The power density incident in the fringes of the receiving site (see Appendix A for complete power density pattern) is given by (E is the peak electric field amplitude, ZQ = 377ft is the characteristic free space impedance), where L (dB) is the average power reduction factor as a function of the radial distance from the beam axis (Appendix A): The incident field might be further reduced by obstructions causing diffraction loss (e.g., trees located close to a housing structure). The diffraction edge for trees in full leaf was measured at 2.95 GHz to coincide with the physical height (LaGrone, 1977). In this case, the knife edge diffraction approximation can be used yielding additional 3 to 30 dB reductions in the effective power density S. 1.2. Formulation of the Hot Spot Problem* The electromagnetic field within a habitable structure is expressed via its electric field components interacting with dielectric and metallic material. The free space field distribution in chambers, such as rooms in a house, cockpit of a vehicle, cabin of an aircraft, etc., is to be investigated for local field 2 energy maxima (hot spots) E.. For a point with the internaUspace coordinates x, y, z, one can define and write a maximum power transmission coefficient to be (see equation 4) The objective of this study is to identify and, if possible, to quantify situations that might exhibit a field Hot Spot Problem (HSP) defined by *The term "hot spot" is used for a local electric field maximum; for the resulting thermal effect see equation (26).
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