The principle to form a synthetic array is through transmitting pulses at index times p and receiving the echo signals at each sensor element position a p =[0,p ΔA,hog]T, where hog is the height overground and ΔA denotes the advance per ping of the imaging platform. A typical geometrical setup of a synthetic aperture imaging system operating in stripmap mode is depicted in Figure1, where the direction of wave propagation and the traveling direction of the imaging platform are called range, x, and along-track, y, respectively.