Since this circuit is used at every subarray, the subarray center points are electrically normalized to show (})=$ constant across the entire array. This provides the conjugation circuit with the required reference phase. RETRODIRECTIVE BEAM CONTROL A retrodirective control circuit which compensates for pilot-generated beam shifts (without ionospheric effects) is the Chernoff circuit, with additional isolation added by (a) separating the pilot and power frequency paths, (b) using orthogonally polarized radiating elements; and (c) providing the remaining isolation in separate bandpass filters. The total required filter isolation is 70 dB, according to preliminary pilot system calculations. This pilot system is predicated on 100 dBw pilot power. The proposed implementation of this pilot system consists of a circular array of low to medium-gain elements placed at the periphery of the rectenna, on top of utility poles if necessary to avoid interference from the power collection and transmission system. The system provides vastly improved reliability over a single-dish, concentrated amplifier pilot system, and also provides such a wide power tube when the near-field beam enters the ionosphere that certain ionospheric effects will be mitigated. If ionospheric tests show that delay compensation through the ionosphere is required, a three-tone pilot system will be used. RF SIGNAL DISTRIBUTION SYSTEM The current baseline distribution system for the conjugated RF signal is the same for both solid-state concepts. Six "levels” of 4-way corporate divisions provide equiphase feeding to the 4,096 elements in each 5m x 5m subarray. The network is contained in one plane. The salient features of this distribution network are: weight of 0.67 million kilograms for the total array using UT-47M; 250 C temperature capability; approximately 7 dB ohmic loss (in addition to 3§dB splitting loss). All layers of coax are pressed together behind the ground-plane, and very little thermal resistance is presented to the heat being radiated rearward from the ground-plane in the end-mounted concept, and toward the ground-plane (from the solar cells) in the sandwich concept. The composite heat transfer will be established by the spacing between the ground plane and the solar cells in the case of the sandwich. An alternate approach uses stripline distribution underneath the groundplane. The advantage is better manufacturability but the ohmic loss is 20 dB higher, requiring more amplification.
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