Communications: directive radio wave systems and devices (e.g. – Directive – Including a satellite
Patent
1988-10-17
1991-01-15
Blum, Theodore M.
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a satellite
H04B 7185
Patent
active
049857061
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present relates to a process or method for data transmission by means of a geo-stationary satellite and at least one sub-satellite, whereby the sub-satellites are located on lower orbit paths.
DESCRIPTION OF THE PRIOR ART
News satellites generally travel along a geo-stationary circular orbit bath at an altitude of approximately 36000 km above the equator. There, the satellites have a strictly allotted orbital position so that the same transmission frequency may be used for each satellite because of the distance between two neighboring satellites. Because the geo-stationary orbit is slowly becoming filled, other satellite orbit paths are being planned, for example, sub-satellite orbit paths with an altitude of a few hundred km or so-called quasi-stationary orbit paths. Details in this context are given in the literature, for example, in: NTZ-Archiv Vol. 5 (1983), Booklet 12, pages 327-335".
The gravest disadvantage therein is that different frequency ranges must be used to preclude mutual interferences. Namely, it is not simply possible with conventional transmission methods to use the same frequency for the geo-stationary satellite and for the sub-satellite, because this would disturb the geo-stationary satellite, particularly because during their visibility, satellites having lower orbital paths pass by several geo-stationary satellites (with respect to the radiating direction of the transmitting earth radio station) which in this case use the same frequency band. However, frequency ranges or transmission band widths are strictly internationally regulated and distributed so that they may not simply be used as desired. Thus, in order to provide for future communication requirements, additional possibilities must be provided.
OBJECT OF THE INVENTION
It is the object of the invention to provide a method of the initially described type which makes it possible to make do with the current (or prescribed) frequency ranges.
SUMMARY OF THE INVENTION
According to the invention, this is achieved in that for communication transmissions at least two data streams of the same carrier frequency, but with different powers are used, whereby the first data stream with a higher powers is used for linking with the geo-stationary satellite and the further data streams are transmitted by means of PN (pseudo-noise) sequences and serve for linking with the sub-satellite or sub-satellites.
Thus, two data transmissions take place with the same carrier frequency whereby, however, different satellites are served.
BRIEF DESCRIPTION OF THE DRAWINGS
Details of the invention are given in the dependent claims and the description, in which an example embodiment is explained in detail in conjunction with the drawings, wherein:
FIG. 1 shows schematically the arrangement of the satellite orbital paths and the area of interference during transmission at the same carrier frequency f.sub.B ;
FIG. 2 shows schematically the principle of spreading by means of PN sequences;
FIG. 3a shows the conditions in the transponder of the geo-stationary satellite without reception of the interfering power; and
FIG. 3b shows the conditions in the transponder of the geo-stationary satellite with reception of the interfering or noise power.
DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE BEST MODE
OF THE INVENTION
FIG. 1 schematically shows the arrangement of the satellite orbit paths. The news satellite S.sub.1 is located on a geo-stationary orbit path at a distance of approximately 36000 km altitude, and the sub-satellite S.sub.2 is located on a sub-satellite orbit path at a distance of approximately 400 km altitude. Satellite S.sub.2 receives data from an earth station E.sub.1. Satellite S.sub.2 receives data from a further earth station E.sub.2. As can be seen in FIG. 1, an interference region is formed in which the two cones of the transmitting antennas overlap. For this reason, as initially mentioned, it is not simply possible to use the same carrier frequency for both earth stations.
According to
REFERENCES:
patent: 4839656 (1989-06-01), O'Neill et al.
Blum Theodore M.
Fasse W. G.
Kane, Jr. D. H.
Messerschmitt-Boelkow-Blohm GmbH
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