GPS IIR-M and IIF: Payload Modernization

John A. Rajan and James Irvine

Abstract:	The GPS space segment has been instrumental in sustaining the signals for historical users and catering to emerging needs. The current generation GPS payloads, GPS IIR-M and IIF, to be deployed shortly, bring users several advances in technology and capabilities. ITT Research and Development (R&D) activities on High Power Amplifiers, Efficient Modulation Techniques, and Flexible Implementations led to several of the new features of IIR-M and IIF. These implementations use mature space qualified technologies and novel techniques to provide enhanced performance. This paper presents the results of our R&D efforts leading to the implementations in IIR-M and IIF navigation payloads. The modular, high efficiency architecture of GPS transmitters is presented. The architecture introduces GaAs technology for high power amplification and interplex modulation to provide M code to the users while minimizing modulation losses. The transmitter architecture provides a high degree of commonality between the L1 and L2 transmitters. A novel implementation for the interplex modulation that maximizes performance is presented. This modulator allows a high degree of miniaturization and commonality between code channels. Flexibility in waveform generation is also introduced in this architecture. The R&D effort led to miniaturized custom designs that enhanced performance. The payload implementation approach for IIR-M and IIF is also presented. The IIR-M upgrade leveraged our R&D efforts and minimized schedule and cost for deployment. The IIF transmitter implementation leveraged the IIR-M design, reducing the development time. These implementations enhance accuracy and provide onorbit flexibility.
Published in:	Proceedings of the 2005 National Technical Meeting of The Institute of Navigation January 24 - 26, 2005 The Catamaran Resort Hotel San Diego, CA
Pages:	508 - 514
Cite this article:	Rajan, John A., Irvine, James, "GPS IIR-M and IIF: Payload Modernization," Proceedings of the 2005 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2005, pp. 508-514.
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