Spatial Diversity Characteristics of Equatorial Scintillation. UHF and L-Band SATCOM Tests at Guam, July-December 1976

This report describes the results of space diversity tests conducted at Guam in the summer and fall of 1976 to evaluate the utility of this technique for mitigating the corrupting effects of equatorial scintillation on SATCOM links. Two wavelengths were employed for different systems evaluation one at UHF for Fleet SATCOM and one at L-Band for the Global Positioning System GPS. Down-link results at UHF showed that error rates approaching 50 percent can be completely eliminated by use of space diversity. Various statistical representations of data obtained three diversity spacings enabled thorough analysis required to investigate optimization of the diversity configuration. L-Band scintillation, though less intense than a UHF, did occur at levels that may affect the performance of the GPS. Estimates of reduced system margins at both the L1 and L2 frequencies used in the GPS are presented. Phase measurements at UHF are shown and a discussion relative to its effects on both systems is presented. Considered in the discussion is low-angle fading which is predicted to be of concern relative to the Indian Ocean GAPFILLER. Author