In-Situ Calibration of an X-Band Antenna Array for Low-Angle Tracking with High-Resolution Direction-Finding Methods.

摘要

Presented in this report is an in-situ method to calibrate X-band antenna arrays designed to detect and track low-level missiles over water. These arrays are indispensable in ship defence, because they can operate in rainy and foggy conditions where atmospheric absorption is too high for the use of more accurate millimetre wave radars or optical devices. The method uses a set of array snapshots to construct a calibration matrix for the antenna array. It incorporates the compensations for unequal gain and phase responses at the array elements, antenna tilt, mutual coupling among the elements, the effect of local structures, and small errors in element positions. Simulation and experimental evaluations showed that the calibration: (a) improved the accuracy of target elevation angle estimates obtained with a high-resolution direction-finding method, (b) improved the resolution of target and image elevation angles, (c) suppressed a bias in elevation angle estimates, and (d) suppressed some anomalous tracks between the true target and image tracks. The calibration improves a ship's defence against low-level missiles.