航空雷達之運動補償

Abstract

由於航空雷達在飛機上受到載具飛機在空中的運動，大氣亂流的干擾，以及飛機結構的振動，造成雷達運動軌跡的偏差。因此雷達必須對其飛機運動的變化，去修正雷達掃瞄行徑軌跡、改變參考訊號的相位，和消除相位誤差。本論文主旨在於如何修改雷達的運動方位以補嘗掃瞄路徑的偏移，以解決影象的失焦及掃瞄目標位置的準確性，並且防止解析度的減少。而其主要的工作有三：第一、了解合成孔鏡雷達成像的基本原理。第二、以六軸平臺作為飛機的載具，再將兩軸的gimbals機構作為雷達兩軸機構，然後置於六軸平臺上，用以作為航空雷達架於飛航工具之運動模擬。第三、在訊號處理上，模擬phase gradient autofocus (PGA) 方法來解決高次項相位誤差造成的影像失真。

The antenna deviates from the ideal trajectory because of pilot-induced maneuvers, atmospheric gusts acting on the aircraft, and structural vibrations within the aircraft. We have to compensate the motion uncertainty of aircraft by correcting the motion deviation of radar, update the phase of reference signal, and eliminate phase error. The main idea of my thesis is how to compensate the motion error of aircraft, correct phase error, which smears radar image and mispoint the synthetic aperture. Moreover, preventing degradation of resolution. So there are three important steps: first, to study and understand the fundamental imagery approach of SAR. Second, in order to simulate the airborne radar system on the aircraft, we will use six-axis Steword platform for aircraft, three-axis gimbals for radar gimbals, and set up the two-axis gimbals on the six-axis platform. The airborne radar system is simulated with the motion platform. Third, in terms of signal processing, using PGA algorithm to eliminate high order phase error which defocus the radar image.