(1) Random Phase Error - A Gaussian distribution phase error with selected standard deviations wfll be applied to each subarray. These phase errors are due to noise in the phase lock loop reference in the subarray's RF receiver, phase shifts in the klystrons, errors in the calibrated path lengths of the phase reference distribution system, etc. The rectenna collection efficiency for 0°, 7°, 14°, and 20° phase errors are shown in Figure IV.A.2-14. There are no amplitude errors nor failures in these calculations. For a 5000 meter rectenna radius, the efficiency loss as compared to a 0° phase error system varies from 1% for a 7° error to 10% for a 20° error. The model configuration is specified to have a 10° error. (2) Amplitude Tolerance - A Gaussian distribution amplitude illumination error with selected standard deviations will be applied to each subarray. The amplitude errors are due to variations in klystron outputs, losses in the feeds and in the waveguides, etc. The rectenna collection efficiency for 0, + 1 dB, and + 2 dB amplitude errors are shown in Figure IV.A.2-T5. There are no phase errors or failures in the data. For a 5000 meter rectenna radius, the efficiency loss for a + 1 dB amplitude error (the model configuration) is only .5%. (3) Failure Rates - Random failure rates of selected percentages are now applied to the entire transmit array. The failures would be due to the failures in the 130,000 klystrons, the 7,850 RF receivers and phase control circuits, and possibly in DC power distribution system in the antenna. The rectenna collection efficiency for 0, 2%, 5%, and 10% random failure rates are shown in Figure IV.A.2-16 . There are no phase or amplitude errors for this data. Collection efficiency is very sensitive to random failures, with about a 2% drop in efficiency for each 1% failure rate. This corresponds to a loss in revenue over a 30-year life time of over $1 billion for each 1% failure rate. A reasonable goal is 2% failure rate for the model configuration. (4) Combined Phase Errors and Failure Rates - When there are both phase errors and failures in the antenna, the loss in rectenna collection efficiency is compounded. This data are given in Figure IV.A.2“17. for various combined phase error and failure rates. No amplitude errors are present. (5) System Performance with Specified Parameters - The model configuration has an error budget of 10° phase error, + 1 dB amplitude error and a 2% random failure rate. The rectenna collection efficiency for this configuration as shown in Figure IV.A.2-18 is 88% for a 5000 meter rectenna radius. This is the collection efficiency used when calculating the total DC output power. The power density at the rectenna for the baseline configuration is shown in Figure IV.A.2-19. The density varies from approximately 22 mw/cm? at the center of the rectenna to .9 mw/cm? at the edge.
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