form of phase control is needed to compensate for ionospheric and atmospheric changes, thermal deformation of structures, and phase variation in transmission lines and electronic system components. Figures 7-48 and 7-49 illustrate the two basic methods for array phase control. One or both of these methods, with refinements, will accomplish the very critical control of beam pointing and focus. Figure 7-48. Microwave power transmission system phase front control concepts. The simplest system of the two, the Command system (Fig. 7-48), utilizes a network of sensors on the ground receiving antenna to compare the received pattern to a computerized model. Changes in received pattern are interpreted by the ground computer as representing errors in the transmitted phase and are relayed via telemetric links to the solar power control station as a remedial command. This system obviously requires a sophisticated interpretive program relating ground antenna variations to the nature and location of changes required on the transmit antenna. The exact number and type of sensors required for such a system remain undefined, but they will probably be
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