JPS63227130A - Mobile radio communication system - Google Patents

Abstract

PURPOSE:To improve the transmission quality by setting equally to each other the rotational directions of circularly polarized waves of a circularly polarized wave upward beam antenna loaded on a moving body, and a circularly polarized wave downward beam antenna connected to a ground fixed station. CONSTITUTION:A building 5 is built against a road 1 on which a vehicle 3 runs and a man 13 walks. At a prescribed place separated from the building 5, a ground installation antenna 2 is supported by a support 2a, and also, a ground installation antenna 12 is attached to the upper prescribed position, as well, of the building 5. Moreover, the vehicle 3 is loaded with a mobile antenna 4, and the man 13 carries a portable antenna 14. The antennas 2, 12 radiates a radio wave as a circularly polarized wave in the prescribed rotational direction, and the radiation directivity is set downward. The antennas 4, 14 receive only a circularly polarized wave of the same rotational direction as the circularly polarized wave radiated from the antennas 2, 12, and the radiation directivity is set upward. In such a way, the transmission quality can be maintained high.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a mobile radio communication system, and more specifically, the present invention relates to a mobile radio communication system, and more specifically, the present invention relates to a mobile radio communication system. The present invention relates to a mobile radio communication system for exchanging data between.

<Prior art> Mobile radio communication systems have been employed to exchange data between taxis, cargo collection and delivery vehicles, etc. (hereinafter collectively referred to as mobile objects) and ground fixed stations. By giving instructions and status reports from the moving body, efficient operation or reaching the appropriate destination can be achieved.

Specifically, a monopole antenna with a simple configuration is mounted on the mobile object, and a ground-mounted antenna connected to a ground fixed station is attached to a building, tower, elevated road, etc. A system configuration that transmits and receives radio waves is adopted. By setting the radiation directivity of the ground-mounted antenna so that it can radiate radio waves of a predetermined level or higher over a reasonably wide range, the mobile object can receive radio waves from the ground fixed station while moving within the range. It is possible to transmit necessary data or to transmit necessary data from a mobile object.

Furthermore, car phones and the like are also included in the above mobile radio communication system, but car phones need to be able to send and receive data over a much wider range than the system that sends and receives data to and from taxis and freight collection vehicles. They differ only in certain points, and are basically homogeneous systems.

<Problems to be Solved by the Invention> In the mobile radio communication system described above, when wireless communication is performed between the ground-mounted antenna and the monopole antenna, the transmission quality deteriorates due to fading due to multipath, etc. There is a problem in that there is a high possibility that data transmission will occur, and there is no guarantee that reliable data transmission can be performed within a predetermined range centered on the ground-mounted antenna.

To explain in more detail, the driving conditions of other vehicles near the ground-mounted antenna, the arrangement of buildings, etc. change significantly over time or from one ground-mounted antenna to another, and the radiation from the ground-mounted antenna changes significantly. In addition to being directly received by the monopole antenna, the signal is also received by the monopole antenna after being reflected by buildings, roads, other vehicles, etc. Since the signals have different amplitudes and phases, they are summarily or differentially superimposed, resulting in a signal with an intensity distribution that is significantly different from the intensity distribution of the transmitted signal from the ground-mounted antenna. This results in a signal whose phase is shifted from that of the transmitted signal from the installed antenna, and there is no guarantee that the transmitted data can be accurately restored on the receiving side.

Specifically, as shown in FIG.
A monopole antenna (24) is mounted on the roof of the vehicle (23). The above-mentioned ground-mounted antenna (22) has a somewhat high directivity, as shown by B in the figure, and is attached to the pillar' (22a) so as to transmit a signal in a nearly vertically downward direction.

Therefore, the signal from the ground antenna (22) is
A part of it is reflected by the roof of another vehicle (23) or the road surface, as shown in C and D in the figure, and the monopole antenna (
24), the other part is directly guided to the monoball antenna (24) as shown in E in the figure, and the rest is guided only by the building (25) as shown in F and G in the figure. It is reflected or sequentially reflected by the building (25) and the road shoulder (21a) and guided to the monopole antenna (24).

Furthermore, in addition to the reflected waves described above, scattered waves also exist.

