Isolation of the field component formed by a given beam of rays at the aperture of a receiving antenna in an inhomogeneous environment

A generalization of the classical procedure for forming a receiving antenna beam in a homogeneous space to the case of an inhomogeneous medium is discussed. In free space, this procedure isolates the component of the registered field, which represents the contribution of a beam of parallel rays. In an inhomogeneous medium, the procedure should isolate the contribution of a beam of rays, which, as a rule, are not parallel. The generalization is carried out on the basis of the transition from the traditional representation of the registered field in the form of a superposition of plane waves to the coherent state expansion of the field borrowed from quantum mechanics. The general approach is illustrated using the example of the lobe formation of a vertical receiving antenna in an underwater acoustic waveguide.