fibers were selected for testing along with an injection laser diode for the emitter and an avalanche photodiode for the detector? Figure 1.0 shows the laser link configuration which was fabricated and tested prior to delivery to the JSC for future system testing with the Master Slave Returnable Timing System (MSRTS). The MSRTS provides electronic compensation for phase variations in the reference signal that are introduced by transmission path length differences and/or variations. A second example is the $100K contract with the Radio Corporation of America (RCA), awarded by the Marshall Spaceflight Center through Rockwell International. This task effectively continued an earlier investigation which RCA had initiated under contract to JSC for evaluation of potential solid state amplifier design requirements and characteristics. Several commercially available solid state devices were considered and some were experimentally evaluated. The Gallium Arsenide field effect transistors appear to be the most promising at the present time to achieve the high efficiency, high power (5 watts) required for SPS applications? The present task involves further analytical and experimental evaluations of both the solid state device and Its associated power amplifier circuitry. Computer modeling and simulation for synthesizing current and voltage waveforms under large signal operating conditions have been developed. These analytical techniques are used to define available tradeoffs for optimizing efficiency and output power for the solid state amplifier. Figure 2.0 shows some typical experimental results using off-the-shelf commercially available FETS. In one instance when optimized for maximum efficiency, a 71% power-added efficiency was achieved. However, tests of similar devices from the same manufacturer but rated for slightly less output power resulted in efficiencies of much less 60%). The incongruency in these results are under Intensive investigation in hopes to shed more light on the underlying causes of efficiency degradation. These experiments along with updated analytical models and computer simulations should provide the basis for device and circuit design parameter specifications to achieve the high power, high efficiency operation necessary. The other tasks noted previously each represent an advance In the technology base of one form or another and as a whole have added significantly to understanding the future satellite power system technological advances requI red. References: 1. Lindsay, Thomas A., "SPS Fiber Optic Link Assessment", Boeing Aerospace Company, January 31, 1980. 2. Belohoubek, E. F., et. al., "Analysis of S-Band Solid State Transmitters for the Solar Power Satellite", Final Report, RCA Laboratories, June 1, 1979.
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