As a result, even if a single signal transmitted from the same ground-based antenna (22) is received by one monopole antenna (24), it will pass through each path to the monopole antenna (24) as described above. (24) interfere with each other to form a standing wave, or the signals passing through each of the above paths are summarily or differentially superimposed on each other, so that the movement of the vehicle (23) As a result, the signal reception level fluctuates sharply (see FIG. 4), degrading data transmission quality.

In addition, the signals guided to the monopole antenna (24) through each route are determined by the propagation path length and reception timing (the time required from when the signal is transmitted until it is received by the monopole antenna (24)). Since they are different from each other, the phase relationship for each received signal will be different.
The overall received signal will differ significantly from the transmitted signal, degrading the data transmission quality.

The above problem is not limited to mobile radio communication systems that cover a relatively wide communication area such as car telephones.
Even in a mobile radio communication system that covers a relatively narrow communication area with a radius of several hundred meters, the problem becomes noticeable in areas where buildings, elevated tracks, roads, etc. are densely packed, such as in the center of a city.

<Object of the invention> This invention was made in view of the above problems,
It is an object of the present invention to provide a mobile radio communication system that can improve transmission quality by eliminating the effects of multipath, fading, etc. when exchanging data in a relatively narrow communication area.

Means for Solving the Problems> In order to achieve the above object, the mobile radio communication system of the present invention is a circularly polarized upward beam antenna mounted on a mobile body, and a ground fixed station. The antenna connected to is a circularly polarized downward beam antenna, and the rotation directions of the circularly polarized waves of both antennas are set to be equal to each other.

In the mobile radio communication system described above, when data is exchanged between a mobile body and a ground fixed station, the antenna mounted on the mobile body is a circularly polarized upward beam antenna, 2.Since the antenna connected to the fixed station is a circularly polarized downward beam antenna, the antenna mounted on a mobile object receives reflections from buildings, road surfaces, road shoulders, the roofs of other vehicles, etc. in the horizontal direction, Or, it will not receive the signal guided from below, but will only receive the signal guided from above. The signal transmitted from the antenna connected to the ground fixed station is circularly polarized, and the signal that can be received by the antenna mounted on the mobile object is circularly polarized in the same direction of rotation. As a result of being reflected, it does not receive the signal guided from above, and receives only the signal guided from above without being reflected at all.

Therefore, only the signals transmitted and directly guided from the antenna connected to the terrestrial fixed station are received by the antenna mounted on the mobile object, and the transmission quality can be maintained high.

Conversely, when transmitting a signal from an antenna mounted on a mobile object, only the signal transmitted from the antenna mounted on the mobile object and guided directly from below is received by the antenna connected to the ground fixed station, and the transmission quality is improved. can be maintained high.

<Example> Hereinafter, embodiments will be described in detail with reference to the accompanying drawings showing examples.

FIG. 1 is a diagram schematically showing a mobile radio communication system of the present invention, and shows an example of its application in an urban area.

A building (5
) is being built. A ground-mounted antenna (2) is supported by a pillar (2a) at a predetermined location away from the building (5), and a ground-mounted antenna (12) is also supported at a predetermined location on the top of any of the buildings (5).
) is installed. Furthermore, the vehicle (3) is equipped with an on-vehicle antenna (4) on the roof, and a human (13)
is carrying a mobile antenna (14).

To explain in more detail, the above ground-mounted antenna (2)
(12) is connected to a ground fixed station (not shown), and emits radio waves modulated corresponding to the data supplied by the ground fixed station as circularly polarized waves in a predetermined rotational direction. , the radiation directivity is set so that the radiation electric field strength is strongest in the downward direction. Further, the vehicle-mounted antenna (4) and the mobile antenna (14) are connected to a receiver (not shown), and are circularly polarized in the same direction as the circularly polarized waves radiated from the ground-mounted antennas (2) and (12). It receives only polarized waves, and the radiation directivity is set so that the radiated electric field strength is strongest in the upward direction.

The data transmission operation by the above mobile radio communication system is as follows.

