that when the wires are thick and the interval is narrow, almost all of the microwave energy is received by the rectenna. Hoglinc rectenna [41 Figure 17 shows the hogline rectenna. This is considered to be a horn reflector antenna. The reflector and the horn are composed of the wires in a similar manner as the parabolic rectenna. The hoglinc rectenna receives the microwave beam from the SPS and passes the sunshine. We must determine which type of the rectenna should be chosen from the careful considerations of the performance, cost and ease of construction. Rectenna for the SPS strawman model The strawman model is an experimental version of the SPS system which has been discussed by the ISAS SPS working group. The SPS will be built in a low altitude (about 1000 km) equatorial orbit. The rectenna site is constructed in a developing country on the equator. Only when the SPS passes above the rectenna site, is the energy transmission experiment carried out. Since the experimental SPS orbits about the Earth from west to cast, the rectenna should have a broad beam in the east and west direction. The rectenna composed of the reflector and the CMSAs has a broad beam on the plane containing the focal line as mentioned previously. Then we should place the focal line in parallel with the east-west direction. The rectenna is sited in the jungle in the developing country. Figure 18 shows a concept of the rectenna site that could be constructed in Borneor, Indonesia. Figure 19 shows it on an uninhabited island. Many kinds of wild animals inhabit those areas as shown in figure 20. Because the rectenna proposed in this paper passes the sunshine, the experiment does not effect the ecology of the jungle. The animals will live safely below and around the rectenna. Inland Rectenna In the SPS system for practical use, the rectenna will be sited mainly in advanced countries. The rectenna is constructed cither inland or off-shore. From the point of view of energy transmission, the inland rectenna has the advantage over the off-shore one. Furthermore, the offshore rectenna is not preferable, since it must cope with salt damage, icing and sea birds [5], We may construct an artificial city under the rectenna. The diameter of the rectenna is about 10 km, and the urban area is about 64 m^ inside the rectenna. Moreover, we may construct an international airport with six runways around the rectenna as shown in figure 21. A great deal of electric power will provide us the livable environment in the city. Conclusions We have described the concept of a rectenna with a reflector and CMSAs. The rectenna receives microwave energy from the SPS with high efficiency and passes sunshine. Thus the rectenna docs not affect the environment and human society. The
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