Figure 6-10. Array-Subarray Organization planar array antenna, and also shown is a quantized approximation to the Gaussian amplitude distribution, as may be the case for a practical implementation of an active array. Figures 6-11 and 6-12 indicate that five steps or more are needed to maintain efficiency, whereas Figures 6-13 and 6-14 show that only three steps are needed to hold down sidelobes. Effect of failure of a de power feeder (described in a previous section) is shown in Figure 6-15 to have a large but probably not an environmentally significant effect on sidelobes if the sidelobe levels are initially well below biological or environmental standards. 6.2 ARRAY TYPES The prime candidate for transmitting antenna implementation has been a circular, active, planar phased array, as illustrated in Figure 6-16. The reasons have been: a. High beam formation efficiency (95 percent) b. Passive dc-rf converter heat transfer to space c. Convenient phase control implementation d. Short rf distribution paths with low losses
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