JPH10107717A - Communication satellite on non-geosynchronous orbit and beam arrangement method for communication satellite on nongeosynchronous orbit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize frequencies by providing a means by which a geosynchronous orbit satellite communication system and a non- geosynchronous orbit satellite communication system use the same frequency band in common. SOLUTION: A directivity of a radiation beam is set to a direction shifted from a point beneath a non-geosynchronous orbit satellite Li by a shift angle Δso as to part the radiation beam from a line segment tying the non- geosynchronous orbit satellite Li and a geosynchronous orbit satellite G by a prescribed angle or over. Thus, the directivity of the beam from the non- geosynchronous orbit satellite Lo is selected so that not a non-geosynchronous orbit satellite Li+1 but the non-geosynchronous orbit satellite Li covers a radiation area AtI+1, Thus, the interference between the radiation beam by the geosynchronous orbit satellite G and that of the non-geosynchronous orbit satellite Li is reduced and the geosynchronous orbit satellite communication system and the non-geosynchronous orbit satellite communication system can use a same frequency band in common.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-geostationary-orbit communication satellite beam arrangement method and a non-geostationary-orbit communication satellite used in a satellite communication system using a non-geostationary-orbit communication satellite. About.

[0002]

2. Description of the Related Art FIG. 8 shows an example of a satellite communication system using a geosynchronous orbit communication satellite and a satellite communication system using a non-geostationary orbit communication satellite. In this figure, the geosynchronous orbit satellite communication system includes a geosynchronous orbit communication satellite G and its directional beam B _G
This is a system for performing communication by transmitting and receiving radio waves to and from a satellite communication earth station located in an area _AG irradiated by the radio wave.

On the other hand, the non-geostationary-orbit satellite communication system includes a plurality of non-geostationary-orbit communication satellites L ₁ ,..., L _i , L _{i + 1} ,.
≧ 1), the directional beam B ₁ of each satellite,
Areas A ₁ ,... Illuminated by..., B _i , B _{i + 1} ,.
Communication is performed by transmitting and receiving radio waves to and from a satellite communication earth station of a non-geostationary orbit satellite communication system within A _i , A _{i + 1} ,. In such a non-geostationary orbit satellite communication system, in order to increase the elevation angle of the communication satellite viewed from the satellite communication earth station, for the purpose of facilitating antenna fabrication, etc.,
As shown in FIG. 9, the irradiation area of a non-geostationary-orbit communication satellite is generally set to an area centered directly below each satellite.
FIG. 9 shows the ITU-R Document; 'Report of the Meeting
of Working Party 4A of Radio Communication Study G
roup 4 (GENEVA, 20-29 March 1996) ', Document 4A / 65 (1
996, April) is an example of the irradiation beam arrangement of the conventional non-geostationary orbit communication satellite system, in which the beam irradiation area is the non-geostationary orbit communication on the orbit plane (straight line in the figure) of each non-geostationary orbit satellite. The figure shows a state set in an area (circle in the figure) centered directly below the satellite (black circle in the figure).

[0004]

As shown in FIG. 8, when a geosynchronous orbit satellite communication system and a non-geostationary orbit satellite communication system coexist and both systems use the same frequency band, frequency interference occurs. May occur. In particular, in the earth stations G _{i + 1} and G _{i + 2} of the geosynchronous orbit satellite communication system as shown in FIG. 10, a line connecting the geosynchronous orbit communication satellite G and the earth stations G _{i + 1} and G _{i + 2} is drawn. non-geostationary orbit communications satellites _{L i + 1, L i +} 2 passes, and a non-geosynchronous orbit communication satellites _{L i + 1, L i +} 2 of the irradiated area _{a i + 1, a i +} 2 earth station in the G The largest mutual interference occurs when _{i + 1} and Gi _{+ 2} are present. For this reason, it has been difficult to use the same frequency band between both systems.

An object of the present invention is to solve this problem, to provide means for enabling the same frequency band to be shared between a geosynchronous orbit satellite communication system and a non-geostationary orbit satellite communication system, and to achieve effective use of frequencies. And

[0006]

According to a first aspect of the present invention, there is provided a non-geostationary-orbit communication satellite orbiting a non-geostationary-orbit of the earth, a position in a geostationary-satellite orbit having the same longitude as the non-geostationary-orbital communication satellite, and the earth. In the plane determined by the center of the non-geostationary orbit communication satellite, the beam of the directional beam is separated from the straight line connecting the non-geostationary orbit communication satellite and the position in the geostationary satellite orbit by a certain angle to the north and south from the straight line. It is characterized by controlling the directivity direction.

