A HSP condition T > 1 exists when the reductions by coupling (q., q) and detuning (fQ - fp are overcome by the field enhancement QE.. The resonance case leads for (7) to the reformulation At this point, let's briefly reiterate the train of thought that led to the array of variables introduced in equations (1) through (16). The first step is to find the incident power density S, which determines with (4) the exposure field strength E. Next, the coupling qi <_ 1 (6) into a chamber is specified and followed by an identification of inner surfaces that might support multiple reflections at or close to f . Then, the effective Q-factor of the resonance and the coupling q to the internal field strength E^ are estimated. For example, r = 10 km, L = 24 + 6 (tree shading) dB, S = 0.23 W/m^, E = 13 V/m; direct coupling (window), q. ~ 0.9; resonance between two metal partitions with Q ~ 4 at ff = f and a coupling factor of q = 0.05. It follows from (16) that there would be no HSP (T ~ 0.7). To obtain a more reliable assessment of a HSP, one needs to conduct a careful appraisal of field characteristics pertinent to specific reflector configurations in terms of their electromagnetic properties (reflection coefficient, resonance condition, dielectric constant, loss tangent, etc.). The identification of all arrangements which support enhanced or resonant fields based on available theoretical and experimental knowledge for the innumerable configurations is an impossible task. Real hot spot conditions can only be verified by "in situ" measurements in suspected areas. The following sections are intended as a fact-finding exercise to sketch properties of a 2.45 GHz field within habitable space in simplistic terms to bring out basic principles, while more detailed discussions of the points raised can be found in the references. 2. MICROWAVE COUPLING INTO AN ENCLOSURE The coupling (6) of microwave radiation involves factors that scale with wavelength. There are basically two ways to enter an enclosure. The first is to radiate through natural openings (e.g., windows, open access holes, cracks, etc.); the other is to penetrate through the surrounding walls. The interior energy SXi depends in a complicated manner on aperture size, polarization and angle-of-arrival for the incident wave, and on the electromagnetic properties
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