into "squared" main beams are possible with both reverse and continuous phase tapers. However the penalty is an increased antenna size or a larger rectenna. (2) Adding suppressor rings to the antenna for reducing the first few sidelobe levels. Results indicate a 5 dB reduction in sidelobe levels at the expense of a loss in rectenna collection efficiency. Larger antennas or rectennas are again needed to retain the 88% rectenna collection efficiency. (3) Quadratic phase tapers. The analyses showed a decrease in on-axis power density (i.e., a squared beam) with a corresponding loss in beam transfer efficiency, dependent upon the amount of phase taper introduced. (4) Multiple antenna beams. The transmission of multiple beams from a single antenna is possible by spatially modulating the illumination function. Results for a simple two-beam SPS system were as predicted except for a small residual central lobe. Elimination of the central peak is a goal for future studies in this area. Summary: The characteristics and error parameters of the updated microwave transmission system may be summarized as follows: The relative importance of these electrical and mechanical tolerances upon scattered microwave power (extra power not incident upon the rectenna) is summarized in Figure 3.
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