Flight Test of a Pseudo Ranging Signal Compatible with Existing Distance Measurement Equipment (DME) Ground Stations

Sherman Lo, Yu Hsuan Chen, Per Enge, Wouter Pelgrum, Kuangmin Li, George Weida, Achim Soelter

Peer Reviewed

Abstract:	Distance measuring equipment (DME) has been a cornerstone of aviation navigation since its development in the 1950s. Even today it is one of the most commonly used aviation navigation aid. However, the demands on aviation navigation systems will increase as the future airspace will need to accommodate the increased traffic, more precise operations and autonomous air vehicles. While GNSS will provide many of these improvements, terrestrial navigation systems will still play an important role in a robust aviation navigation infrastructure. Hence the FAA alternative positioning navigation and timing (APNT) program has been examining advanced concepts to improve on DME performance and capabilities while maintaining compatibility with existing equipment. One concept developed is a DME based pseudolite that position modulates existing DME pulse pairs. The pseudolite can operate alongside current DME operations and can be generated using the currently fielded DME transponders with an appliqué. The paper examines the implementation and performance of DME pseudolite appliqué on a DME transponder. It details the implementation of the appliqué on a currently available commercial DME/TACAN unit, the Moog MM-7000. The appliqué generates the pseudolite pulse pairs by interrogating the DME transponder in the same way an aircraft uses a DME. Rather than interrogating over-the-air, the system couples into the cable between the transponder and the antenna. Isolation components are added to prevent high power DME transmissions from damaging the circuitry of the applique while allowing the low power DME pseudolite signals to interrogate the DME transponder. To the DME transponder, the applique looks like another aircraft and does not have any priority over other transmissions. A preliminary design of the pseudolite signal was developed and implemented to provide synchronization, ranging, data and to account for losses due to having to operate with other aircraft interrogations. This design uses a software receiver to generate the interrogation and is tested on-air with the MM-7000. The performance of the unit was measured on the ground and on a test aircraft. The paper examines the synchronization and data performance of the transmitted DME pseudolite signal both in the air and on the ground. As we were operating on a test frequency, artificial traffic was injected to simulate a fully loaded DME. The paper compares the resulting performance to previously developed theoretical results.
Published in:	Proceedings of the 2016 International Technical Meeting of The Institute of Navigation January 25 - 28, 2016 Hyatt Regency Monterey Monterey, California
Pages:	98 - 109
Cite this article:	Lo, Sherman, Chen, Yu Hsuan, Enge, Per, Pelgrum, Wouter, Li, Kuangmin, Weida, George, Soelter, Achim, "Flight Test of a Pseudo Ranging Signal Compatible with Existing Distance Measurement Equipment (DME) Ground Stations," Proceedings of the 2016 International Technical Meeting of The Institute of Navigation, Monterey, California, January 2016, pp. 98-109. https://doi.org/10.33012/2016.13498
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