Proposed Civil GPS Signal at 1176.45 MHz: In-Phase/Quadrature Codes at 10.23 MHz Chip Rate

A. J. Van Dierendonck, J. J. Spilker Jr.

Abstract:	The paper discusses a recommended signal structure for the new civil GPS signal that is to be centered at the frequency that we shall call L5 at 1176.45 MHz. In order to maximize the performance of this signal, it is important that it has clock rate of 10.23 MHz and be coherent with the other clocks in the GPS satellite, which are based on a 10.23 MHz master clock. The data rate on this signal is to be 50 bps as consistent with the existing data clocks on GPS or some multiple thereof. For this reason it is also important that the code period on this 10.23 MHz code be a multiple of 1023 to provide integer epoch relationships. It is also important to increase the code period on this GPS signal above the 1023 chip C/A code period (10- stage sequence generators) at the L1 frequency for the following reasons: improved cross-correlation and autocorrelation performance for improved multiple access, and improved interference protection. However, natural periods of codes generated with N-stage sequence generators equal 2 N - 1. This makes it impossible to establish a code period that is a multiple of 1023 without some sort of short-cycling. However, short cycling changes the desirable autocorrelation or cross-correlation properties of the codes. Fortunately, as will be shown in this paper, these changes are minimal, if not advantageous. This paper is extremely significant because the requirements and definition of the signal structure at this new signal frequency have recently been baselined to determine the impact on spacecraft design. Furthermore, the signal structure is used to determine how the new signal will coexist with other signals in nearby bands. This paper also presents other features of the proposed signal that depart significantly from the GPS signals at L1 that make it more robust.
Published in:	Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999) June 27 - 30, 1999 Royal Sonesta Hotel Cambridge, MA
Pages:	761 - 770
Cite this article:	Van Dierendonck, A. J., Spilker, J. J., Jr., "Proposed Civil GPS Signal at 1176.45 MHz: In-Phase/Quadrature Codes at 10.23 MHz Chip Rate," Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999), Cambridge, MA, June 1999, pp. 761-770.
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