JP2000278193A - Diversity antenna device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a diversity antenna device which improves multipath resistance. SOLUTION: Three omnidirectional antenna elements A to C are arranged in an equilateral triangle at a half wavelength interval d (d = λ / 2). Excitation signals from these antenna elements A to C are split into two by splitters 11 to 13, respectively, and combined by combiners 21 to 23.
Lead to. The combiners 21 to 23 combine signals from the antenna elements A and B, A and C, and B and C, respectively, in opposite phases. This has a lobe along the sides of the equilateral triangle 3
One reception beam is formed, and diversity reception is performed using these reception beams.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a diversity antenna device that can be suitably used for a (bile Satellite Broadcast) system or the like.

[0002]

2. Description of the Related Art With the recent increase in demand for communication, the field of mobile communication has been remarkably developed. In recent years, not only a conventional system completed only with ground-side facilities, but also a broadcasting system for mobile objects using artificial satellites (hereinafter, referred to as satellites) has been put into practical use.

[0003] In a mobile communication environment, multipaths usually exist. In particular, in the metropolitan area, a large number of multipath waves are generated from a building or the like, and arrive at a receiver antenna with a time difference. It is well known that if this becomes severe, communication quality will be significantly impaired. To improve multipath resistance, cellular systems, PHS (Personal Handyphone System),
There is a demand throughout the mobile communication field such as MSB. In addition, CDMA (Code Divisio), which has attracted attention in recent years,
n Multiple Access) technology is known to be highly resistant to multipath, but cannot suppress multipath that arrives at an interval shorter than the processing time of the processor. Is still weak.
Under such circumstances, various efforts have been made to improve the multipath resistance, and research and development particularly on the receiving antenna portion have been actively conducted.

FIG. 8 shows a configuration of a conventional antenna device used in a multipath environment. This antenna device
As shown in FIGS. 8A and 8B, four antenna elements A
~ D are arranged in a regular square, and two reflectors R1, R2
By extending the beam in four directions as shown in FIG. 8C, directivity in all directions is obtained. By switching each of the antenna elements A to D in this configuration, directional diversity can be realized, and multipath resistance can be improved.

FIG. 9 shows another configuration of a conventional antenna device. In this antenna device, two antenna elements A and B are arranged at an interval d = λ / 2 (λ is a wavelength), and power is supplied to each antenna element A and B in the same phase and the opposite phase, so that a dotted line and a solid line in FIG. To obtain the orthogonal directivity indicated by.
By switching these directivities, directivity diversity can be realized, and multipath resistance can be improved.

[0006]

However, in the configurations shown in FIGS. 8 and 9, the center of the directivity of each antenna element is located at the same point. For this reason, even if the directivity is switched, the correlation among a plurality of multipath signals is still strong, and it cannot be said that the diversity effect is weak.

[0007] The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a diversity antenna device with improved multipath resistance.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides m antennas arranged at the vertices of a polygon having m sides, and m antennas which are adjacent to each other. A combined receiving beam forming means for forming an antenna pair with each other, combining receiving beams of two antennas belonging to each antenna pair to form m combined receiving beams having different receiving positions, and the m combining beams; M reception signals corresponding to each of the reception beams are provided, quality evaluation is performed on these reception signals, and the highest quality reception output is determined based on the m reception signals based on the result of the quality evaluation. Output means for generating and outputting.

As a criterion for quality evaluation in the output means, the reception level of each received signal may be used, or the S / N ratio or C / N ratio of each received signal may be used.

The output means may be configured to generate and output the reception output by weighting and combining the received signals based on the result of the quality evaluation, or to output the result of the quality evaluation. A received signal having the highest quality may be selected based on the signal, and the received signal may be output as a received output.

