GPS Block IIF Civilian Dual Frequency Design

Michael Shaw, Mohan Ananda, Paul Massatt, Prem Munjal, Srini Raghaven, and K. T. Woo

Abstract:	The GPS Joint Program Office is acquiring Block IIF satellites; civilian dual frequency capability is a preplanned option. This paper deals with the incorporation of a dual frequency C/A code capability in the Block IIR satellite for civilian users. The design and analysis presented here are also expected to apply to the future Block IIF satellites. Weight and power impact on the satellite are described. Analyses have shown that weight increase due to suggested modification to implement civilian dual frequency signals is about 1.3 percent, and therefore a rough order of magnitude of the cost associated with the changes would also be about 1.3 percent of the satellite cost provided that the modifications are incorporated in the initial design of the satellite payload. Issues are addressed regarding selection of the second civilian frequency by examining interference concerns due to presence of other signals. A spectrum of frequencies has been studied and this paper provides a number of available frequencies from which a final selection could be made by considering the factors affecting the various Government agencies. Dual frequency benefits are addressed for civil GPS applica- tions such as aviation, land transportation, marine navigation, offshore applications, precision farming, surveying, forestry, Intelligent Vehicle Highway Systems, and railroad track measurements. To illustrate the potential enhancement provided by dual frequency signals analyses have been performed to compare WAAS CAT-I precision approach availability for single and dual frequency cases under different satellite scenarios and error correction bounds. Discussion is also included about the potential of dual frequency to facilitate extension of WAAS operations globally and interoperability of WAAS with other service provider systems. Although availability enhancements are addressed in this paper, cost benefits to the program have not been analyzed. These cost benefit studies are currently underway by the United States Department of Transportation (DOT). Implementation of dual frequency is not considered necessary to meet end-state WAAS CAT-I requirements, but is only being considered for its value to enhance service to FAA WAAS and other civil users and the potential it has for reducing future costs.
Published in:	Proceedings of the 1996 National Technical Meeting of The Institute of Navigation January 22 - 24, 1996 Loews Santa Monica Hotel Santa Monica, CA
Pages:	871 - 887
Cite this article:	Shaw, Michael, Ananda, Mohan, Massatt, Paul, Munjal, Prem, Raghaven, Srini, Woo, K. T., "GPS Block IIF Civilian Dual Frequency Design," Proceedings of the 1996 National Technical Meeting of The Institute of Navigation, Santa Monica, CA, January 1996, pp. 871-887.
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