Claims
- 1. In an antenna pointing device operatively associated with a main offset reflector and a secondary offset reflector and being capable of scanning in two orthogonal directions, said device comprising a fixed source emitting a radio beam, the improvement comprising a set of at least three mirrors and first and second rotary drive mechanisms, said at least three mirrors including a first mirror which is aligned with said secondary reflector and a second and a third mirror which are fixed respectively to said first and second respective rotary drive mechanisms for providing rotary drive about two axes .DELTA. and .DELTA.', respectively extending in orthogonal directions, the direction of the mean axis of the parallel beam between said second and third mirrors being parallel to the axis Z of the beam radiated from the main reflector, said axes of rotation .DELTA. and .DELTA.' being perpendicular to said axis Z of the beam radiated from the main reflector near the zenith of the scanning zone of the antenna, the axis .DELTA.' of rotation of the second mechanism being colinear with the mean axis of the parallel beam 21 from the source which is applied to the third mirror, and the secondary reflector and the first and second mirrors being mechanically interconnected and constituting a moving assembly, said second mechanism operatively driving the third mirror and said first mechanism operatively driving said moving assembly, whereby for aiming trajectories situated in a solid angle near the zenith, the rotations around the axes .DELTA. and .DELTA.' remain small with the antenna well fitted for tracking near that zenith.
- 2. A device according to claim 1, wherein said at least three mirrors further comprises a fourth mirror, said fourth mirror being disposed between the source and the third mirror and forming a further third assembly such that said second mechanism operatively drives both said third and fourth mirrors.
- 3. A device according to claim 1, wherein a lens is disposed between the first mirror and the secondary reflector.
- 4. A device according to claim 1, wherein the mirrors are plane mirrors.
- 5. A device according to claim 1, wherein the mirrors are shaped mirrors.
- 6. A device according to claim 1, wherein each of the drive mechanisms includes a stepdown system.
- 7. A device according to claim 1, wherein each drive mechanism includes a angle encoding system.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 86 00223 |
Jan 1986 |
FRX |
|
BACKGROUND OF THE INVENTION
This is a division of application Ser. No. 000,806, filed Jan. 6, 1987, now abandoned.
The present invention relates to an antenna pointing device capable of scanning in two orthogonal directions.
This type of scan can be provided by using a universal joint type of drive capable of tilting about two axes X and Y, and serving to point an entire antenna assembly. However, the source, sometimes together with radio equipment other than the source, must also be moved with the antenna, thereby increasing the moving mass and giving rise to problems of electrical connection between the antenna and its support.
Such a system capable of tilting about two orthogonal axes may also be used for pointing solely an offset reflector, with the source remaining fixed. However, moving the reflector relative to the source gives rise to a loss of focus which may have an effect, in turn, on the phase relationship of the radiation during large swings and if operating at high frequencies, e.g. higher than 20 GHz.
The present invention seeks to mitigate the above drawbacks by providing a device capable of pointing a beam to perform an X-Y scan about two orthogonal axes.
The present invention provides an antenna pointing device capable of scanning in two orthogonal directions, the device comprising a fixed source emitting a radio beam and associated with a main offset reflector and a secondary offset reflector, the device including the improvement of a set of at least three mirrors, including a first mirror which is aligned with the secondary reflector, and a second and a third mirror which are fixed to two respective rotary drive mechanisms for providing rotary drive about two axes extending in orthogonal directions, the direction of the mean axis of the parallel beam between said second and third mirrors being the axis of the beam radiated from the main receptor, with the axis of rotation of the first mechanism being colinear with the mean axis of the parallel beam between the first and second mirrors, with the axis of rotation of the second mechanism being colinear with the mean axis of the parallel beam from the source which is applied to the third mirror, and with the main and the secondary reflectors and the first and the second mirrors being mechanically interconnected to constitute a moving assembly with the second mechanism driving both the third mirror and said moving assembly.
This invention has the advantage of using two offset reflectors, thereby avoiding shadow areas in the radiation emitted by the main reflector, and thus enabling the overall device to be particularly compact.
The invention also allows the beam radiated by the antenna to be pointed without unfocusing the source and without displacing the reflector in such a way as to produce aberrations in the radiation.
US Referenced Citations (2)
| Number |
Name |
Date |
Kind |
|
4516128 |
Watanabe et al. |
May 1985 |
|
|
4525719 |
Sato et al. |
Jun 1985 |
|
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 1338471 |
Jul 1962 |
FRX |
Divisions (1)
|
Number |
Date |
Country |
| Parent |
806 |
Jan 1987 |
|
Patent Grant
4821045