When the wavelength of the radio signal to be received is λ, m omnidirectional antennas are provided at the vertices of a regular m-sided polygon having a side length corresponding to a natural number times (λ / 2). M splitters that respectively split the element signals from the m omnidirectional antennas into two to generate 2m branch signals in the combined reception beam forming means, and 2m splitters , Two branch signals based on element signals transmitted from the omnidirectional antennas adjacent to each other are provided, respectively, and these provided branch signals are combined in opposite phases to perform the combined reception. M beam combiners for forming a beam may be provided.

In this way, m combined reception beams having phase centers or reception positions at different points, pointing in mutually different directions, and jointly covering all directions are formed. . Therefore, the arriving radio signal is received by these combined reception beams at different places and with different directivities.

These received signals are weighted or combined or selected by the output means, so that the highest quality received signal output can be obtained.

That is, since each received signal is received at a different location, it is possible to obtain a spatial diversity effect on the incoming radio signal. Further, since each received signal is received with different directivity, it is possible to obtain a directional diversity effect on an incoming radio signal.

For this reason, the two effects can be combined to further enhance the selectivity of the signal, and the anti-multipath performance can be further improved.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) FIG. 1 shows a configuration of an MSB system in which a diversity antenna device according to an embodiment of the present invention is used. In FIG. 1, a radio wave transmitted from a broadcast satellite 10 is received by an automobile 30 and a plurality of retransmission stations 201 to 20n existing on the ground. Each retransmission station 20
1 to 20n perform processing such as amplification and waveform shaping on a received radio wave, re-emit this to a predetermined area, and develop a service area on the ground.

The car 30 can receive radio waves from the broadcast satellite 10 in a place where the view to the broadcast satellite 10 is good. On the other hand, in a shadowed place, for example, the retransmission station 20
n to receive the retransmitted radio wave and perform communication with the broadcasting satellite 10. At that time, many multipaths occur on the ground side, and in order to cope with this, the diversity antenna device 40 according to the present invention is mounted on the upper surface of the body of the automobile 30.

FIG. 2 shows the configuration of the diversity antenna device according to this embodiment. In this antenna device, three omnidirectional antenna elements A to C are arranged at a half wavelength interval (d = λ
/ 2) are arranged in an equilateral triangle, and the signals from the respective elements A to C are branched into two by the distributors 11 to 13, respectively.
Lead to 23.

The combiner 21 receives the signals from the antenna elements A and B, inverts the signal from the element B, synthesizes the inverted signal with the signal not inverted by the element A, and gives a synthesized output ab.
Here, signal inversion is indicated by (-1), and signal inversion is indicated by (1). The combiner 22 receives the signals from the antenna elements A and C, inverts the signal from the element C, combines the inverted signal with the signal of the element A that is not inverted, and provides a combined output ac. Synthesizer 2
3 receives the signals from the antenna elements B and C, inverts the signal from the element C and combines the inverted signal with the signal that is not inverted from the element B, and gives a combined output bc. Each composite output ab, a
c and bc are given to the switching / combining unit 3 and the control unit 4.

The control section 4 receives the given combined outputs ab,
The switching / combining unit 3 is controlled based on the signal levels of ac and bc, and the combined outputs ab and a are controlled by known diversity control.
c and bc are switched and each composite output a
b, ac, and bc are further combined in any combination to obtain a diversity output.

Next, the operation of the above configuration will be described.
FIG. 3 shows the directional characteristics of dipole antennas installed at half-wavelength intervals (d = λ / 2). When the antenna elements A and B are fed in opposite phases, the overall directivity is formed along the element arrangement direction (x-axis) as shown by the solid line in the figure. At this time, the y-axis direction is null. On the other hand, when the antenna elements A and B are fed in phase with each other,
The directivity as a whole is formed along the direction (y-axis) perpendicular to the arrangement of the elements, as indicated by the dotted line in the figure. At this time, the x-axis direction becomes null.

