Concepts and Analysis of Translated GPS Range System Applications

Sultan Mahmood, Mohammed Miran, Burt Colt and Tanya Lambert

Abstract:	The Range Instrumentation System Program Office (RISPO) is developing the Translated GPS Range System (TGRS) for providing real-time and high accuracy post-mission Time Space and Positioning Information (TSPI) for a variety of DOD test and training range applications. The TGRS system is composed of an on-board Digital GPS Translator (DGT) and a ground-based or mobile GPS Translator Processor (GTP). The DGT re-transmits the S-band version of the raw L-band SV signal spectrum, along with digital telemetry (TM) stream. The GTP has the capability to track the SV signals and generate the state-vector information for mission analysis. The use of a DGT in lieu of a full-up GPS receiver offers an architecture for implementing critical advanced tracking requirements of the near future, with a small volume and low power on-board unit. Among these are rm&iple missile tracking and TSPI generation in a GPS jamming scenario. The implementation concepts and issues associated witb these applications are discussed and analyzed in this paper. The requirement to handle Ll/L2 raw GPS, high bandwidth TM, in a multiple missile tracking application created a challenging problem for TGRS tie to fresuency allocation restrictions. A solution for this using the patented PQPSK modulation scheme is studied, and feasible combinations of GPS and TM bandwidths vs. S-band transmit power are generated for system trade-offs. A variety of considerations such as transmit and receive antenna characteristics, DGT signal processing modes are included in the analysis. The performance of the TGRS system is dependent upon the user supplied L-band and S-band characteristics of the vehicle antenna. Parametric curves are provided to facilitate the users in generating realistic and reasonable antenna gain/phase requirements or assessing the impact of available hardware on system performance (acquisition time and TSPI accuracy). Presently, weapons are being developed with GPS navigation/guidance to operate in L-band jamming scenarios. Obviously, conventional GPS tracking methods cannot be used for evaluating the performance of these Anti-Jam GPS (AJGPS) equipped weapons on test ranges. The concept of an enhanced TGRS system is proposed and design issues are discussed. The feasibility of an AJ front-end in the GTP, that has a minimum size and design impact on the critical air-borne DGT is outlined.
Published in:	Proceedings of the 1998 National Technical Meeting of The Institute of Navigation January 21 - 23, 1998 Westin Long Beach Hotel Long Beach, CA
Pages:	703 - 711
Cite this article:	Mahmood, Sultan, Miran, Mohammed, Colt, Burt, Lambert, Tanya, "Concepts and Analysis of Translated GPS Range System Applications," Proceedings of the 1998 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 1998, pp. 703-711.
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