This paper presents a detection algorithm for micromotion targets, such as rotating antennas, in the synthetic aperture radar (SAR) geometry. It utilizes target's range cell migration characteristics, i.e. a micromotion target takes on a sine cure in the slowtime-range image, but with incontinuity or gaps when clutter (and part of target energy) is suppressed. Two-stage detection, including MTI and the extended Hough transform, is used to suppress clutter and to extract the sine curve. Quasi-real SAR data of Isleta Lake demonstrate high SNR gains and good detection performance.