By taking the directional characteristics shown in FIG. 3 into consideration, it can be seen that the directional characteristics shown in FIG. 4 are formed in the diversity antenna apparatus shown in FIG. That is, the directivity pattern of each of the combined outputs ab, ac, and bc has a figure-eight shape along the arrangement direction of the corresponding antenna elements.
With these three patterns, it is possible to cover the horizontal plane in all directions. The phase center (null point) of each directivity pattern is located at a different point.

When attention is paid to the pattern ab by the antenna elements A and B, for example, the gain in the direction of the antenna element C is 0, that is, the antenna beam by the pattern ab does not face the antenna element C direction. As a result, unnecessary current due to mutual coupling is not excited in the antenna element C, and good reception characteristics can be obtained. Of course, the same effect is obtained for the elements B and C.

Further, each directional pattern ab, ac, b
Since the phase centers of c are located at different points, a spatial diversity effect can also be obtained by switching and outputting these patterns. That is, in this embodiment, by switching or combining and outputting the directivity patterns ab, ac, and bc, it is possible to simultaneously obtain the directivity diversity effect and the space diversity effect for multipath. Therefore, even in a poor environment where a large number of multipaths arrive at short time intervals, such as in a metropolitan area, it is possible to enhance the signal selectivity and suppress the adverse effects of the multipaths.

As described above, in the present embodiment, the three omnidirectional antenna elements A to C are separated from each other by a half wavelength interval d (d = λ
/ 2) to arrange in an equilateral triangle. These antenna elements A
To C respectively by distributors 11 to 13
It branches and leads to combiners 21-23. The combiners 21 to 23 combine signals from the antenna elements A and B, A and C, and B and C, respectively, in opposite phases. Thus, three reception beams having lobes are formed along the sides of the equilateral triangle, and diversity reception is performed using these reception beams.

With this configuration, it is possible to have a phase center, that is, a receiving point at different places, form a plurality of receiving beams having different directivities, and cover all directions with these receiving beams. By performing diversity reception based on the received signals received by these receive beams, directivity diversity and spatial diversity can be performed simultaneously, and the effects of both combine to further improve signal selectivity. As a result, the multipath resistance can be further improved.

In the above embodiment, the directivity is not obtained by combining the excitation signals from the plurality of omni-directional antennas, instead of installing the plurality of directional antennas at different locations to perform space diversity. To form a receiving beam. By doing so, it is possible to always cover the space with uniform directivity regardless of the movement of the automobile 3.

(Second Embodiment) Next, a second embodiment of the present invention will be described. FIG. 6 shows the configuration of the diversity antenna device according to the present embodiment. 2 are denoted by the same reference numerals, and only different parts will be described here.

In the antenna apparatus shown in FIG. 6, four omnidirectional antenna elements A to D are arranged in a square at a half wavelength interval (d = λ / 2), and signals from these elements A to D are respectively transmitted. The reception beam shown in FIG. 7 is formed by performing two branches and performing inversion synthesis.

[0030] Even in this case, it is possible to form reception beams having different directivities which have phase centers at different places and cover all directions. Diversity reception of signals obtained from these reception beams can provide directivity and space diversity effects, and can achieve higher multipath suppression effects.

The present invention is not limited to the above embodiment. For example, in each of the above embodiments, the arrangement interval of the antenna elements is set to a half wavelength, but may be arranged at one wavelength interval d = λ. For example, when omnidirectional antenna elements provided at one wavelength interval are fed in phase or in opposite phase, a crowbar-like pattern shown in FIG. 5 is obtained. The same effect as described above can be obtained by forming a plurality of reception beams having such a shape and performing diversity reception. However, since this pattern develops lobes in the orthogonal direction, it is necessary to consider how to install the antenna to avoid unnecessary induced current.

Further, the above discussion is further extended, and in general, d
= N · λ / 2 (n is a natural number), the same effect as described above can be obtained. However, in the case of an antenna device mounted and used on a moving body or the like, the size becomes a problem, so that it is preferable to install the antenna device at half wavelength intervals.

