through a proportional increase in antenna or rectenna diameter, or a decrease in wavelength. A second physical constraint on microwave transmission is the far-field beam formation requirement: antenna radius V2 [wavelength x transmission range]1'2 Antenna beams cannot be concentrated onto smaller sized rectennas without incurring near field degradations. In the near field, considerable energy is lost to sidelobe scattering and asymmetrical intensity distributions across the rectenna. Several sizing and frequency configurations for nuclear satellite power transmission have been evaluated using a computer program designed to model the SPS phased array. Antenna configurations are given a standard error allowance (o-) of 10° RMS phase error and ±.l dB amplitude error for the power tubes, and utilize an optimal antenna taper. An 85% power collection efficiency has been chosen for rectenna sizing; larger rectennas begin to collect beam null regions and would show very little efficiency gain for large area expenditures. In the first case, sizing configurations for a transmission frequency of 5.8 GHz are examined. The desired transmission ranges and corresponding required rectenna diameters (for 85% power collection) are shown in Fig. 11 for antennas of 5, 10, 20, and 30 m diameter. At 5.8 GHz, small antennas (5 m or 10 m diameter) are appropriate only for 1-2 km ranges, 20 m antennas work for 5-10 km ranges, and 30 m or larger antennas are suitable for greater distances. To transmit a range of 5 km, the small antennas require
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