Table 4. Power Attenuation Rate in Dielectric Material at 2.5 GHz Relative Dielectric Constant K 1 2 5 10 20 a in dB/cm Q 10‘3 0.002 0.003 0.005 0.008 0.010 c CD IO’2 0.024 0.034 0.052 0.075 0.10 CD SC 03 10 1 0.24 0.34 0.52 0.75 1.0 1— UI 1 2.2 3.0 4.7 6.8 9.1 UI O 10 10 14 21 31 43 —J Reflections - Upon striking the surface of a dielectric material, the incident field is split into two components of which one is reflected and the other passes through the medium. Specular reflections from a smooth surface cause the angle e of the reflected wave front to be equal to angle of incidence (Snell's law). For the HSP of interest, the amount of reflected energy is expressed by where p is the reflection coefficient. We learned that for metals p = 1, for practical purposes (Table 2). In case of dielectric material, p becomes a function of wave polarization, angle of incidence 6, and the properties K and D. Relatively simple expressions exist for the special case D ~ 0 (loss-free dielectric), where two different situations occur depending upon the orientation of the E^-vector with respect to the plane of incidence: (i) Ei is in the plane of incidence, (ii) Ei is perpendicular to the plane of incidence. For reflection on a horizontal surface, this means that for (i) the wave is horizontally and for (ii) vertically polarized. The respective reflection coefficients are (VonHippel, 1954)
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