Communications: directive radio wave systems and devices (e.g. – Directive – Including antenna orientation
Reexamination Certificate
2001-08-22
2003-03-04
Blum, Theodore M. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including antenna orientation
C342S356000
Reexamination Certificate
active
06529161
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna control method of and an antenna controller for controlling the direction of an antenna beam of an antenna used for either a satellite communication earth station installed in a mobile body, such as an aircraft, or a satellite broadcast receiving facility.
2. Description of the Prior Art
FIG. 10
is a block diagram showing the structure of a prior art antenna controller used for a satellite broadcast receiver for use in aircraft, as disclosed in Japanese patent application publication (TOKKAIHEI) No. 50102895, for example. In the figure, reference numerals
11
-
1
to
11
-n denote receive blocks each of which receives an electric wave from a geostationary satellite by way of its antenna, respectively, reference numeral
12
denotes a common-mode synthesizer for synthesizing n outputs of the antennas of the plurality of receives blocks
11
-
1
to
11
-n after making them in phase with each other, reference numeral
13
denotes on inertial navigation system installed in a mobile body such as an aircraft, reference numeral
15
denotes an orbit data processor for converting orbit data
14
on a geostationary satellite into an electric signal, reference numeral
16
denotes a tracking control unit for generating an electric signal used for mechanical tracking control of the plurality of receive blocks
11
-
1
to
11
-n based on a signal from the inertial navigation system
13
and the signal from the orbit data processor
15
, and for sending the generated electric signal to a driving mechanism
17
mechanically connected to the plurality of receive blocks
11
-
1
to
11
-n, and reference numeral
18
denotes a receiver for receiving a satellite broadcast based on an output of the common-mode synthesizer
12
.
Each of the plurality of receives blocks
11
-
1
to
11
-n shown in
FIG. 10
includes a flat antenna and a BS converter. Each receive block receives an electric wave from the satellite by way of its antenna and then converts the electric wave received to a first intermediate-frequency signal with its BS converter. The common-mode synthesizer
12
converts each of a plurality of first intermediate-frequency signals from the plurality of receives blocks
11
-
1
to
11
-n to a second intermediate-frequency signal, and then synthesizes a plurality of a second intermediate-frequency signals to generate a composite signal after making them in phase with each other and outputs the composite signal to the receiver
18
.
On the other hand, the tracking control unit
16
generates a signal used to control the mechanical tracking of the antenna of each of the plurality of receive blocks
11
-
1
to
11
-n based on an electrical signal from the inertial navigation system
13
installed in the mobile body, which indicates navigation information (i.e., motion information on a motion of the mobile body), and the electrical signal generated by the orbit data processor
15
based on the orbit data
14
on the broadcasting satellite which was input from the outside of the antenna controller in advance, and the tracking control unit
16
then sends the generated signal to the driving mechanism
17
. The driving mechanism
17
directs the antenna of each of the plurality of receive blocks
11
-
1
to
11
-n toward the broadcasting satellite according to the signal used for mechanical tracking control from the tracking control unit
16
. The prior rat antenna controller can thus excellently receive electric waves from the broadcasting satellite whether the mobile body, such as an aircraft, including the controller has an arbitrary attitude, by controlling the mechanical tracking of the antenna of each of the plurality of receive blocks
11
-
1
to
11
-n.
By the way, it is necessary to mount active devices included in the antenna controller in a place of the mobile body where the best possible operating condition is ensured, for instance, a pressure cabin in the case of an aircraft, from the viewpoint of reliability. The prior art antenna controller as shown in
FIG. 10
thus omits a circuit for detecting the direction in which electric waves are coming, which is part of an active device, by using motion information output from the existing inertial navigation system
13
, thus simplifying the antenna controller and improving the reliability of the apparatus.
A problem with the prior art antenna controller constructed as above is that although it is possible to direct the antenna beam toward the broadcasting satellite when the beamwidth of the antenna of each of the plurality of receive blocks is relatively large, it is impossible to direct the antenna beam toward the broadcasting satellite with a high degree of accuracy when the beamwidth of the antenna of each receive block is small because a delay of motion information output from the inertial navigation system negatively affects the tracking accuracy.
In general, information output from the inertial navigation system has an uncertain delay. Assuming that motion information on the true bearing from the inertial navigation system has a delay of 100 msec when the mobile body is an aircraft, if the mobile body inclines rapidly in 30 degrees/s with respect to the true bearing, an error of 3 degrees or less occurs in the inclination of the aircraft though it depends on the direction of the broadcasting satellite and the update cycle of the inertial navigation system. Then, the prior art antenna controller will be unable to catch the direction of the broadcasting satellite momentarily if the beamwidth of the antenna is about 2 degrees. Even if the prior art antenna controller is equipped with a monopulse tracker, the delay of information output from the inertial navigation system is fatal to the system if it has a small antenna beam width because it is thought that the system cannot deal with rapid occurrence of such errors.
SUMMARY OF THE INVENTION
The present invention is proposed to solve the above-mentioned problem, and it is therefore an object of the present invention to provide an antenna control method of and an antenna controller for estimating a delay of navigation information, i.e., motion information sent from an inertial navigation system, estimating current or future motion information on a mobile body such as an aircraft in consideration of the estimated delay, so as to direct an antenna beam toward a geostationary satellite or a mobile satellite with a high degree of accuracy.
In accordance with an aspect of the present invention there is provided an antenna control method for controlling a direction of an antenna beam of an antenna unit installed in a mobile body, for a purpose of satellite communication or satellite broadcast reception using a satellite, the method comprising the steps of: in order to estimate a delay of motion information on a motion of the mobile body which is acquired by an inertial navigation system, separately acquiring motion information on the motion of the mobile body; estimating the delay of the motion information acquired by the inertial navigation system based on the motion information separately acquired in the previous step and the motion information acquired by the inertial navigation system; and calculating a direction of the antenna beam in consideration of the estimated delay to direct the antenna beam toward the satellite.
In accordance with another aspect of the present invention, the separately acquiring step is the step of acquiring the motion information on the motion of the mobile body by using a 3-axis angular-velocity sensor.
In accordance with a further aspect of the present invention, the separately acquiring step is the step of acquiring the motion information on the motion of the mobile body by using a 3-axis magnetic bearing sensor.
In accordance with another aspect of the present invention, there is provided an antenna controller for controlling a direction of an antenna beam of an antenna unit, which is installed in a mobile body, for receiving an electric wave from a geostation
Fukushima Tomoaki
Iida Akio
Shimizu Takeo
Blum Theodore M.
Mitsubishi Denki & Kabushiki Kaisha
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