2 I R losses in the receiving elements and in the diodes. Approximately 7% of the incident energy is expected to be lost as heat. The expected power levels around the rectenna for reflected energy, leakage energy, harmonics, diffractions, and heat losses are summarized in figure 24. Microwave System Efficiency - The total microwave system efficiency from the DC power output at the rotary joint to the collected DC power output of the rectenna is 63%. A breakdown of the efficiencies of the microwave subsystems is given in figure 25. Phase Control System - The phase control system has an active, retro- directive array with a pilot beam reference for providing phase conjugation. Each subarray or possibly each power module (that portion of a subarray fed by one klystron tube), has its own RF receiver which processes the uplink pilot beam reference and inserts the proper phasing signal to form a single coherent beam at the ground rectenna. Tradeoff studies are now being conducted to determine if the phase conjugation should be at the subarray level or the power module level. Conjugation at the power module level improves main beam efficiency and microwave environmental effects, but increases costs and complexity. The Reference System includes: (1) phase lock loop around each power tube for phase stability and noise suppression. (2) double sideband, suppression carrier modulation which is symmetrical about the downlink power beam frequency f^, as shown below.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==