Robot-based Precise Offset-Focus Feed Control System Used in the Compact Antenna Test Range

In the Compact Antenna Test Range system, the high-precision feed positioning device can improve the electromagnetic characteristics of the system. In this paper, a new type of precise offset-focus feed positioning device is designed and applied in the antenna test. The positioning device is composed of feed horns, a honeycomb sandwich support structure and a robot. $\mathrm{A}\pm 3 ^{\circ}$ offset-focus feed trajectory is designed. Using the ABB IRB 6640 industrial robot instead of the traditional mechanical feed support bracket to move the feed on the trajectory. The on-site adjustment and compensation of the trajectory is achieved by a closed-loop adjustment system consisting of the robot and a laser tracker. After the adjustment, the positioning accuracy of the feed is guaranteed within 0.12 mm, which meets the electromagnetic design requirements. This new feed positioning device can achieve automatic offset-focus antenna test of multi-frequency in an unmanned environment.