Bachelor's degree in Physics from Wabash College and a Master's degree in Computer Science from The University of Texas at Austin. Mr. Renfro has been involved in development of systems for collecting and processing GPS data since 1979.
is a Senior Associate with Zeta Associates Inc. and currently is working GPS receiver performance and system engineering issues for the FAA GNSS Program. He previously was president of Grass Roots Enterprises Inc. and worked for the U.S. Government. He received his B.S. in physics from Norwich University. Mr. Swen D. Ericson has been involved with GPS and WAAS system engineering for the FAA at Zeta Associates since 2003. Prior to joining Zeta, he was a navigation system engineer at MITRE CAASD and a geodesist at Sidney B. Bowne and Son, LLP. He has a B.S. in civil engineering from the University of Miami and an M.S. in civil engineering from Purdue University.
A five-stage axial-flow compressor with all rotors operating with transonic relative inlet Mach numbers was designed as a research vehicle at the Lewis Research Center in 1952. The compressor was designed and tested as a component of a turbojet engine. This paper summarizes the research work done on this compressor including the aerodynamic design and detailed performance characteristics.
Signal generation in the GPS III satellites employs weighted voting to combine the baseband P(Y) signal with both components of the baseband L1C signal on the in-phase part of the L1 carrier. Weighted voting employs majority voting with pseudorandom time multiplexing of pure signals, producing a constantenvelope real-valued combination of the three biphase inputs with different useful received powers. Weighted voting introduces jitter into receivers' correlation functions, adding to jitter from noise and interference. This paper quantifies the effect of weighted voting on receiver input signal-to-noise ratio (SNR), then predicts the effect of weighted voting on carrier tracking by conventional, codeless, and semicodeless P(Y) receivers. Analysis and computer simulation results are supplemented by receiver measurements, providing conclusive evidence that degradation by weighted voting is evident only at high SNR, having an insignificant effect on receiver performance.
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