Antenna

A self-stabilizing antenna is pivotable about an axis of elevation, a cross-level axis and an azimuth axis. The antenna comprises an antenna member (1) for transfer of signals between said antenna member and a satellite, and a frame member (6) on which the antenna member (1) is mounted for mounting thereof on said movable support. The frame member (6) includes mounting members (7, 8 and 9) permitting pivotal movement of the antenna member about said axes. The antenna further comprises driving units (12, 14) for pivotal movement of the antenna member (1) about said axes, electronic units (21, 22) for sensing and controlling the pivotal movements of the antenna member (1) and for the transfer of signals between the antenna member and a satellite, a signal transformer unit (5), a signal amplifier unit (23), a signal transfer unit (30) and a gyroscope unit (24). For providing an antenna which is kept still during transmission and/or reception of signals from a satellite, said units (5, 12, 14, 21, 22, 23, 24 and 30) are provided such that more than 50% of the total mass of the antenna is concentrated to the antenna member (1) and/or to the frame member (6) in direct connection with the antenna member (FIG. 1).

FIELD OF THE INVENTION

The present invention relates to a self-stabilizing antenna which is pivotable about an axis of elevation, a cross-level axis and an azimuth axis and which is adapted for mounting on a movable support, wherein the antenna comprises an antenna member for transfer of signals between said antenna member and a satellite, and a frame member on which the antenna member is mounted, for mounting said antenna member on said movable support, said frame member including mounting members permitting pivotal movement of the antenna member about said axes, and wherein the antenna further comprises at least one or more driving units for pivotal movement of the antenna member about said axes, one or more electronic units for sensing and controlling the pivotal movements of the antenna member and for the transfer of signals between the antenna member and a satellite, a unit for, inter alia, transforming the signals from the satellite, a unit for amplifying the signals from the satellite, a unit for transferring the signals from the satellite from said signal transformer unit to said signal amplifier unit, and a gyroscope unit.

BACKGROUND OF THE INVENTION

A problem at such an antenna is to keep the antenna still also when the support, preferably a ship, on which the antenna is mounted, is moving in heavy sea.

Two principal conditions for succeeding therewith are on one hand that the friction in bearings and other details for interconnecting the various components and units of the antenna, e.g. cables, is minimal, on the other hand that the mass of the antenna is as large as possible.

Minimal friction is obtained by means of suitable bearings. Low start friction is also important, since many times only relatively small and slow movements are involved.

Cables interconnecting the various components and units electrically, are chosen with regard to mechanical properties for attaining the least torsional resistance alternatively flexural resistance. The attachments for the cables and the connection paths therefor between the various components and units highly affect the movability of the antenna. In order to attain the least possible torsional and flexural resistance, it is possible to use helical cables or large loops of cable which distribute flexural and torsional forces over long sections of the cables.

The requirement that the antenna shall have a large mass is determined in principal by how much the antenna is allowed to weigh, where it will be situated and the stress the attachment therefor can/shall manage. However, for productive and functional reasons it is obviously an advantage if the weight of the antenna is kept low and the size thereof is small.

SUMMARY OF THE INVENTION

In order to, based on such conditions, provide an antenna which is kept still as much as possible during transmission and/or reception of signals from a satellite, it is desired according to the invention that as much as possible of the available mass of the antenna is found in connection with the antenna member.

Therefore, the invention is characterized by the fact that said units forming part of the antenna are provided such that more than 50% of the total mass of the antenna is concentrated to the antenna member and/or to the frame member in direct connection with the antenna member.

According to a preferred embodiment of the invention, this means that at least said one or more electronic units and said signal amplifier unit are mounted on the antenna member and/or on the frame member in direct connection with the antenna member.

The weight the antenna member has attained according to the invention, counter-acts movements of the antenna member, which is important particularly during transfer of signals between the antenna member and a satellite. Thus, in other words, all “heavy” components and units of the antenna are as far as possible mounted on the antenna member or as close as possible thereto in order to thereby make the most use of the mass and get the least influence from friction and rigidness in e.g. bearings and cables.

The abovementioned and other characterizing features of the invention will be further described below with reference to the accompanying drawings.

Thus,FIGS. 1 and 2illustrate a self-stabilizing antenna which is adapted for mounting on a movable support (not shown), preferably a ship. The antenna is pivotable about three axes that extend at an angle relative to each other, namely an axis of elevation A, a cross-level axis B and an azimuth axis C, i.e. the antenna is pivotable in space, in order to maintain the set orientation towards a satellite in e.g. heavy sea.

