Nonlinear spectral problem in synthesis problems of plane antenna arrays

A nonlinear synthesis problem of plane equidistant antennas array by the given requirements to amplitude directivity pattern is investigated. For such problems non-uniqueness and branching of the solutions dependent on physical parameters of array is characteristic. Finding the set of branching points of the solutions is a nonlinear two-parametric spectral problem. The method of finding the branching lines of the solutions and numerical algorithms of solving the optimal synthesized amplitude directivity patterns is stated.