都卜勒主動式雷達校正器利用混頻器在方位相像上面產生上下兩相對稱的頻移點 [1] ，更在2008年，改進了都卜勒主動式雷達校正器，使其產生的頻移點可達數十個[2]。但由於都卜勒主動式雷達校正器受限於每個頻移點之間的距離必須一樣，同時每個頻移點的輸出功率並不穩定。本研究希望可以利用FPGA來實現數位可調式都卜勒主動式雷達校正器，得以產生不同頻移距離的校正點。由於產生的頻移距離可隨自行調整，對於影像上的幾何校正有很大的幫助，同時藉由數位信號傳輸不易衰減的特性，讓頻移點的輸出功率較為穩定。此外，本研究也模擬將2010年發展出的數位可調式時間延遲主動式雷達校正器與本次研究的系統結合起來，希望能夠同時在方位方向以及斜距方向產生校正點，如此一來便可同時在方位方向以及斜距方向達成影像上的校正。 A tunable Doppler shift active radar calibrator (ARC) system has been developed in 2007 to produce two symmetric point targets along the SAR track [1]. It was further improved in order to generate much more frequency shift points up[2]. Because of the fixed frequency shifts and thus equal spacing on the image, it makes the site restricted in experiments, and the output power is not constant over these points. This study focuses on designing a digital Doppler shift in ARC system that produce artificial point targets at adjustable spacing and constant output power serving as control points for both geometric and radiometric calibrations. Furthermore, a combination of digital time delay and Doppler shift is simulated for feasibility study of a hybrid ARC system that generate point target on both azimuth and range direction.
