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

A theory is developed to predict the effect of phase-front distortion due to multipath and scattering on the quality of the imaging process with a radio camera. The measure used is the loss in array gain due to the scattered field, as a function of scan angle from the direction of adaptive beam forming. The loss is described by a simple relationship involving two quantities: the strength of the scattered field relative to the direct field and a spatial correlation function associated with the scattering process. Experimental evidence lends support to the theory. The theory is applied to the following cases of interference caused by reflections: the fixed-point reflector and the specular reflector located in the array region, somewhere between the target and the array, and in the target region.