Practical and Theoretical Tradeoffs of Active Parallel Correlator and Passive Matched Filter Acquisition Implementations

P. A. Dafesh and J. K. Holmes

Abstract:	Over the years, a number of acquisition implementations involving active-parallel correlator (APC) [1-4] or passive-matched filter (PMF) [5-7] search implementations have been proposed. These implementations apply to acquisition of the GPS precision (P)-code and the course acquisition (C/A) code signals [1], as well as the new modernized GPS signals [1,3,4,7]. While many receiver search schemes employ an active parallel search implementation, there has been recent interest in PMF search implementations due to their theoretically fast search rates. This work studies the practical and theoretical differences between the acquisition performance of the APC and the PMF acquisition search implementations. Without loss of generality, results are discussed in terms of the P-code signal acquisition problem. Generalizations to the Military (M)-code signal and the C/A-code signal are also reviewed. The performance of both APC and PMF search implementations are computed as a function of interference to signal power ratio under the assumption that each implementation employs a parallel frequency search using a zero padded Fast Fourier Transform (FFT), for matched spectral sources interference. The acquisition time performance of these implementations are also described as a function of computational rate in operations per second, code rate, theoretical implementation losses, and interference level for a fixed set of initial conditions. The receiver complexity (computational load) of C/A, P and M-code are also compared for a fixed acquisitiontime performance and Interference to Signal power (I/S) ratio. Tradeoffs between computational complexity and acquisition performance are reviewed for cases of both low and high I/S levels. For a fixed receiver computational rate and moderate to large frequency uncertainties, it is shown that the performance of the APC search implementation is generally superior to that of the PMF approach. Exceptions are discussed in terms of limiting conditions of integration period, frequency uncertainty and computational rate assumed for either implementation.
Published in:	Proceedings of the IAIN World Congress and the 56th Annual Meeting of The Institute of Navigation (2000) June 26 - 28, 2000 The Catamaran Resort Hotel San Diego, CA
Pages:	352 - 367
Cite this article:	Dafesh, P. A., Holmes, J. K., "Practical and Theoretical Tradeoffs of Active Parallel Correlator and Passive Matched Filter Acquisition Implementations," Proceedings of the IAIN World Congress and the 56th Annual Meeting of The Institute of Navigation (2000), San Diego, CA, June 2000, pp. 352-367.
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