Further, in each of the above embodiments, the diversity control is performed based on a signal given from each antenna element in a radio frequency (RF) state. However, the present invention is not limited to this, and the baseband signal after demodulation and detection is used. May be used to perform diversity control. In each of the above embodiments, the diversity control is performed based on the signal level. However, the present invention is not limited to this.
Diversity control may be performed based on the N ratio or the C / N ratio.

Although the above embodiments have been described with the MSB system in mind, the idea of the present invention can be applied to other wireless communication fields such as CDMA systems.

In addition, various modifications can be made without departing from the gist of the present invention.

[0036]

As described in detail above, the present invention forms a plurality of receive beams having different phase centers and directivities, and performs diversity reception based on signals received by these receive beams. Therefore, it is possible to provide a diversity antenna device with improved multipath resistance.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a configuration of an MSB system in which a diversity antenna device according to an embodiment of the present invention is used.

FIG. 2 is a block diagram showing a configuration of the diversity antenna device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing the directional characteristics of dipole antennas installed at half-wavelength intervals (d = λ / 2).

FIG. 4 is a composite output ab, ac, b in the configuration of FIG.
The figure which shows the directivity pattern of c.

FIG. 5 is a diagram showing the directional characteristics of dipole antennas installed at one wavelength interval (d = λ).

FIG. 6 is a block diagram showing a configuration of a diversity antenna device according to a second embodiment of the present invention.

FIG. 7 shows a composite output ab, ac, c in the configuration of FIG.
The figure which shows the directivity pattern of d and bd.

FIG. 8 is a diagram showing a configuration of a conventional antenna device used in a multipath environment.

FIG. 9 is a diagram showing another configuration of a conventional antenna device used in a multipath environment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Broadcasting satellites 201-20n ... Retransmission station 30 ... Car 40 ... Diversity antenna device A-D ... Antenna element 11-14 ... Distributor 21-23, 51-54 ... Synthesizer 3 ... Switching / synthesis part 4 ... Control part

Claims (6)

[Claims] 1. An antenna having m antennas arranged at vertices of a polygon having m sides, and antennas adjacent to each other forming an antenna pair, and two antennas belonging to each antenna pair Combined reception beam forming means for combining respective reception beams of the antennas to form m combined reception beams having different reception positions; and m reception signals corresponding to each of the m combination reception beams. And output means for performing quality evaluation on these received signals, generating and outputting the highest quality reception output based on the m received signals based on the result of the quality evaluation. Diversity antenna device. 2. The diversity antenna device according to claim 1, wherein the output unit generates the reception output by weighting and combining the received signals based on the result of the quality evaluation. . 3. The method according to claim 1, wherein the output unit selects a received signal having the highest quality among the given m received signals based on a result of the quality evaluation and outputs the selected signal as the received output. The diversity antenna device according to claim 1, wherein: 4. The diversity antenna device according to claim 1, wherein the output unit performs quality evaluation on the m received signals using a reception level of each signal as a criterion for evaluation. 5. The signal processing apparatus according to claim 1, wherein the output unit is configured to output an S / N ratio for each signal.
2. The diversity antenna device according to claim 1, wherein quality evaluation is performed on the m received signals using a ratio or a C / N ratio as an evaluation criterion. 3. 6. The m antennas each have a vertex of a regular m-sided polygon having a side length corresponding to a natural number times (λ / 2), where λ is a wavelength of a radio signal to be received. M omni-directional antennas to be arranged, wherein the combined reception beam forming means splits element signals from the m omni-directional antennas into two to generate 2m branch signals. A splitter is provided with two branch signals based on element signals transmitted from the omnidirectional antennas adjacent to each other, among these 2m branch signals, and these given branch signals are inverted from each other. The diversity antenna apparatus according to claim 1, further comprising: m combiners that form the combined reception beam by combining the phases.