Flight Test Performance Assessment of DME (eDME)

Kuangmin Li, Wouter Pelgrum

Abstract:	Since its inception in 1952, the Distance Measuring Equipment (DME) has formed an essential part of aviation navigation. An extensive DME ground infrastructure is present globally, and most aircraft are outfitted with DME interrogator equipment. The transition to Performance Based Navigation (PBN) [1] increases the performance demands on the navigation systems, which warrants modernization of the existing DME/N system to enhanced DME or eDME. This paper presents the principle, execution, and analysis of a flight-test methodology to assess the performance potential of future eDME, by using current legacy DME transponder equipment and RF data recordings of both the transmitted and received DME signals. First, the collected DME flight test data is analyzed for received DME signal level, noise level, and legacy half-amplitude ranging performance. Secondly, the concept of carrier-phase DME is introduced. Tracking the carrier phase of the received DME pulses from a UTC time and frequency synchronized transponder allows ultra-accurate displacement measurements. The measured DME carrier phase tracking performance is compared with the theoretical carrier phase performance based on SNR. Next, several applications of DME carrier phase are introduced, implemented, and analyzed. Carrier-Smoothed Pulse pseudorange significantly reduces the noise and high-frequency multipath on the measured ranges. Pulse minus Carrier identifies the multipath on the pulse-ranging, and by observing the Pulse minus Carrier over at least one period of the slowest multipath fading, it effectively overbounds the multipath, thereby assuring the ranging performance. Finally, successive changes in DME carrier phase can be used to provide ultra-precise velocity, which enables significant performance improvements of collision avoidance applications and integrated DME-inertial systems.
Published in:	Proceedings of the 2012 International Technical Meeting of The Institute of Navigation January 30 - 1, 2012 Marriott Newport Beach Hotel & Spa Newport Beach, CA
Pages:	131 - 141
Cite this article:	Li, Kuangmin, Pelgrum, Wouter, "Flight Test Performance Assessment of DME (eDME)," Proceedings of the 2012 International Technical Meeting of The Institute of Navigation, Newport Beach, CA, January 2012, pp. 131-141.
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