Читать книгу Introduction To Modern Planar Transmission Lines - Anand K. Verma - Страница 224

All three cases of the angle of incidence apply to the TM‐polarized obliquely incident plane wave. For θ₁ > θ_c, the reflection and transmission coefficients of the TM‐polarization, given by equation (5.2.28) are reduced to

(5.3.9)

The electric and magnetic field components of the TM polarization, also the complex Poynting vector in the medium #2 under θ₁ > θ_c, could be obtained using equation (5.3.5), from equation (5.2.18). The results are summarized below:

(5.3.10)

The expression (5.3.9a) shows that there is a total reflection at the interface for θ₁ ≥ θ_c, without any transmission of power from the medium #1 to medium #2. The transmission coefficient shows the presence of the x‐directed evanescent field in the medium #2. Under such conditions, the interface acts as a perfect electrical conductor (PEC); so the interface surface of two media can act as the artificial electric conductor (AEC). However, there is an exponentially decaying field in the medium #2, and the interface supports the surface wave propagation along the interface at x = 0⁺ in the y‐direction. The real power carried in the y-direction along the surface is given by the real part of equation (5.3.10). The imaginary part of the Poynting vector shows the stored energy in the evanescent field. Figure (5.5c) shows the surface wave propagation in the y-direction that also occurs in the case of the obliquely incident TE‐polarized waves.

This subsection shows the existence of a surface wave at the interface of natural media. However, artificially engineered metasurfaces discussed in subsection (22.5.5) of chapter 2 has additional ability to control the surface wave in the desired manner, and also reradiate it as the leaky wave.