TWO-TONE DIVERSITY TO EXTEND THE RANGE OF DGPS RADIOBEACONS

Per Enge, Dave Young, and Bruce Butler

Peer Reviewed

Abstract:	To maximize the benefit-to-cost ratio, the coverage area of an individual differential GPS (DGPS) radiobeacon is generally maximized by radiating the greatest power com- mensurate with cochannel interference considerations. Typically, DGPS radiobeacons radiate a few watts and provide coverage for hundreds of kilometers over sea- water. At these ranges, the differential corrections are still valid and valuable. However at ranges over 100 km, the radiobeacon signal may reflect off the ionosphere (skywave) and destructively interfere with the desired signal, which follows the surface of the earth (ground- wave). Such interference can suppress the groundwave signal by 10 dB or more and is termed “fading.” This paper shows that only two frequencies, separated by a few thousand hertz, are needed to obviate this problematic fading. The paper presents field measure- ments that support this claim. Finally, it develops a coverage prediction method that accounts for the use of such two-tone diversity.
Published in:	NAVIGATION: Journal of the Institute of Navigation, Volume 45, Number 3
Pages:	161 - 172
Cite this article:	Enge, Per, Young, Dave, Butler, Bruce, "TWO-TONE DIVERSITY TO EXTEND THE RANGE OF DGPS RADIOBEACONS", NAVIGATION: Journal of The Institute of Navigation, Vol. 45, No. 3, Fall 1998, pp. 161-172.
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