The antenna comprises an antenna member1, in the illustrated embodiment a parabolic reflector2with a horn3(FIGS. 4 and 5) for transfer of signals between the antenna member and a satellite. The horn3is operable, i.e. rotatable by means of a drive unit4, an electric motor, for correct polarization of the signals. To the horn3there is connected a signal transformer unit in the form of a so called LNB (Low Noise Block)-unit5which transforms the signals from a satellite to a lower and more manageable frequency and amplifies said signals to a suitable level. Said LNB-unit5is also rotated by the polarization motor4.

The antenna member1is mounted on a frame member6of the antenna. The frame member6is used for mounting the antenna member1on the movable support. The frame member6includes mounting members for permitting pivotal movement of the antenna member1about said axes A, B, C. Since said axes A, B, C are three in number, the frame member6includes, in the illustrated embodiment, three mounting members7,8and9, i.e. one mounting member for each axis.

The antenna member1is with the rear side attached to a first mounting member7of the frame member6. This first mounting member7consists of a plate, in the illustrated embodiment a round plate10, surrounded by a flange portion11. The antenna member1is attached to the plate10, preferably screwed onto said plate, and through the flange portion11journalled on a second mounting member8for pivotal movement of the antenna member about the axis of elevation A. A drive unit12, preferably a servo motor of a suitable type, is in the illustrated embodiment located at one of two opposing bearing points for the flange portion11on the second mounting member8for pivoting movement of the first mounting member7, with the antenna member1, about the axis of elevation A. The drive unit12may thereby be mounted on the flange portion11and with an output shaft cooperate with a gear wheel13or other type of transmission which is mounted on the second mounting member8such that said drive unit and along therewith, said first mounting member7and said antenna member1, move around said gear wheel.

The second mounting member8of the frame member6is in the illustrated embodiment shaped as a yoke and the arms of said yoke are connected to the flange portion11of the first mounting member7at said opposing bearing points.

The antenna member1is through the second mounting member8of the frame member6journalled on a third mounting member9of said frame member for pivotal movement about the cross-level axis B. A drive unit14of preferably the same type as drive unit12is in the illustrated embodiment provided to bring about this pivotal movement. Suitably, the drive unit14may thereby be mounted on the second mounting member8and the output shaft thereof cooperate with a gear wheel15or similar which is mounted on the third mounting member9such that said drive unit and along therewith said second mounting member and thus, the first mounting member7with the antenna member1as well, move around said gear wheel.

Through the third mounting member9of the frame member6, the antenna member1is journalled on the movable support for pivotal movement about the azimuth axis C. In the illustrated embodiment, the third mounting member9includes a mounting plate16on which holder plates17and18for the second mounting member8of the frame member6are located for pivotal movement of said second mounting member about the cross-level axis B. A drive unit19of preferably the same type as the drive units12and14is provided to bring about pivotal movement about the azimuth axis C of the holder plates17,18, and thereby of the antenna member1through the first and second mounting members7,8, relative to the mounting plate16. The drive unit19may thereby be mounted on the holder plates17,18and with the output shaft thereof cooperate with a gear wheel20or similar on the mounting plate16such that the entire antenna moves around said gear wheel.

Beyond the abovementioned antenna and frame members1,6and the members, components and units etc. forming part thereof, the antenna comprises one or more electronic units, in the illustrated embodiment two electronic units21and22, for sensing and controlling the pivotal movements of the antenna member1and for the transfer of signals between the antenna member and a satellite. These two electronic units are in the illustrated embodiment formed by a central processing unit (CPU)21and a motor control unit22which are both relatively large and heavy. The construction of the electronic units21,22, i.e. here the CPU21and the motor control unit22, for performing said and eventual other functions does not form part of the present invention and is therefore not described in detail here.

In the illustrated embodiment, the antenna further comprises a unit23for amplifying the signals from the satellite, said signal amplifier unit also being relatively large and heavy, a unit30for transferring the signals from the satellite from said LNB-unit5to said signal amplifier unit23, e.g. a so called OMT (Orthogonal Mode Transducer)-unit, and a gyroscope unit24. Said OMT-unit30is located very close to the LNB-unit5and rotates therewith.

