A total breakdown of the phase control system, as would happen if the pilot beam from the ground was interrupted, is also shown in Figure IV.A.2-19. The power density is reduced to .003 mw/cm2, well below even the stringent USSR microwave limits. There should not be any health hazards if the phase control system fails completely. Two types of failures within the lateral DC power distribution system were investigated. Referring to the diagram below, switching failures in the lateral system near the center of the array (called Type I) and near the edge of the array (Type II)are shown. In each case a 5% loss in the number of radiating subarrays is assumed. The rectenna collection efficiency for these two types of failures are compared with a 5% random failure in Figure IV.A.2-20. As would be expected, the 5% discrete loss at the center of the array has the greatest loss in efficiency while the 5% loss at the edge has the minimum loss. The subarrays at the edge of the array have only 1/10 the radiated power of those in the center, and hence, do no appreciably affect the efficiency. IV.A.2(k) CONTINGENCY ISSUES Some studies have been done into the solutions of possible system problem areas. These include: (1) What can be done if the phase, amplitude, or failure rate requirements are too stringent, or the subarray misalignment tolerances cannot be met? One solution is to increase the size of the transmit array. The rectenna collection efficiency for 1.25 km antenna is compared to the 1 km, model antenna in Figure IV.A.2~21. Both curves have the same error budget, 10° phase error, + 1 dB amplitude error, and 2% failure rate. For the 10 dB taper curves, (1) and (2), the 1.25 km antenna gives 5-7% greater efficiency in the mainbeam and can compensate for greater errors or failure rates. Referring back to Section IV.A.2(i), the increase in transmit array cost for going to a 1.25 km diameter is $700X106, which is the equivalent in revenue cost ($522X106 per 1% collection efficiency) of 1.4% in collection efficiency. Thus, for a cost viewpoint, if the collection efficiency drops because of projected increases in the errors or failure rates, a larger transmit antenna may be justified.
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