GB2151851A

GB2151851A - Antenna drive

Info

Publication number: GB2151851A
Application number: GB08419901A
Authority: GB
Inventors: Richard Cresswell
Original assignee: General Electric Co PLC
Current assignee: General Electric Co PLC
Priority date: 1983-12-16
Filing date: 1984-08-03
Publication date: 1985-07-24
Also published as: GB8419901D0; GB2151851B; AU3681384A

Abstract

An antenna is pivoted on a mounting about a first axis (3) and is driven by a screw threaded drive member (5) to which it is pivoted about a second axis (4). The drive member (5) engages a drive mechanism (6) which is pivoted about a third axis (7) which is fixed inspace all the axes being parallel. At one position of adjustment the second and third axes (4,7) are in line with each other enabling the drive member (5) to be pivoted through 180 DEG thereby doubling the size of the arc through which the antenna can be rotated. <IMAGE>

Description

SPECIFICATION Antenna drive This invention relates to an antenna drive. In one conventional type of antenna drive system the antenna is caused to scan repetitively through an arc of 80 or 90 degrees by a longitudinal screw threaded drive member which is moved to and fro by an electrically operated drive mechanism engaging with the screw thread. In such systems the screw threaded drive member is pivoted to the antenna structure and the drive is pivoted to a fixed mounting structure so as to accommodate relative turning movements between those parts during operation of the drive. It is sometimes desired to adjust the mounting of the antenna so that it scans through a different arc. Hitherto, in order to effect such adjustment it has been necessary to unbolt the antenna drive from its mounting and re-bolt it at an alternative position.This is obviously a very time consuming exercise and it is of course impracticable to make such adjustment whilst tracking a target which may move from one of the said arcs to the other. It was with this problem in mind that the present invention arose.

The invention provides an antenna drive system comprising an antenna structure pivoted on a mounting about a first axis, a longitudinal drive member pivoted to the antenna structure about a second axis, and a drive mechanism pivoted to the mounting about a third axis and arrange to drive the drive member longitudinally so as to cause rotation of the antenna structure through an arc; the second and third axes being arranged to be co-linear at one point of movement of the drive member, enabling the drive member and drive mechanism to be pivoted to an opposite side of a plane containing the first and second axes. By pivoting the drive member and drive mechanism in this way the antenna can be made to scan, at the choice of the operator, through one or other of two possible arcs.Alternatively, if some automatic mechanism is provided to pivot the drive mechanism and drive member each time the position is reached when such pivoting can take place, the antenna can be made to scan through twice the arc which would otherwise be possible.

The invention is also applicable to a tracking system in which the antenna is driven in a direction so as to follow the movement of a target. In such a tracking system it is sometimes required that the antenna should oscillate or rotate about a mean direction which is known to be the approximate direction of the target. This enables the system to steer the antenna so that its mean direction follows movement of the target. In such a system, in order that the antenna should be able to oscillate or rotate about that direction which it adopts when the second and third axes are co-linear, the designs preferably allows the second axis to be driven through and slightly beyond the point where it is co-linear with the third axis during movement of the antenna through the or each arc.

It is envisaged that the invention will find greatest application for effecting scanning movement in azimuth but it will be appreciated that the invention could equally well be adapted to cause scanning in elevation.

One way in which the invention may be performed will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a plan view of apparatus con structed in accordance with the invention in the position where pivoting of the drive member and drive mechanism can take place; Figure 2 shows an elevational view of part of the apparatus shown in Figure 1; Figure 2A shows an alternative construction to that shown on Figure 2; and Figures 3and 4 show the apparatus of Figures 1 and 2 in extreme positions of pivoting movement to the right and left respectively.

Referring to Figures 1,2,3 and 4 of the drawings an antenna structure indicated generally by reference 1 includes a radius arm 2 which carries an antenna 2A and is pivoted about a first vertical axis 3 to a fixed mounting structure (not shown).

The radius arm 2 is pivoted about a second vertical axis 4 to one end of a drive member in the form of a screw threaded shaft 5 which is driven longitudinally by an electrically operated drive mechanism. The drive mechanism 6, which works along conventional principles, is seen best in Figure 3 and is unconventional in that it has two arms 6A (only one of which is shown in Figures 1,2 and 4) which extend towards the second axis 4 and by which the drive mechanism is pivoted, about a third axis 7, to the fixed mounting structure.

When the parts 5,6 and 7 are in the position shown in full lines on Figure 1, operation of the drive mechanism 6 will drive the antenna through the arc indicated to a1 to the position shown in Figure 3.

Alternatively, starting from the position illustrated in Figures 1 and 2, where it is to be noted that the axes 4 and 7 are in line with each other, the parts 5 and 6 can be pivoted through 180 to the position as shown in broken lines in Figure 1. Such pivotting taking place through the imaginary plane P containing the axes 3 and 7. After making this adjustment, operation of the drive mechanism 6 will cause the antenna structure to pivot through the arc a2 to the position shown in Figure 4. Thus a total arc of a1 + a2 can be covered without a major close down of the installation.

Should it prove difficult in a particular application to arrangeforthe pivotforthe drive assembly as shown in Figure 2 an alternative arrangement can be adopted as is shown in Figure 2A where the drive assembly is mounted on a turntable arrangement 8.

