This would represent the worst case as any random phase error held to within the limits presented below would represent better efficiencies. First, the phase across the aperture for a beam scan of 0g radians is given by For the case of 10 dB truncated Gaussian distribution the aperture distribution can be approximated by Using Equations 2.3-2 through 2.3-5, the beam scan, 0S, can be calculated for a given phase gradient, $, and the gain loss due to pointing error can be derived from P(a)). These calculations are shown in Table 2.3-3 along with percentage gain loss. As can be seen, a linear phase gradient of ±120° (0 - 40° across aperture) will cause a gain degradation resulting in a 1-percent decrease in efficiency. 2.3.4 Phase Control of MPTS Transmit Array The basic geometry of the SPS MW antenna as shown in Figure 2.3-19 consists of 7854 subarray panels within the aperture diameter of approximately

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