Communications: radio wave antennas – Antennas – With means for moving directive antenna for scanning,...
Reexamination Certificate
1999-04-08
2001-06-05
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
With means for moving directive antenna for scanning,...
C343S766000, C343S878000
Reexamination Certificate
active
06243046
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an antenna system and more particularly, to an antenna system for executing communications with orbital satellites moving at low earth orbits using antenna units which track such satellite.
BACKGROUND ART
At first, description is made for types of antenna unit based on the conventional technology.
FIG. 8
is a general view showing an example of an antenna unit based on the conventional technology,
FIG. 9
is a view for explaining the principles of the antenna unit shown in
FIG. 8
,
FIG. 10
is a general view showing another example of antenna unit on the conventional technology,
FIG. 11
is a view for explaining the principles of the antenna unit shown in
FIG. 10
,
FIG. 12
is a general view showing still another example of the antenna unit on the conventional technology and
FIG. 13
is a view for explaining the principles of the antenna unit shown in FIG.
12
. Applied to an antenna unit
51
shown in
FIG. 8
is an Az (Azimuth)/E
1
(Elevation) mount system and the antenna unit is mounted on two axes. As shown in
FIG. 9
, this antenna unit
51
is so constructed that it can be rotated around an azimuth angular axis
5
b
as well as around an elevation angular axis
51
a
.
Applied to an antenna unit
61
shown in
FIG. 10
is a X/Y mount system and the antenna unit is mounted on two axes like in the Az/E
1
mount system. This antenna unit
61
is so constructed, as shown in
FIG. 11
, that it can be rotated around an X axis
61
a
as well as around a Y axis
61
b.
Applied to an antenna unit
71
shown in
FIG. 12
is a HA/DEC mount system and the antenna unit is mounted on two axes like in the Az/E
1
mount system or the X/Y mount system. This antenna unit
71
is so constructed, as shown in
FIG. 13
, that it can be rotated around a HA axis
71
a
as well as around a DEC axis
71
b
. It should be noted that, the technology on this type of antenna units
51
,
61
and
71
is described in the reference Antenna Engineering Handbook (edited by Institute of Electronics and Communication Engineers) Chapter 9, Section 5.
Next, description is made for an example in which the antenna unit is applied to a satellite communication system. In recent years, there has received attention on an orbital satellite communication system in which a plurality of satellites are launched in Low Earth Orbits and data transaction is executed through communications with each of the satellites. There is a system called Teledesic in this orbital satellite communication system. In this type of system, each antenna unit located on the ground is required to seize (track) a plurality of orbital satellites one after another while the satellites are within a visible area from the ground and also it is required to continuously insure the communication routes. Namely, each of the antenna units seizes at least two satellites, monitors information for switching satellites by receiving radio waves sent from the satellites all the time, and communicates with the satellites as required through receiving and transmitting radio waves from and to the satellites.
Then, description is made for a relation between an antenna unit and a satellite.
FIG. 14
is a view for explaining a positional relation between the conventional type of antenna system and orbital satellites, and
FIG. 15
is a view for explaining an example of interference of radio waves in the conventional type of antenna system. In the example of
FIG. 14
, two antenna units
51
and
52
each having the same construction and function are installed near each other, and a large number of orbital satellites (among them orbital satellites
81
,
82
and
83
are shown in the figure) orbit in Low Earth Orbit LEO. Herein the reference numeral R
1
shows a radio wave between the antenna unit
51
and an orbital satellite, and the antenna unit
51
receives radio waves from a satellite and transmits radio waves to the satellite if necessary. The reference numeral R
2
shows a radio wave between the antenna unit
52
and an orbital satellite, and the antenna unit
52
receives radio waves from the satellite.
The two orbital satellites
81
,
82
orbiting (moving in the right direction in the figure) in Low Earth Orbit LEO are tracked by the antenna units
51
,
52
respectively, and communication routes are set between the Low Earth Orbit LEO and the ground. Namely, the antenna unit
51
is tracking the orbital satellite
81
, and the antenna unit
52
is tracking the orbital satellite
82
. At this point of time, for example, the antenna unit
51
performs satellite communication (communications through data transaction) with the orbital satellite
81
, and on the other hand the antenna unit
52
receives satellite switching information from the orbital satellite
82
.
Then, when the orbital satellite
81
is out of vision from the ground, namely can not be seized by the antenna unit
51
, the satellite communications are performed by switching to the communication route formed between the antenna unit
52
and the orbital satellite
82
. The timing of this switching is decided according to the satellite switching information sent from the orbital satellite
82
to the antenna unit
52
before switching. This switching is executed instantly. Thus, when switching of satellites is to be performed mechanically, two antenna units
51
and
52
are required. When the satellites are switched, the antenna unit
51
starts tracking the orbital satellite
83
skipping the next orbital satellite
82
. Then, for next switching of the satellites because the antenna unit
52
can not seize the orbital satellite
82
any more, the antenna unit
51
starts receiving satellite switching information, from the orbital satellite
83
, for switching the communication route used for satellite communications between the antenna unit
52
and orbital satellite
82
to that between the antenna unit
51
and the orbital satellite
83
.
As described above, in the next switching of satellites, the antenna unit
51
is required to switch to the orbital satellite
83
as instantaneously as possible, and at that point of time, dead angles need to be reduced as much as possible. Accordingly, when orbital satellites are tracked using the mechanical method, it is important to efficiently perform synchronization between the two antenna units
51
and
52
.
In order to achieve this, it is required to provide the antenna units
51
and
52
as close as possible, but if the antenna system is so constructed that one of radio routes comes into even just a portion of the other radio route between the antenna units
51
and
52
, interference of radio waves may occur between the radio route L
1
in the antenna unit
51
and radio route L
2
in the antenna unit
52
. Therefore, a blocking portion (interfering portion) Z
1
due to radio waves of the antenna unit
51
may occur in the antenna unit
52
, and a blocking portion Z
2
due to radio waves of the antenna unit
52
may occur in the antenna unit
51
, which reduces the reliability of satellite tracking and satellite switching.
The present invention has been made for solving the problem described above, and it is an object of the present invention to obtain an antenna system in which interference does not occur even if a plurality units of antenna unit are provided at the closest possible distance between the devices and also tracking orbital satellites and switching satellites can reliably be executed.
DISCLOSURE OF THE INVENTION
In the present invention, in order to locate a plurality of antenna units each rotating around a plurality of different rotation axes respectively, a plurality of antenna units are arranged on a pedestal device having one rotation axis symmetric with respect to the rotation axis, and each of the antenna units are allowed to rotate around a plurality of different rotation axes, so that each of the antenna units rotates around the rotation axis of the pedestal device and also rotates around the rotation axis of its own, and therefore, it is possible to provide an an
Ho Tan
Mitsubishi Denki & Kabushiki Kaisha
Rothwell Figg Ernst & Manbeck
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