GRATING LOBE CHARACTERISTICS The grating lobe peaks as described in the Reference System Report have maxima at 440-km intervals from the rectenna. The 440-km separation was predicated on phase conjugating at each 10.4-m x 10.4-m subarray, which was the smallest entity for phase control. Recent studies indicate that phase conjugation can be done at the power module (tube) level. Conjugation at the tube level improves main beam efficiency and reduces microwave environmental effects, but increases costs and complexity. The cost tradeoffs show that, if the cost per RF receiver and conjugating electronics is less than about $800.00, then phase control can economically be extended down to the tube level. Since the distance between maxima for the grating lobes is inversely proportional to the spacings between phase control receivers, an extension to the power tube level would reduce both the amplitude and the number of grating lobes. The grating lobe locations for the two conditions of phase controlling at the subarray and at the power tube levels are shown in Figure 2. The first FIGURE 2. Grating Lobe Maxima
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