陸基線性調頻連續波合成孔徑雷達系統近距離成像技術之研究

Near range condition for a Ground-Based LFM-CW SAR System

葉俊宏(Chun-Hung Yeh)

指導教授 ： 張中白

國立中央大學/太空及遙測研究中心/遙測科技碩士學位學程/碩士(2015年)

摘要

合成孔徑雷達(Synthetic Aperture Radar, SAR)是一個全天候主動微波成像雷達。它利用微波信號傳播到目標物計算其回波延遲的時間獲得垂直軌跡方向的分辨率，平行軌跡方向的分辨率則是利用載具與目標物之間的都卜勒效應來判定入標物間相對的空間關係。以線性調頻連續波(Linear frequency modulation continuous wave, LFM-CW)取代傳統脈衝波(Pulse)的雷達系統，有著體積小、重量輕、傳輸能量低的優勢，適合放置在地面和無人載具的短距離量測系統，但也因為其傳輸能量低的特性，探測距離也受到限制，適合用來做近距離量測。
理想的成像演算法是假設在距離遠大於速度和方位方向時間的情形之下，因為幾何條件和實驗情形，在衛載和空載的情形下能滿足此假設，但是在陸基合成孔徑雷達方面，其距離的變化大小會使假設條件無法成立，因實驗儀器和實驗場景的不同，量測的距離有可能是很小的，如果不考慮此情形，在成像演算法中方位方向壓縮的匹配濾波器(matching filter)會造成方位方向壓縮品質不好。因此為獲得高品質的雷達影像，必須考慮在觀測距離很小的情形之下，重新設計方位方向的濾波器，並且針對近距離量測的情形之下，重新對方位方向做壓縮，改善方位方向壓縮品質，並利用實驗室儀器得到雷達影像結果，並加入修正後的方位方向的濾波器來比較其成像的結果，發現修正後的濾波器能有效提高方位方向的解析度，得到較佳的雷達影像的結果。

關鍵字

合成孔徑雷達 ； 陸基 ； 近距離成像

並列摘要

Synthetic aperture radar (Synthetic Aperture Radar, SAR) is an all-weather active microwave imaging radar. It transmits microwave signals toward the target on a moving platform and records the returned signals. Conceptually, the resolution along the transmission path is determined by the echo path delay time while the resolution along the moving track is resolved by the Doppler effect between SAR platform and the target objects. Compared to pulse wave radar, LFM-CW (Linear Frequency Modulation Continuous Wave) radar has advantages of compact size, light weight, and low energy transfer, among others, which are suitable for ground and unmanned platforms requirements.
It is satisfy to the surmise for airborne and spaceborne, but it is not satisfy for ground-based system because of near range condition. If we are not considering the condition, the radar image result is not good because of match filter in azimuth direction. We have to consider near range condition and design the better azimuth matching filter because to get better image. The better matching azimuth can improve the image compression. We get the radar image in experiment and add the correction azimuth matching filter. Finally, We can get the better radar image from correction azimuth filter.

參考文獻

﹝13﹞王俊偉，「陸基LFM-CW合成孔徑雷達系統運動補償之研究」，國立中央大學，遙測科技碩士學位學程碩士論文，民國100年。

﹝4﹞A. Meta, J. J. M. de Wit, and P. Hoogeboom, “Development of a highresolution airborne millimeter wave FM-CW SAR”, in Proc. EURAD, pp. 209–212, Oct.2004.

﹝7﹞N. A. Cheadle, W. Lewis, H. Lee, and R. A. York, “Calibration of awide-band FMCW radar used for microwave SAR imaging”, in Proc.ASILOMAR Conf., pp. 141–144,May 1994.

﹝8﹞H. D. Griffiths,“Conceptual design of an ultra high resolution Wave synthetic aperture radar”, in Proc. IEEE Radar Conf., Ann Arbor, pp. 255–260,May 13–16, 1996.

﹝10﹞Z. H. Jiang, H. F. Kan, and J. W. Wan,“A Chirp Transform Algorithm for Processing Squint Mode FMCW SAR Data”, IEEE Geosciences And Remote Sense Letters, Vol. 4, No. 3,pp. 377-381,July 2007.