually confirm the portion where the visible light reaches, and the direction thereof coincides with the maximum beam direction of the radio wave. Light emitting element 91,
By generating visible light by using 101, the invisible beam direction can be confirmed, so that the alignment between wireless devices can be performed easily and in a short time.

The configuration of the frequency converter 13 is not limited to that shown in FIG. For example, a transmitter / receiver and the like may be integrated within the frequency conversion unit.

[0056]

As described in detail above, according to the present invention,
By changing the positional relationship between the first and second surfaces and the primary radiator to change the reflecting surface, it is possible to change the antenna gain and the beam width depending on the situation with one antenna. That is, it is possible to deal with both securement of a communication line and ease of pointing of an antenna beam or expansion of a coverage area with one antenna. For example, it becomes possible to switch the beam according to the indoor radio environment such as the positional relationship between the base station and the terminal with one antenna, and it is not necessary to change the antenna according to the communication environment.
It is effective for cost reduction.

Further, by adaptively associating the change in the beam direction with the change in the beam width, it is possible to easily adapt to the communication environment by changing the antenna gain and the beam width.

Further, since the reflectors having different beam widths on the front and back sides are used and the reflectors are rotated, the switching portion can be made more compact and the construction can be simplified.

Further, by using the antenna having such a structure in, for example, a local radio communication system, it becomes possible to secure both a stable communication line and easy system construction.

[Brief description of drawings]

FIG. 1 is an external view showing an example of an antenna to which the present invention is applied.

FIG. 2 is a front view of FIG.

FIG. 3 is a block diagram showing a configuration of a frequency conversion unit shown in FIG.

FIG. 4 is a diagram showing an operation of the antenna of FIG.

5 is a diagram showing an operation of the antenna of FIG.

6 is a diagram for explaining a beam direction and a gain of the antenna of FIG.

FIG. 7 is a diagram showing an example in which the present invention is applied to a local wireless communication system.

FIG. 8 is a front view showing another example of the antenna to which the present invention is applied.

FIG. 9 is a front view showing another example of the antenna to which the present invention is applied.

FIG. 10 is a front view showing another example of the antenna to which the present invention is applied.

FIG. 11 is a diagram showing a general example of a local area radio communication system.

[Explanation of symbols]

 10 Pedestal 11 Horn Antenna (Primary Radiator) 12 Reflector 13 Frequency Converter 14 Cable 15 Rotary Joint 16 Guide 17 Plane 18 Parabolic Surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Kayano Hiroyuki Kayano 1 Komu, Toshiba-cho, Kawasaki-shi, Kanagawa Kanagawa Prefectural Research & Development Center (72) Inventor Akihiro Tsujimura Ko, Kawasaki-shi, Kanagawa Muko Toshiba Town No. 1 Inside the Toshiba Research and Development Center, a stock company (72) Inventor Koji Iino One stock company located at 3-1, Asahigaoka, Hino City, Tokyo Inside the Toshiba Hino Factory (72) Inventor Takashi Amano Asahigaoka, Hino City, Tokyo Toshiba Corporation Hino Factory, a stock company at 3 chome 1

Claims (3)

[Claims] 1. A primary radiator, a first surface forming a first beam width, and a second surface forming a second beam width, the surfaces of the first radiator and the first radiator. An antenna comprising: a reflection unit that changes a positional relationship between the reflection surfaces to change a reflection surface. 2. A primary radiator and a rotatable reflector having a front surface forming a first beam width and a rear surface forming a second beam width, and the front or back surface is rotated by rotating the reflector. An antenna, comprising: one of the two surfaces serving as a reflecting surface for the primary radiator. 3. A wireless communication system for performing communication between a base station and a plurality of terminals via a wireless transmission path, wherein an antenna having a wide beam width is used near the base station and the terminal, A radio communication system, characterized in that an antenna having a narrow beam width is used in a place where the base station and the terminal are distant from each other.