The radio waves radiated from the ground-mounted antenna (2) are directly guided to the vehicle-mounted antenna (4) mounted on the vehicle (3) that is running almost directly below the ground-mounted antenna (2) (Fig. (See middle A) as well as buildings (
5) is reflected and then guided (see B in the figure)
At the same time, radio waves radiated from other ground-mounted antennas (12) are guided as they are (see C in the figure).

However, as shown by B in the figure, the building (5)
The radio waves that are guided after being reflected only once have a fairly strong electric field strength and are guided from the near true. However, the direction of rotation of the circularly polarized waves is reversed due to the reflection, so it is difficult to use the vehicle antenna ( ) is never received by. Although not particularly shown, as the number of reflections from the building (5) increases, not only the electric field strength decreases, but also the direction of incidence on the vehicle antenna (4) becomes closer to the horizontal direction. Actual car antenna (4)
The received signal strength is significantly reduced to a negligible level. Furthermore, as shown by C in the figure, the radio waves directly guided from the other ground-mounted antennas (12) are incident in a fairly horizontal direction because the spacing between the ground-mounted antennas is not set too small. The electric field strength decreases considerably as the angle increases, so even if the direction of rotation of the circularly polarized waves is the same, the signal strength actually received by the on-vehicle antenna (4) decreases significantly and can be ignored. It will reach the level of

Therefore, the only radio waves that are received with sufficient signal strength are those that are radiated from directly above the building (5) and have not been reflected at all by the building (5), as shown by A in the figure, and are multipathed. , it is possible to perform data transmission in a state where the influence of fading is almost completely eliminated, and to maintain high transmission quality.

In addition, a mobile antenna (14) carried by a person (13)
), as in the case of the in-vehicle antenna (4), only radio waves are emitted from directly above the vehicle and are not reflected at all by the building (5).
Data transmission can be performed in a state where the effects of multipath and fading are almost completely eliminated, and transmission quality can be maintained at a high level.

FIG. 2 shows a state in which the communication area of the ground-mounted antenna is set to cover an intersection.

In the drawing, a vehicle (
3) shows the state of entering an intersection and the state of turning right at the intersection, but since the ground-mounted antenna emits circularly polarized radio waves almost downward,
The on-vehicle antenna (4) mounted on the vehicle (3) traveling straight in any direction can receive only direct waves. However, although the reception level changes due to the difference in distance, the change is not too large and any vehicle-mounted antenna (4) can receive direct waves at a sufficient level.

Also, vehicles turning right at the intersection (3), vehicle exit turning left)
In either case, only direct waves can be received at a sufficient level.

Note that the present invention is not limited to the above-mentioned embodiments, and can be applied to, for example, a vehicle-mounted antenna (4) and a mobile antenna (1).
4) can be used as the transmitting side and the ground-mounted antenna (12) can be used as the receiving side, and both can be used for transmitting and receiving Ak, within the scope of not changing the gist of this invention. It is possible to make various design changes.

<Effects of the Invention> As described above, the present invention uses a circularly polarized downward beam antenna as an antenna connected to a fixed ground station, and uses a circularly polarized downward beam antenna as an antenna mounted on a mobile object in the same rotational direction. Therefore, only direct waves can be transmitted and received when both antennas are relatively close to each other, and the unique effect is that transmission quality can be maintained at a high level.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an outline of the mobile radio communication system of the present invention, Fig. 2 is a diagram showing a state in which a vehicle is traveling through an intersection, Fig. 3 is a schematic diagram showing a conventional example, and Fig. 4 is a diagram according to a conventional example. FIG. 3 is a diagram showing received signal strength distribution. (2) (12)...ground-mounted antenna, (3)...
Vehicle, (4)...In-vehicle antenna, (13)...Human, (14)...Mobile antenna Patent applicant Sumitomo Electric Industries, Ltd. 1 Representative Patent attorney Hiroshi Kamei Katsu 1-. ,,,
, ,, I l (and 3 others)′″゛-

Claims (1)

[Claims] 1. Data transmission between the mobile unit and the fixed terrestrial station A mobile radio communication system that sends and receives data. In systems, antennas mounted on moving objects circularly polarized upward beam antenna is an antenna connected to a fixed terrestrial station. circularly polarized downward beam antenna , and the rotation direction of the circularly polarized waves of both antennas is are set equal to each other. mobile radio communication system.