Digital Translator Design Wades

Mark A. Sturza, Alison K. Brown

Abstract:	GPS Translators are currently used on a number of programs for instrumenting missile tests. Translators allow high-dynamic vehicles to be tracked through accelerations up to 50 g while minimizing the size, weight, and cost of the expendable flight hardware. The analog nature of existing Translators prevents encryption of the downhnk signal and requires highly complex and costly ground stations. The size and weight of the current Translators prohibit their use on many applications. The current Ballistic Missile Translator (BMT) is 40 cubic inches and weighs 5 lbs. Digital Translators can take advantage of state-of-the-art digital devices to functionally simplify the GPS signal translation. The resulting digital downlink signal is readably encryptable and supports the downhnk of inertial and/or telemetry data in addition to the digitized spectrum. Various methodologies to digitixe the Translator L-band input spectrum and to modulate the Translator S-band output signal have been investigated. Digitization of the L-band spectrum involves bandlimiting, sampling, and quantization. Each of these operations can result in correlation loss. Correlation loss trades have been performed to select digitization parameters for optimal perfOrmanCe. The digital Translator approach provides a variety of S- band modulation options. The bit stream resulting from digitization of the L-band spectrum can be used to phase, frequency, amplitude, or pulse modulate an S-band carrier to form the output signal. Each of these modulation options has been investigated. various options for integrating inertial and/or telemetry data into the S-band downlink signal have also been investigated.The low cost, small size, and light weight achievable with digital translators make them ideal for use in a wide variety of military and co mmercial tracking applications. These include DOD missile tracking programs, radiosondes, small projectiles such as Brilliant Pebbles, and space-based systems.
Published in:	Proceedings of the 5th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1992) September 16 - 18, 1992 Albuquerque, NM
Pages:	687 - 695
Cite this article:	Sturza, Mark A., Brown, Alison K., "Digital Translator Design Wades," Proceedings of the 5th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1992), Albuquerque, NM, September 1992, pp. 687-695.
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