Returning to the picture of reflecting and interfering rays and disregarding the shape of the boundary, it follows that the resulting field amplitude enhancement (free space SWR, to be measured along three orthogonal axes of the interior space) can be significant only when repeated reflections with little loss occur. Figure 5 gives three examples of geometries that are in principle capable of sustaining multiple reflections. The point-to-point free space SWR of two interfering wave fronts can be made plausible with the simple phasor diagram depicted and evaluated in Table 5. The actual ratio within a chamber will be extremely dependent on position due to the complex variation of the reflected signals. Experimental results have shown spatial variations of electric field strength as great as + 40 dB in a room with bare metal surfaces (Donaldson et al., 1978). Depolarization is another effect which is counter to a HSP. The extent of depolarization of incident radiation in habitable space is a function of the complexity of the confinement. Obstacles will scatter omnidirectionally, thus mixing vertical and horizontal field components to become equal. Even oblique reflections from dielectric-coated metal surfaces can depolarize a wave train. For example, a lacquer paint (K ~ 10) with a thickness of 0.04 mm causes a decrease in the cross polarization isolation (19 GHz, 0 = 45°) between vertical and horizontal from 40 to 36 dB (Chu and Semplak, 1976). 3.3. Dielectric Properties of Typical Materials This section lists dielectric data of material that might be associated with habitable structures. The data summarized in Tables 6 to 9 were obtained from a survey of the sources referenced (VonHippel, 1954; Wells et al., 1975;
RkJQdWJsaXNoZXIy MTU5NjU0Mg==