Synthetic aperture pulse-echo imaging with rectangular boundary arrays

Active imaging systems that estimate the reflectivity distribution of a remote scene often transmit pulses with short duration (wide bandwidth) in order to achieve range resolution, and employ two-dimensional (2-D) spatial arrays to achieve scanning and adequate resolution in the cross-range directions. Sparsely populated 2-D array geometries are very desirable in such applications so that system cost and complexity can be reduced to reasonable levels. A particular class of sparse 2-D arrays is called boundary arrays, and they have elements located only on the boundary of a convex region. Synthetic aperture signal processing techniques have recently been developed that allow boundary arrays to achieve the same imaging performance as more densely populated filled arrays. For example, a square boundary array with 4N elements can produce the same images as a filled square array with N-2 elements. The synthetic aperture techniques have been formulated in the context of far-field imaging with narrow-band signals, and they are based on the concept of the sum coarray for active imaging. In this paper, we demonstrate through computer simulations that the techniques are also very useful when wide-band pulses are used to image a finite-range scene. Thus, the recently introduced synthetic aperture techniques for boundary arrays can be applied in acoustical and microwave imaging applications.