Effect of multipath and scattering on array gain of a large adaptive beam forming phased array

An adaptive antenna array system large enough to obtain angular resolving power comparable to common optical systems is called a radio camera. Following an adaptive beam forming procedure the beam is open-loop scanned to get the desired images. Multipath and scattering of the energy reradiated from the target induce phase-front distortions. A theory has been developed showing that the loss in array gain due to the scattered field can be described by a simple relationship involving only two quantities: the strength of the scattered field relative to the direct field and a spatial correlation function associated with the scattering process. The argument is the scanning angle. The array gain is . A series of experiments has been conducted to test the assumptions underlying the development of the theory, which appears to vindicate them. The theory and experiments are described. The theory is then used to determine the degradation in radio camera scanning performance for several important cases of interference caused by reflections.