Microwave diagnostic techniques are widely used in civil and industrial applications, especially because of their ability of penetrate inside dielectric materials. The simplest way to understand this phenomenon is to consider the propagation of a plane wave through a homogeneous medium. To this end, let us assume that a plane wave [equation (2.4.24)] is propagating along the z axis inside a material characterized by ε = ε′ − jε″ [equation (2.3.14)], and μ (real-valued). Thus
Accordingly, equation (2.4.24) can be rewritten as
For ideal dielectrics, α = 0; consequently, from equation (10.1.4) it results that |Ep(z)| = |E0| for any z; that is, the electromagnetic field is not attenuated. For low-loss scatterers (ε″ « ε′), we have
whereas for good conducting materials, for which the conduction effect ...