In this work, we consider a radar system where the antenna elements are arbitrarily distributed in space with separations of several hundred wavelengths. We call such a radar system a distributed aperture radar system. We assume that the system is operating in a multipathing environment, such as an urban area. We present methods for i) rejecting clutter in transmit processing via preconditioning, ii) designing waveforms to image orthogonal components of target reflectivity, iii) forming target reflection images via matched filtering for sparse distributed aperture arrays. This work generalizes the monostatic radar waveform design method for range-Doppler imaging developed in [1,2] to distributed aperture radar systems. Our approach utilizes Gram-Schmidt orthogonalization (GSO) procedure. The designed waveforms also lead to a filtered-backprojection type reconstruction of the reflectivity function which can be efficiently implemented in a parallel fashion. Although our discussion is focused on radar, the ideas and methods presented in the chapter are applicable to other pulse-echo imaging systems, including sonar, ultrasound and medical microwave imaging. The rest of the chapter is organized as follows. In Section 2, we present a physics based model for scattered field in multi-pathing environment. In Section 3, we present the measurement model for distributed aperture arrays. In Section 4, we derive the preconditioner for clutter rejection. In Section 4, we discuss our waveform design criterion and present our image reconstruction method. We then apply these waveform design and image reconstruction techniques to single transmitterreceiver pair and next apply to distributed aperture arrays. Section 6 concludes our discussion.

Inspec keywords: radar imaging; radar transmitters; radar clutter; radar antennas; radar receivers; image reconstruction; matched filters

Other keywords: sparse distributed aperture arrays; target reflectivity; image formation; image orthogonal components; distributed apertures; matched filtering; distributed aperture radar systems; range-Doppler imaging; multipathing environment; clutter rejection; target reflection images; antenna elements; image reconstruction techniques; Gram-Schmidt orthogonalization; single transmitter-receiver pair; physics based model; reflectivity function; filtered-backprojection type reconstruction; radar clutter; sonar imaging; pulse-echo imaging systems; waveform design; distributed aperture arrays; distributed aperture radar system; monostatic radar waveform design method; medical microwave imaging; ultrasound imaging

Subjects: Filtering methods in signal processing; Optical, image and video signal processing; Radar equipment, systems and applications