Eastern Europe may be moot for SPS design considerations, since many Americans are already exposed to microwaves at a level of 0.001 mW/cm2 due to radar, television signals, etc. [11], However, since people living near a rectenna will be exposed to microwaves continuously, a standard as strict as that for Eastern Europe may be desirable for residential areas. It is also likely that several different types of standards may be needed, e.g., residential, commercial, and industrial. Thus, the results presented here can serve as a zoning law study. The exclusion zone radii for n = 1 through 4, as well as the "ideal" case, were computed numerically for frequencies of 1 through 15 GHz. Results for safety thresholds of 0.01, 0.1, 1, 5, and 10 mW/cm2 are shown in Figures 4 through 8, respectively. (The 5 mW/cm2 standard is the U.S. limit on microwave oven leakage [ 14|.) It is seen in Figures 4 and 5 that for strict safety thresholds, there is a significant decrease in exclusion zone radius with increased beam taper. Interestingly enough, the "ideal" taper does not allow for as much of an exclusion zone decrease as the other tapers under consideration in Figure 4. The reason for this can be seen in Figure 3, which compares sidelobes for the n = 2 and "ideal" cases. Although these two cases have very similar main lobes, their sidelobe structures are quite different. 1'he n = 2 case has a large sidelobe at the approximate point where the "ideal" case has its first minimum, making it appear as though the "ideal" case has nearly no sidelobes. However, subsequent sidelobes are smaller for the n = 2 case. Figure 5 shows that at 0.1 mW/cnr, all of the tapers are roughly equally advanta-
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