In order to see to, as initially mentioned, that the antenna member1does not move during transfer of signals, but counteract movements by giving the antenna member a large mass such that said antenna member becomes sluggish and difficult to move out of a set position, the units forming part of the antenna, i.e. in the embodiment described above, the LNB-unit5, the drive units4,12,14,19, the CPU21, the motor control unit22, the signal amplifier unit23, the OMT-unit30and the gyroscope unit24, are according to the invention provided such that more than 50% of the total mass of the antenna is concentrated to the antenna member1and/or to the frame member6in direct connection with the antenna member.

In the embodiment illustrated in the drawings, the CPU21, the motor control unit22and the signal amplifier unit23are consequently mounted on the antenna member1and/or on the frame member6in direct connection with the antenna member, as are the drive units4,12, the LNB-unit5and the OMT-unit30. In more detail, for the purpose of the invention, at least the CPU21, the motor control unit22and the signal amplifier unit23are mounted on the rear side of the antenna member1and/or on the frame member6at the rear side of the antenna member, preferably on the first mounting member7of the frame member and thereby most preferably on the plate10of said first mounting member. The CPU21, the motor control unit22and the signal amplifier unit23are mounted on the plate10preferably such that the weight or mass of these units is uniformly distributed on both sides of the axis of elevation A of the antenna member1.

The gyroscope unit24is also found on the plate10of the first mounting member7, while, as already mentioned, the drive unit12is found on the flange portion11of the first mounting member.

Those members, components, drive units etc. which in an application of the invention can not sit on the antenna member1or on the first mounting member7of the frame member6, are located in the best possible way in connection with said antenna member on the subsequent, separately movable members, i.e. primarily on the second mounting member8and secondly on the third mounting member9.

In order to get an optimum distribution of the mass as defined above and simultaneously keeping the total weight of the antenna within the desired interval, at least all members except the antenna member1and the first mounting member7of the frame member6are made as light as possible, e.g. of aluminum since aluminum provides for strength and rigidness in combination with low weight. If the parabolic reflector2of the antenna member1is made of plate sheet, it can not be expected to carry all heavy components which then have to be mounted preferably on the first mounting member7of the frame member6. This first mounting member7should then not be made of light metal. All other components and units are also made in an optimum manner in order to arrive at the defined object of the invention.

The theoretically optimum antenna with regard to its motion pattern and balance, has a common pivoting point for all three at an angle relative to each other extending axes A, B, C. However, such an embodiment where all these axes A, B, C intersect each other in one point, can not be arrived at with a construction according to the present invention with more than 50% of the total mass of the antenna concentrated to the antenna member1and/or to the frame member6in direct connection with the antenna member. In other words, the axes A, B, C must be displaced relative to each other and balancing thereabout be carried through separately.

For balancing, the first, second and third mounting members7,8,9of the frame member6each includes a balancing weight25,26and27respectively. By means of these balancing weights25,26,27, said mounting members7,8,9are balanced about the axis of elevation A, the cross-level axis B and the azimuth axis C respectively, such that said mounting members remain in each position in which they are set. Each balancing weight25,26,27consists, in the illustrated embodiment, of a rod28with a weight29which is displaceable along the rod, but may be of any other suitable construction. The parabolic reflector2of the antenna member1may further include one or more balancing weights (not illustrated) which are rigidly mounted on the rear side of said reflector.

As mentioned above, the mounting members7,8,9are balanced separately, starting with the first mounting member7with the antenna member1. Balancing is carried through statically (find position of equilibrium) such that the centre of gravity is located on its pivot axis (axis of elevation A). Thus, a position is found where the first mounting member7with the antenna member1can be set in any optional angle of elevation without said members swinging back to another position.

Then, the second mounting member8is balanced in a similar way with regard to the cross-level axis B by obtaining a state of equilibrium by means of the balancing weight26thereon, such that any optional angle can be chosen without the mounting member swinging to any side.

Finally, the third mounting member9is balanced about the azimuth axis C in a similar manner by means of the balancing weight27. To this end however, it is required that the entire antenna is turned such that the azimuth axis C is directed horizontally for using the gravity to find the position of equilibrium, i.e. to see which member is swinging downwards by means of the gravity and compensate with the balancing weight in order to find the position of equilibrium.

It is obvious to a skilled person that the present invention can be modified and altered within the scope of the subsequent claims without departing from the idea and purpose of the invention. Thus, beyond what is defined above, the various members, components and units of different types of the antenna may vary in construction in view of their function and so may e.g. the number of electronic units and other components based on the application. It is e.g. possible to use one and the same drive unit for pivotal movement of the antenna member about all three at an angle extending axes.