2. Resonance absorbers are much thinner than the broad-band type by taking advantage of the coherency in radiation. They are well suited for SPS applications. Reflections at the surface are suppressed by canceling them with reflections from the conducting base when the thickness £ = xq/4. Under this type fall the Salisbury Screen absorbers (used in radar applications) where the remaining front-face reflections are reduced by a resistive layer. Covering metallic surfaces results in a typical reduction in reflectivity by 25 dB (Emerson, 1973). 3. Surface absorbers are designed to attenuate field-induced surface currents. They are not as effective as the other two types since £ << , but they are easy to apply as spray or paint. 6.3. Mode Scrambler Uniformity can be achieved by perturbing the field both in time and space with a moving reflector (rotating vane, oscillating metal sheet, etc.) within the chamber. Such a mode stirrer tunes the enclosure through all possible resonant modes at the frequency f . The electric field will pass through the possible maxima EQ for each sequentially excited mode, thus essentially "smoothing" any spatial field distribution. If feasible, another suggestion for mitigative measures of field hot spots deals with the possibility of randomly frequency-modulating the SPS microwave carrier being the electronic equivalent to a mode scrambler. 7. CONCLUSIONS Incident SPS microwave energy which falls outside the rectenna area upon habitable structures will penetrate their chambers via aperture and "diffusion" coupling. The concentration into field "hot spots" (i.e., exceeding the incident level) by focusing, caustic surfaces or by multiple reflection mechanisms is, in principle, possible; however, dielectric losses and scattering from odd-shaped obstacles, normally part of habitable space, should clutter any spatial field pattern. The foregoing treatment dealt in an elementary way with coupling of field energy into an enclosure and its possible spatial redistribution in standing wave or resonance fields. It should be emphasized that habitable space presents a poorly defined EM problem and that the whole subject has not received much attention. We attribute the lack of theoretical field analyses to the overwhelming complexity of the enclosure-contents configurations. The presence of
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