合成孔徑雷達是一種微波遙測系統，其目的在於提供高解析的地表影像，尤其在固定的地表目標物與背景下，確實提供了很好的影像品質。然而在地表目標物為移動的情況之下，影像將變得模糊不清，且移動目標物與雷達間的都卜勒頻率與固定目標物與雷達間的都卜勒頻率相較之下變得複雜許多，而讓分析移動目標物的影像變得相當棘手與困難。 本研究主要利用時頻轉換方法，一種已廣泛應用於許多領域的結合時域與頻域的分析方法，來針對合成孔徑雷達移動目標物模擬影像作分析。主要利用從雷達訊號經處理後所得到的時頻平面圖，可得到移動目標物的都卜勒斜率與都卜勒中心頻率的偏移，再搭配推導出來的移動目標物都卜勒頻率公式，來作移動目標物的速度估算。 本實驗先從單一點移動目標物模擬影像起始，分別作不同方向與不同速度的估算，再加入多個點移動目標物的模擬影像，再用相同的估測方式估測一遍，以期達到可以使估測方法應用在不同情況的移動目標物模擬影像上，接著比較估測出來結果與當初設定的速度是否吻合。最後再利用真實影像來作估算，來驗證出此估測方法的實用性。 Synthetic aperture radar (SAR) is a kind of microwave remote sensing system. Its purpose lies in offering the high quality image of the earth's surface. But under the circumstances of moving targets, the image introduces smearing, and Doppler frequency between moving targets and radar becomes more complicated than it between stationary targets and radar. Then the analysis for imaging of moving targets is a difficult problem. This research is mainly to use joint time-frequency analysis (JTFA) that combines analysis in time domain and in frequency domain, to analyze SAR imaging of moving targets. It has been applied successfully to many areas of signal processing. By using JTFA, we can obtain the targets’ Doppler rate and Doppler centroid frequency from time-frequency plane figure of compressed radar signal. And combining to derive formula of targets’ Doppler frequency, we can estimate the velocity of moving targets. This study started from the estimation of velocity on simulated SAR images of single-target, followed by estimating velocity on simulated SAR images of multi-target, including moving targets move at different velocities and in different directions. Then we compare whether the estimation results are similar to the simulated velocity or not. Finally, we estimate it on real image to confirm the practicability of the analysis.
