shown in Fig. 11. The digital signal is multiplied at each radiating module location by a factor proportional to its physical distance from the center of the array. The multiplied digital signal is then used to activate a digital phase shifter (see Fig. 3) in each radiating module location to add or subtract a phase angle to the reference microwave signal which has been adjusted at all radiating module locations to bore sight the phased array antenna on zenith with no digital signals in the row and column matrix. The manner in which the bore sighting is done without the need for a target is described in Ref. 3. With this arrangement of controlling the individual phasing of the radiating modules from two digital signals, it is immediately apparent that the value of these digital signals can be varied slightly to compensate either for an expansion and contraction of the array, for a first order correction for physical warping or focusing of the array, and even for a change in frequency of the reference microwave source. CONCLUSIONS The update on the design of the solar power transmitter has been largely derived from the solution of problems encountered in the conceptual design of a ground- based, electronically steerable array, for supplying power to an airship or airplane circling at a high altitude in Earth’s atmosphere. In essence, the whole ground array becomes the model for one of the subarrays in the solar power satellite transmitting antenna. The update has been effected without compromising any of the features of high efficiency, long life, low noise level, minimal associated power conditioning, and low specific mass and cost that were established during the DOE/NASA study of the SPS (3,4). REFERENCES 1. The Final Proceedings of the Solar Power Satellite Program Review DOE/NASA Satellite Power System Concept Development and Evaluation Program. July, 1980, Conference: 800491. 2. W.C. Brown, Satellite Power System (SPS) Magnetron Tube Assessment Study, NASA Contractor Report 3383, February, 1981, Contract NAS8-33157. 3. W.C. Brown, Design Study for a Ground Microwave Power Transmission Study for Use With a High-Altitude Powered Platform, NASA Contractor Report 168344, June, 1983. Raytheon Report PT-6052, May, 1982, Contract No. NAS6-3200. 4. W.C. Brown, Microwave Beamed Power Technology Improvement. Final Report JPL Contract No. 955104, Raytheon Report PT-5613, May 15, 1960.
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