Fundamentals of the Physical Theory of Diffraction, 2nd Edition

Conclusion

The PTD developed in this book clarifies scattering physics. Via the shadow radiation, it elucidates the nature of Fresnel diffraction and forward scattering as well as the optical theorem. It also establishes the diffraction limit for reduction of the total power scattered by large (compared to the wavelength) objects covered by absorbing materials. This theory shows that even with the application of perfectly absorbing coatings on perfectly reflecting objects, their total scattered power can be reduced solely by a factor of 2. This means that against bistatic sonar and radar, it is impossible to mask the scattering object completely by any absorbing materials (Ufimtsev, 1996). A recent cloaking idea to construct invisible objects is discussed briefly in Section 1.4.3. It consists of the development of nonabsorbing coatings with special tensor permittivity and permeability which would allow the incident wave to bend an object smoothly without reflection and without shadow radiation.

As a source-based theory, PTD allows the calculation of contributions to the scattered field which are generated by individual elements of the scattering surface. Such data are valuable in the design of antennas and of objects with given characteristics of radiation and scattering. PTD is a flexible theory amenable to further development and generalization. In combination with other analytic and numerical approaches, it can be used to create efficient hybrid techniques for the solution ...