1. An antenna drive system comprising an antenna structure pivoted on a mounting about a first axis, a longitudinal drive member pivoted to the antenna structure about a second axis, and a drive mechanism pivoted to the mounting about a third axis and arranged to drive the drive member longitudinally so as to cause rotation of the antenna structure through an arc; the second and third axes being arranged to

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Antenna drive This invention relates to an antenna drive. In one conventional type of antenna drive system the antenna is caused to scan repetitively through an arc of 80 or 90 degrees by a longitudinal screw threaded drive member which is moved to and fro by an electrically operated drive mechanism engaging with the screw thread. In such systems the screw threaded drive member is pivoted to the antenna structure and the drive is pivoted to a fixed mounting structure so as to accommodate relative turning movements between those parts during operation of the drive. It is sometimes desired to adjust the mounting of the antenna so that it scans through a different arc. Hitherto, in order to effect such adjustment it has been necessary to unbolt the antenna drive from its mounting and re-bolt it at an alternative position.This is obviously a very time consuming exercise and it is of course impracticable to make such adjustment whilst tracking a target which may move from one of the said arcs to the other. It was with this problem in mind that the present invention arose. The invention provides an antenna drive system comprising an antenna structure pivoted on a mounting about a first axis, a longitudinal drive member pivoted to the antenna structure about a second axis, and a drive mechanism pivoted to the mounting about a third axis and arrange to drive the drive member longitudinally so as to cause rotation of the antenna structure through an arc; the second and third axes being arranged to be co-linear at one point of movement of the drive member, enabling the drive member and drive mechanism to be pivoted to an opposite side of a plane containing the first and second axes. By pivoting the drive member and drive mechanism in this way the antenna can be made to scan, at the choice of the operator, through one or other of two possible arcs.Alternatively, if some automatic mechanism is provided to pivot the drive mechanism and drive member each time the position is reached when such pivoting can take place, the antenna can be made to scan through twice the arc which would otherwise be possible. The invention is also applicable to a tracking system in which the antenna is driven in a direction so as to follow the movement of a target. In such a tracking system it is sometimes required that the antenna should oscillate or rotate about a mean direction which is known to be the approximate direction of the target. This enables the system to steer the antenna so that its mean direction follows movement of the target. In such a system, in order that the antenna should be able to oscillate or rotate about that direction which it adopts when the second and third axes are co-linear, the designs preferably allows the second axis to be driven through and slightly beyond the point where it is co-linear with the third axis during movement of the antenna through the or each arc. It is envisaged that the invention will find greatest application for effecting scanning movement in azimuth but it will be appreciated that the invention could equally well be adapted to cause scanning in elevation. One way in which the invention may be performed will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a plan view of apparatus con structed in accordance with the invention in the position where pivoting of the drive member and drive mechanism can take place; Figure 2 shows an elevational view of part of the apparatus shown in Figure 1; Figure 2A shows an alternative construction to that shown on Figure 2; and Figures 3and 4 show the apparatus of Figures 1 and 2 in extreme positions of pivoting movement to the right and left respectively. Referring to Figures 1,2,3 and 4 of the drawings an antenna structure indicated generally by reference 1 includes a radius arm 2 which carries an antenna 2A and is pivoted about a first vertical axis 3 to a fixed mounting structure (not shown). The radius arm 2 is pivoted about a second vertical axis 4 to one end of a drive member in the form of a screw threaded shaft 5 which is driven longitudinally by an electrically operated drive mechanism. The drive mechanism 6, which works along conventional principles, is seen best in Figure 3 and is unconventional in that it has two arms 6A (only one of which is shown in Figures 1,2 and 4) which extend towards the second axis 4 and by which the drive mechanism is pivoted, about a third axis 7, to the fixed mounting structure. When the parts 5,6 and 7 are in the position shown in full lines on Figure 1, operation of the drive mechanism 6 will drive the antenna through the arc indicated to a1 to the position shown in Figure 3. Alternatively, starting from the position illustrated in Figures 1 and 2, where it is to be noted that the axes 4 and 7 are in line with each other, the parts 5 and 6 can be pivoted through 180 to the position as shown in broken lines in Figure 1. Such pivotting taking place through the imaginary plane P containing the axes 3 and 7. After making this adjustment, operation of the drive mechanism 6 will cause the antenna structure to pivot through the arc a2 to the position shown in Figure 4. Thus a total arc of a1 + a2 can be covered without a major close down of the installation. Should it prove difficult in a particular application to arrangeforthe pivotforthe drive assembly as shown in Figure 2 an alternative arrangement can be adopted as is shown in Figure 2A where the drive assembly is mounted on a turntable arrangement 8. CLAIMS

1. An antenna drive system comprising an antenna structure pivoted on a mounting about a first axis, a longitudinal drive member pivoted to the antenna structure about a second axis, and a drive mechanism pivoted to the mounting about a third axis and arranged to drive the drive member longitudinally so as to cause rotation of the antenna structure through an arc; the second and third axes being arranged to be co-linear at one point of movement of the drive member, enabling the drive member and drive mechanism to be pivoted to an opposite side of a plane containing the first and second axes.

2. An antenna drive system substantially as described with reference to Figures 1,2,3 and 4 on Figures 1, 2A, 3 and 4 of the accompanying drawings and substantially as illustrated therein.