According to a second aspect of the present invention, there is provided the beam positioning method for a non-geostationary-orbit communication satellite according to the first aspect, wherein the satellite communication system uses a non-geostationary-orbit communication satellite orbiting the earth in a non-geostationary orbit. When both systems of the satellite communication system using the geosynchronous orbit communication satellite communicate with each other using the same frequency band, the non-geostationary orbit communication satellite communicates with the geostationary orbit communication satellite to the earth station. On the other hand, the pointing direction of the beam of the non-geostationary-orbit communication satellite is controlled so that the earth station does not become a large interference source with respect to the non-geostationary-orbit communication satellite.

According to a third aspect of the present invention, there is provided a non-geostationary-orbit communication satellite orbiting the earth in a non-geostationary-orbit communication space between the non-geostationary-orbit communication satellite and a geostationary-satellite orbit at the same longitude as the non-geostationary-orbit communication satellite. In the plane determined by the center of the non-geostationary orbit communication satellite, the beam of the directional beam is separated from the straight line connecting the non-geostationary orbit communication satellite and the position in the geostationary satellite orbit by a certain angle to the north and south from the straight line. It is characterized by comprising means for controlling the directivity direction.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A beam arrangement method according to the present invention comprises:
As shown in FIG. 1, the non-geosynchronous orbit communication satellites L _i and non-geostationary orbit communication satellites L _i and geostationary orbit communications satellites G in the same longitude plane
From the straight line connecting the bets, and controls the directivity direction of the beam so as to release the directional beam of the non-geosynchronous orbit communication satellites L _i of the non-geosynchronous orbit satellite communication system predetermined angle or more.
Here, although the to describe the case where the geostationary orbit position of the non-geosynchronous orbit communication satellites L _i in the same longitude plane is geostationary communications satellites G, and if there is no geostationary communications satellites in geostationary orbit position also The same is true. In the example shown in FIG. 1, to set the orientation of the radiation beam in a direction moved by the moving angle Δ from beneath the non-geosynchronous orbit communication satellites L _i, thereby, the irradiation beam of the non-geosynchronous orbit communication satellites L _i The irradiation beam Bi 'is separated from the straight line by a certain angle or more.

The beam arranging method according to the present invention is applied to a situation where a geostationary orbit satellite communication system and a non-geostationary orbit satellite communication system as shown in FIG. 10 are mixed. Here, in FIG. 10, as described above, the case where the non-geostationary-orbit communication satellite L _{i + 1} passes on a straight line connecting the earth station G _{i + 1} and the geostationary-orbit communication satellite G, that is, Earth station G within irradiation area A _{i + 1 of} orbital communication satellite L _{i + 1
When i + 1} exists, the largest mutual interference occurs.

On the other hand, in the beam arranging method according to the present invention shown in FIG. 1, the non-geostationary-orbit communication satellite L _{i + 1} does not cover the irradiation area A _{i + 1} but the non-geostationary-orbit communication satellite L _i. There directivity direction of the beam of non-geostationary orbit communication satellites L _i to cover the irradiation area a _{i + 1} is set. As a result, the mutual interference between the irradiation beam from the geostationary orbit communication satellite and the irradiation beam from the non-geostationary-orbit communication satellite is reduced. It becomes possible to share the same frequency band.

Hereinafter, embodiments of the present invention will be described more specifically. FIG. 2 is a diagram showing the relationship between a non-geostationary-orbit communication satellite and a geostationary-orbit communication satellite in the same longitude plane as the non-geostationary-orbit communication satellite. Each symbol in this figure represents the following. R: Earth radius h: a non-geostationary orbit communications satellite altitude H: geosynchronous altitude alpha _i: latitude L _i of non-geostationary orbit communications satellites: non-geostationary orbit communications satellites G: L _i and geostationary orbit in the same longitude plane communication satellite E _G: intersection of the geosynchronous orbit communication satellites and non-geostationary orbit communications satellites and the connecting line and the ground surface C: center of the earth

[0013] Here, the non-geosynchronous orbit communication satellites L _i, the center of the earth C, and focusing on the triangle L _i CG made of geostationary orbital positions G of L _i same longitude plane and a straight line L _i distance between G l _i ,
The angle β _i and the angle γ _i are obtained by the following equations using the second cosine theorem and the sine theorem.

