Time Tracking Performance of GPS Type NRZ Direct Sequence Signals in the Presence of GPS Modernization Signals

J. K. Holmes, S. Raghavan, S. Lazar

Abstract:	A planned update of the block IIF GPS satellites includes the addition of wideband higher power military signals. This IOC considers the effects of multiple GPS signals interfering with the reception of the P code, along with the receiver thermal noise, as measured by the error in the P code tracking loop. The multiple interferers are modeled as a Gaussian random process with the same spectral density as the interfering signals. An assumption of the analysis is one P code signal is tracked, and is corrupted by a number of interfering signals (that would typically be in view) of one modulation type and thermal noise. The types of interfering signals that are considered in this IOC include either a P code or various types of split spectrum or binary offset carrier (BOC) signals, along with the usual receiver thermal noise. All the interfering signals are assumed to have long codes so that a random chip stream model is adequate. The code tracking loop chosen for analysis is a noncoherent I-Q baseband code loop with an early late time difference of one chip. The integration is over one bit time. The results contained in this IOC assume that the early late separation is one P code chip (d = 1 chip). The main result of this IOC establishes that for this code tracking loop type the effect of the interference is to add the one sided despread interference spectral density to the one sided noise spectral density at f = 0. A result of this analysis is that there is no frequency weighting of f 2 (such as found in a coherent code tracking loop using an ideal differentiator) for the effective noise spectral density, and that all the binary offset codes considered here yield less interference than that from P code to P code.
Published in:	Proceedings of the 1999 National Technical Meeting of The Institute of Navigation January 25 - 27, 1999 Catamaran Resort Hotel San Diego, CA
Pages:	627 - 636
Cite this article:	Holmes, J. K., Raghavan, S., Lazar, S., "Time Tracking Performance of GPS Type NRZ Direct Sequence Signals in the Presence of GPS Modernization Signals," Proceedings of the 1999 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1999, pp. 627-636.
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