This book is an essential resource for researchers involved in designing antennas and RCS calculations. It is also useful for students studying high frequency diffraction techniques. It contains basic original ideas of the Physical Theory of Diffraction (PTD), examples of its practical application, and its validation by the mathematical theory of diffraction. The derived analytic expressions are convenient for numerical calculations and clearly illustrate the physical structure of the scattered field. The text's key topics include: Theory of diffraction at black bodies introduces the Shadow Radiation, a fundamental component of the scattered field; RCS of finite bodies of revolution-cones, paraboloids, etc.; models of construction elements for aircraft and missiles; scheme for measurement of that part of a scattered field which is radiated by the diffraction (so-called nonuniform) currents induced on scattering objects; development of the parabolic equation method for investigation of edge-diffraction; and a new exact and asymptotic solutions in the strip diffraction problems, including scattering at an open resonator.