The theory of three-dimensional bifocal antennas

A solution is presented for the problem concerning the surfaces of two mirrors (two lenses) which transform two diverging spherical waves into two converging waves. A system of nonlinear partial differential equations with delay arguments is obtained for these surfaces. An analytical solution to the problem is given. It is shown that the initial condition (the surface of one mirror) is specified as an 'initial zone'. The freedom of the specification of the surface in the initial zone is limited by conditions of continuity and smoothness at its edges. Formulas are obtained for the mirror in the initial zone which satisfy the conditions of conjugation.