JPS596535B2 - Satellite communication method - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a satellite communication system in which a high-gain satellite-mounted antenna can be used for communication with earth stations (including mobile stations) with a small number of calls scattered over a wide service area. be.

When satellite communications are used to communicate with ships on the ocean, communication can be made anywhere in a wide service area.

You have to make it believable. For this reason, it was necessary to widen the beam width of the satellite antenna. The disadvantage of this method is that the gain of the on-board antenna is reduced due to the widened beam width. As a means to prevent this, a method has been proposed in which the service area is divided into N zones and the mounted antenna is a multi-beam antenna with N beams corresponding to each zone. This narrows the beam width of the antenna and increases the gain. However, as the number of divisions N increases, the number of transponders mounted on the satellite increases in proportion to N, resulting in an increase in the weight of the satellite. In addition, the traffic of vessels navigating within each of the N zones is not uniform, and the communication time per vessel is also small, so no vessels are communicating within the N zones. However, it had the disadvantage that the required beams and transponders were allocated, making it not an efficient method.
In order to eliminate these drawbacks, the present invention uses M transponders, which are smaller than the number N of service area divisions, and antennas with M multibeams corresponding to each transponder, to receive calls from ship stations navigating in each zone. The purpose is to provide a satellite communication system that can increase the gain of the onboard antenna even if the number of mounted transponders is small. It is. The present invention will be explained in detail below using the drawings.

FIG. 1 shows an embodiment of the present invention, 1 (within the double line frame)
indicates the entire service area targeted by this satellite communication system, which is equally divided into N zones (N 79 in Fig. 1). As a result, ships within service area 1 are navigating in any of these zones. 2 shows an example of a ship navigating in zone 3.

4 is a communication satellite, and 5 is a coast station, through which the ship and the ground line are connected.

Communication satellite 4 is equipped with three types of antennas. 6 is an antenna for linking the coast station and the satellite, and T is an antenna that covers the entire service area 1, and is used for generating and controlling calls between the coast station 5 and the ship 2, and the like.

8 is a variable directivity antenna having the following characteristics.

(1) The beam width of the antenna (for example, 3 dB down) is
One zone (for example, 3) can be efficiently irradiated from the satellite 4.

(2) The antenna consists of a multi-beam having M beams (M<N).

(3) M beams are each independent and simultaneously N in Fig. 1.
The direction of the beam can be freely controlled so that it can correspond to any zone within the body.

In FIG. 1, only the variable directivity antenna 8 and the zone 3 are shown connected to each other in order to avoid complication of the drawing, but in reality, each of the M multibeams of the antenna 8 is shown in FIG. It is directed towards the shaded zone (
In this example, M-7). The operation of this method will be explained step by step below.

First, when the ship 2 navigating in the zone 3 wants to communicate with land, it makes a call to the coast station 5 via the access antenna 7 . In this case, the vessel 2 also informs the coast station 5 of its own navigation position. The coast station 5 directs one of the beams of the antenna 8 to the zone 3 and grants communication permission indicating the channel to be used. A link is formed in which the ship station 2 is connected to the satellite 4 via the antenna 8 and further connected to the coast station 5 via the antenna 6. FIG. 2 shows an example of a program diagram of a satellite onboard communication system for implementing this method.

The antenna numbers are the same as in FIG. 1, but the receiving antenna has a dowel and the transmitting antenna has two dowels. Furthermore, since the multi-beam antenna 8 has M beams, suffixes from 1 to M are attached to each beam. 9 is an access transponder, and 10 and 11 are a receiving section and a transmitting section of the transponder for connecting the satellite 4 and the coast station 5.

12-1, 12-2, . . . , 12-M1 and 13-1, 13-2, . . . 13-M are reception transponders corresponding to M multi-beams. An example is shown in which M different frequencies are assigned to each of the transmitter and transmitter.

Branching filters 14 and 15 combine and demultiplex M frequencies.

Multi-beam antenna 8-V, 8-2',... in Figure 2
..., 8 licks and 8-11, 8-2'', ...
..., 8-M'' can be mechanically changed to point to any one of the N zones. 1 is a program diagram showing an embodiment of the present invention.

In this case, the multi-beam antenna 8 does not need to mechanically move each beam, and is set in advance to correspond to all N service zones. Since there are only M transponders, which is less than N, NXM matrix switches 16 and 17 are inserted. In this method, the transponder can be connected to any zone by electrically controlling the NXM matrix switch. Further, some of the functions of the N×M matrix switch can be omitted to simplify the switch, and it can be connected to any zone within a certain limited range. On the other hand, access antennas have low usage and can cover the entire service area, but this is because access control signals have a small amount of information and can be sent using low-speed bits, so there is no need for high gain. do not have.

Furthermore, since it is usually easy to install a large antenna at the coast station 5, the corresponding satellite antenna may have a low gain. It is also obvious that this method can be applied to communication between ships. As explained in detail above, according to the present invention, the narrow-beam multi-beam antenna for communication mounted on the satellite can be freely directed to the zone in which the calling ship is navigating, so the satellite antenna gain is This has the advantage of being significantly improved (49 times as much as the single beam method in the example shown in FIG. 1), and of simplifying the communication equipment of ship stations and providing high-quality communication.

The system of the present invention is applicable not only to ship communications but also to mobile stations of aircraft, automobiles, or people (portable devices) or small-capacity fixed stations that are scattered over a wide service area and have a large number of low call volumes.

[Brief explanation of drawings]

Fig. 1 is a configuration example diagram showing the relationship between the coast station, satellite, and ship station of the present invention and the service area is divided; Fig. 2;
FIG. 3 is a program diagram of the communication system mounted on the satellite shown in FIG. 1... (within the double line frame) All service areas, 2...
...Ship station, 3...One of the zones, 4.
... Satellite, 5 ... Coast station, 6, 6', 6
″...-Satellite antenna for linking with the coast station, 7, T, 7″... Antenna covering the entire service area, 8, 8-V, 8-2/,...・・・・・・
8-M/, 8-1″, 8-2〃, 8-M″
...Direction variable antenna, 9...Access transponder, 10...Transponder receiving section for connecting the satellite and coast station, 11...
Transponder transmitter for connecting satellite and coast station, 12
-1 to 12-M...Transponder receiving section corresponding to M multi-beams, 13-1 to 13-M...
. . . Transponder transmitter corresponding to M multi-beams, 14 . . . Branching filter, 15.
...Blatching filter, 16, 17...
...NXM matrix switch.

Claims (1)

[Claims] 1. A multi-beam antenna with M beam patterns (M<N) necessary to efficiently irradiate the service area divided into N zones is mounted on the satellite, and the M beam directions are determined by commands. The configuration is such that each beam can be directed independently to any of the zones in the service area, and each of the M beams is allocated and linked in response to a call from a plurality of earth stations in any zone. A satellite communication system characterized by the formation of