pattern nulls are deeper and wider than on-axis nulls, and require greater antenna tilt in favorable directions before the corresponding grating lobes reach higher intensities. 6. ANALYTICAL RESULTS The performances of the grating lobe peaks as a function of phase control to the subarray level and the power module level are shown in Fig. 14. The advantages of phase control at the power module level can be seen from this data, since one arc-minute tilt for subarray phase control and 3 arc-min for power module phasing give similar results. The peaks along the Y-axis represent the worst case condition. Using 0.01 mW/cm2 as a constraint for the maximum power density level, the allowable antenna tilt is approximately one arc-minute for subarray phase control and 6 arc-min for power module phase control. The best case grating lobes, or those with the lowest power density peaks, are also shown in Fig. 14. These lobes along the 45° axis are 20-40 dB or 2-4 orders of magnitude below the axial peaks. Other off-axis lobes in the 26.6°, 63.4°, etc., ground directions are also several orders of magnitude below on-axis peaks. Thus, for assessing environmental effects from grating lobes, only the axial lobes need to be considered. The direction of the antenna tilt is also a critical factor in determining which
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