(Equation 1)

(Equation 2)

(Equation 3)

FIG. 3 is a diagram showing an irradiation area in which the directional beam of the non-geostationary-orbit communication satellite is moved from immediately below the satellite to the low-latitude side in the low-latitude region. FIG. FIG. 5 is a diagram showing an irradiation area in which the object has been moved to the low latitude side from immediately below the satellite. In these figures, reference numeral F _H, F _L, phi, respectively, are F _H: boundary F of high latitude side of the moved illuminated areas _L: boundary lower latitudes side of the moved illuminated areas phi: non-geostationary orbit communication satellites L _i And a straight line connecting the geosynchronous orbit communication satellite G in the same longitude plane and a straight line L _i F _H indicating the boundary on the high latitude side of the irradiation beam.

Here, focusing on the non-geostationary-orbit communication satellite L _i , the center C of the earth, and the triangle L _i CF _{H formed} by the boundary F _H on the high latitude side of the moved irradiation area, the straight line L _i C and the straight line L _i F _H
The angle x _i formed by the angle E _G L _i F _{H in} a high-latitude region even if the beam irradiation area is directly below the non-geostationary-orbit communication satellite.
Considering that it is possible to make more than the required minimum value φ,
It can be obtained as in the following equation.

(Equation 4) Here, x ′ is an angle of １ ／ of the beam irradiation width when the irradiation beam is right below the non-geostationary orbit communication satellite.

Further, a straight line L_iF_HAnd straight line CF_HCorner
(Ε_1i+90), straight line L_iC and straight line CF _HAngle y_i
Is determined by the following equation.

(Equation 5)

(Equation 6)

Accordingly, the latitude θ _1i of the boundary F _H on the high latitude side of the moved irradiation area is obtained by the following equation. In the vicinity of the equator, the communication beams of the non-geostationary-orbit communication satellites located on the northern hemisphere side and the non-geostationary-orbital communication satellites located on the southern hemisphere side will not overlap because the irradiation beams move to the low latitude side. The beam is not irradiated on the hemisphere on the opposite side of the hemisphere where is located.

(Equation 7)

Further, the latitude theta _2i boundary F _L of the lower latitudes side of the moved illuminated area, if the coverage of the non-geosynchronous orbit satellite communication system attempts to set without a gap, high latitudes of the adjacent non-geostationary orbit communications satellites Since it is necessary to make contact with the boundary on the side, it is obtained by the following equation.

(Equation 8) However, i = 0 indicates the non-geostationary-orbit communication satellite closest to the equatorial plane among the non-geostationary-orbit communication satellites in the northern hemisphere and the southern hemisphere.

The irradiation area of the directional beam obtained as described above is, as shown in FIG. 5, a fixed angle φ or more from a straight line between the geosynchronous orbit communication satellite and the non-geostationary orbit communication satellite in the same longitude plane. You will always be away.

In the above embodiment, the amount of movement of the irradiation beam from the area immediately below the communication satellite changes depending on the latitude of the non-geostationary-orbit communication satellite, but the amount of movement required when the non-geostationary-orbit communication satellite passes on the equator Can be maintained at a required angle φ even when the is fixedly used. FIG. 6 shows an example of the irradiation area in this case.
Shown in

FIG. 7A shows an example of the antenna directivity characteristics of the non-geostationary-orbit communication satellite. In addition, FIG.
FIG. 5 is a diagram showing a definition of a separation φ on a horizontal axis in antenna directivity characteristics. As shown in FIG. 7A, the power of transmitting and receiving radio waves between an earth station and a non-geostationary-orbit communication satellite located at a certain angle away from the irradiation beam is significantly lower than that in the irradiation beam region. For example, the separation φ is about 15 (degr
In ee), the amount of interference from the non-geostationary-orbit communication satellite to the earth station of the geostationary-orbit satellite communication system or the amount of interference from the earth station of the geostationary-orbit satellite communication system to the non-geostationary-orbit communication satellite is 3
5 (dB) can be reduced. Therefore, when the beam irradiation area of the non-geostationary-orbit communication satellite is set by the above-described method according to the present invention, when the non-geostationary-orbit communication satellite passes on a straight line between the earth station and the geostationary-orbit communication satellite in the geostationary-orbit satellite communication system, However, since the minimum required distance φ between this straight line and the irradiation beam of the non-geostationary-orbit communication satellite is always guaranteed, even if a common frequency band is used between the geostationary-orbit satellite communication system and the non-geostationary-orbit satellite communication system. Mutual interference can be extremely small,
Frequency sharing becomes possible.

