JPS6317254B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a communication system that can increase the service area by antenna beams when performing satellite communication using a multi-beam antenna.

To simplify the explanation, we will consider a geostationary satellite equipped with a multi-beam antenna, and assume that the beam radiated from the multi-beam antenna is approximately circular. FIG. 1 shows one of the beams radiated from a multi-beam antenna in terms of viewing angle (in degrees) as seen from the satellite. In the figure, 1 indicates the center direction of this beam, and 3 indicates the shape of the beam with a visual radius of θ degrees. This is an equal level line that shows the antenna gain we need now (assuming GodB). In other words, the range 3 can be said to be an area that can be irradiated with a gain G _p or more. On the other hand, the attitude of a satellite changes due to disturbances such as mechanical imbalance of the satellite itself and solar radiation pressure, and the beam direction of the antenna changes accordingly. Assuming that the attitude of the satellite, that is, the beam direction of the antenna, varies by δ degrees in all directions with respect to the beam center direction 1, the irradiation area that is always G _p will be a narrow range as shown in 2.

Next, consider the case where a service area as shown by 4 in FIG. 2 is irradiated with multiple beams. 1 in the diagram
a, 2a, 3a are respectively in the center direction of beam a,
The irradiation area is shown when taking into account the attitude variation of the satellite, and the irradiation area when the attitude variation of the satellite is set to 0. 1b, 2b, 3b indicate the same in beam b. In the figure, there are two beams, a and b, which are arranged so that the regions 2a and 2b are in contact with each other. When the distance between the beams is narrow like this, it is necessary to change the frequency of each beam to cause interference between the beams. Here, beam a
Suppose f _a and beam b use frequency f _b . Then, when considering transmission from a satellite, the area constantly irradiated by f _a in the service area 4 is the area surrounded by 2a f _b , the area constantly irradiated is the area surrounded by 2b, and the diagonal line in 5 The surrounded area becomes a non-irradiation area. One way to reduce such non-irradiated areas is to use an antenna that places another beam c between beams a and b in the case shown in Figure 2. In this case, the number of beams increases, making the on-board antenna system complex, and the frequency needs to be increased.

The purpose of the present invention is to provide a multi-beam communication system that minimizes non-irradiated areas, and enables earth stations belonging to some of the areas in 5 to transmit or receive multiple frequencies, and to The system is equipped with a multi-beam antenna, and unlike satellites whose attitude changes over time, each beam can illuminate a single service area with a different frequency. In a multi-beam communication method, an area that is outside the area irradiated by each beam with a predetermined gain or higher and that is constantly irradiated by one of the beams despite temporal fluctuations in the irradiation beam due to changes in the attitude of the satellite. The earth station installed in the satellite has a transmitter/receiver that can transmit and receive multiple frequencies, and uses a multi-beam communication method in which the frequency is switched to a stronger beam frequency in response to fluctuations in the irradiation beam due to changes in the satellite's attitude. .

Examples will be described below with reference to the drawings.

FIG. 3 is a drawing explaining an embodiment of the present invention. If we further classify the non-irradiated area shown in 5 in Figure 2, as shown in 6, the area is always irradiated with either frequency f _a or f _b even when the attitude of the satellite changes. and the other area 5' as indicated by diagonal lines. Region 6 exists because the relationship between the two beams remains constant despite changes in the attitude of the satellite.
5' is an area where there is a time when neither frequency f _a nor f _b is irradiated due to attitude fluctuations of the satellite. Here, as explained earlier, beam a has f _a and beam b
Suppose we use the frequency of f _b for . Then, at the earth station within the area surrounded by 2a of service area 4,
If you have a device that can transmit and receive the f _a frequency band, you can always communicate with the satellite, and similarly, the geostation in the area surrounded by 2b has a device that can transmit and receive the f _b frequency band. Just leave it there. On the other hand, in the area shown in 6, a device that can transmit and receive both frequencies _fa and _fb used for two adjacent beams is installed. If the frequency at which communication is possible is selected from fa or f _b in terms of time, it is possible to always secure _a communication line with the satellite even if the attitude of the satellite changes.

FIG. 4 shows a specific example of the frequency switching method described above. In the figure, 7 is a satellite equipped with a multi-beam antenna, 8 and 9 are radiation beams with frequencies fa and f _b , respectively, 10 is a satellite attitude _change detection device, 11 is a line that transmits the detection signal to the earth station, and 12 is the earth station in area 6, 13 is the switch, 1
4a and _14b are transceivers for frequencies fa and _fb, respectively. Now, when the satellite 7 moves, the direction and amount of the movement is detected by 10, and the information is sent to 12 earth stations via a line 11. As an example of these 11 lines, the following are possible.

(i) The same content of satellite attitude change detection information is included in all radiation beams from the multi-beam antenna mounted on the satellite, and the information is broadcast to the earth station in a broadcast manner. In the example of FIG. 4, the beams shown at 8 and 9 contain the same detection information and are transmitted.

(ii) The detection information is included in a beacon signal etc. from the satellite and transmitted to a monitoring and control station on the ground, and from this station the detection information is transmitted to each earth station via a terrestrial line.

(iii) Include detection information in the beacon signal etc. from the satellite and transmit it directly to each earth station.

Based on the information transmitted in this manner, if it is determined that beam 9 is directed toward the earth station 12, the switch 13 switches the beam to the f _b transmitter/receiver 14b.

For example, assume that beam number 8 is directed to 12 earth stations and they are communicating via f _a , and then beam number 9 is directed to 12 earth stations due to a change in the attitude of the satellite. At this time, as described above, the earth station's transmitter and receiver are switched based on attitude information from the satellite. At this time, the signals from the satellite to the 12 earth stations must naturally be transferred from beam 8 to beam 9, but in this case, the satellite itself cannot determine which beam is currently pointing in the direction of the 12 earth stations. It is possible to make a change for the purpose of

FIG. 5 shows another specific embodiment of the frequency switching method. In the figure, 15 is a received signal branching circuit, and 16 is a received level comparison circuit. Assuming that beams fa _{and fb} are being radiated from the satellite antenna as shown in FIG. 4, the earth station 12 is always enabled to receive beams fa _{and fb} . That is, part of the received signal is branched to 15 branch circuits, and 16 judges which frequency has the largest power. As a result, if f _a is larger than f _b , the switch 13
F _A is switched towards the transceiver. As mentioned above, replacing signals on a satellite is easy because the satellite itself can determine the direction in which the beam from the antenna is pointing.

As explained above, in a communication system using a multi-beam antenna, the transmitting or receiving frequency of an earth station located in an area where the irradiated beam changes due to attitude changes of the satellite is adjusted appropriately to the frequency of the irradiated beam at that time. Since communication is performed by switching between multiple beams, there is an advantage that the service area in which communication can be performed can be increased by using multiple beams. Because of these advantages, it can be applied not only to satellite communications but also to any system that uses a multi-beam antenna, and where the beam direction on the multi-beam antenna side changes over time.

Here, in order to simplify the explanation, the number of beams and the frequency are limited to two, but the number may be two or more. Furthermore, although the shape of the beam has been described as circular, it is not limited to a circular shape either.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing one of the multiple beams, Fig. 2 is an explanatory diagram when a service area is irradiated with multiple beams, Fig. 3 is a diagram illustrating an embodiment of the present invention, and Fig. 4 and FIG. 5 are diagrams showing a specific example of a frequency switching method. 1... Beam center direction, 2... Irradiation area when there is attitude change, 3... Irradiation area when there is no attitude change (beam shape with visual radius θ degrees), 4...
Service area, 5, 5'... Non-irradiation area, 6...
... Area irradiated with any frequency when there is an attitude change, 7 ... Satellite, 8, 9 ... Radiation beam, 10 ... Satellite attitude change detection device, 11 ... Transmission line, 12 ... Earth station , 13... switching device, 14
... Transmitter/receiver, 15 ... Reception signal branch circuit, 16
...Reception level comparison circuit.

Claims (1)

[Claims] 1. In a multi-beam communication system in which a satellite carrying a multi-beam antenna and whose attitude fluctuates over time beams and communicates by beaming a single service area at a different frequency for each beam. , an earth station installed outside the area irradiated by each beam with a predetermined gain or higher and in an area that is always irradiated by one of the beams despite temporal fluctuations in the irradiation beam due to attitude changes of the satellite. A multi-beam communication system that includes a transceiver that can transmit and receive multiple frequencies, and that communicates by switching the frequency to a stronger beam frequency in response to changes in the irradiation beam due to changes in the attitude of the satellite. 2. The multi-beam communication system according to claim 1, in which the amount and direction of the attitude change of the satellite is detected by a satellite attitude change detection device mounted on the satellite, and the transmitting and receiving frequency of the earth station is switched according to the results. 3. The multi-beam communication system according to claim 1, in which the earth station compares the reception levels of each reception beam and switches the transmitting and receiving frequency to the frequency of the beam with the maximum reception level.