[0022]

As described above, according to the present invention, the directional beam of the non-geostationary-orbit communication satellite is separated from the straight line connecting the non-geostationary-orbit communication satellite and the position in the geostationary-satellite orbit by a certain angle north and south. Since the beam directing direction is controlled, even when the non-geostationary-orbit communication satellite passes on a straight line between the earth station and the geostationary-orbit communication satellite in the geostationary-orbit satellite communication system, this straight line and the non-geostationary-orbit communication satellite The minimum required separation between the irradiation beams is always guaranteed. As a result, even if a common frequency band is used between the geosynchronous orbit satellite communication system and the non-geostationary orbit satellite communication system, mutual interference can be extremely reduced. The effect that utilization can be aimed at is obtained. Further, when using the beam placement method and the non-geostationary orbit communication satellite according to the present invention,
There is also an advantage that the non-geostationary-orbit satellite communication system does not need the position information of the earth station and the position information of the geostationary satellite in the geostationary-orbit satellite communication system.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example in which an irradiation beam of a non-geostationary-orbit communication satellite is moved from immediately below the satellite to a low-latitude region.

FIG. 2 is a diagram showing a relationship between a communication satellite of a non-geostationary orbit satellite communication system and a geosynchronous orbit position in the same longitude plane.

FIG. 3 is a diagram showing an irradiation area in which a directional beam of a non-geostationary-orbit communication satellite has moved to a low latitude side from immediately below the satellite in a low latitude region.

FIG. 4 is a diagram showing an irradiation area in which a directional beam of a non-geostationary orbit communication satellite has been moved from immediately below the satellite to a lower latitude side in a high latitude region.

FIG. 5 is a diagram showing an example of a beam arrangement of a non-geostationary orbit communication satellite according to the present invention.

FIG. 6 is a diagram showing another example of a beam arrangement of a non-geostationary orbit communication satellite according to the present invention.

FIG. 7 is a diagram illustrating an example of antenna directivity characteristics of a non-geostationary-orbit communication satellite.

FIG. 8 is a diagram illustrating a geosynchronous orbit satellite communication system and a non-geostationary orbit satellite communication system.

FIG. 9 is a diagram showing an example of an arrangement of irradiation beams in a conventional non-geostationary orbit satellite communication system.

FIG. 10 is a diagram illustrating an example of radio wave interference between a geostationary orbit satellite communication system and a non-geostationary orbit satellite communication system.

[Explanation of symbols]

Illumination beam G geostationary orbit communications moving the directivity direction of A _i non-geostationary orbit communications satellites L _i illuminated area A _i non-geostationary orbit communications satellites L _i 'non-geostationary orbit communications satellites L _i illumination area B _i and the movement of' the right under satellite L ₁ ~L _{i + 1} non-geostationary orbit communications satellites

Claims (3)

[Claims] 1. A non-geostationary-orbit communication satellite orbiting the earth in a non-geostationary orbit, a position in a geosynchronous satellite orbit at the same longitude as the non-geostationary-orbit communication satellite, and a plane determined by the center of the earth. Non-geostationary orbit characterized by controlling a beam pointing direction of a geosynchronous orbit communication satellite so as to be at least a fixed angle north and south from a straight line connecting the non-geostationary orbit communication satellite and a position on the geostationary satellite orbit. How to place a beam on a communication satellite. 2. A satellite communication system using a non-geostationary orbit communication satellite orbiting a non-geostationary orbit of the earth and a satellite communication system using a geosynchronous orbit communication satellite communicate with each other using the same frequency band. Is performed, the non-geostationary-orbit communication satellite does not become a large interference source with respect to the earth station communicating with the geosynchronous-orbit communication satellite, or the earth station does not interfere with the non-geostationary-orbit communication satellite. The beam positioning method for a non-geostationary-orbit communication satellite according to claim 1, wherein the direction of the beam of the non-geostationary-orbit communication satellite is controlled as described above. 3. A non-geostationary-orbit communication satellite orbiting the earth in a non-geostationary orbit is determined by the non-geostationary-orbit communication satellite, a position in a geostationary-satellite orbit at the same longitude as the non-geostationary-orbit communication satellite, and a center of the earth. Means for controlling a beam pointing direction of the non-geostationary-orbit communication satellite so as to be at least a certain angle north and south from a straight line connecting the non-geostationary-orbit communication satellite and a position in the geostationary satellite orbit in a plane where A non-geostationary orbit communication satellite comprising: