A Novel Flexible Correlator Architecture for GNSS Receivers

Ville Eerola, Samuli Pietila, and Harri Valio

Abstract:	This paper describes a new architecture for the correlation processing inside a GNSS receiver. The group correlator (GC) is a code correlation device, which is optimized for parallel reception of multiple signals. It utilizes time- multiplexing to share some of the signal processing hardware amongst several independently operating channels. The GC can be used both in acquisition phase processing as well as in tracking phase processing. It can be used as the core processing block in a modern multi- system GNSS receiver due to its flexibility and efficiency. The group correlator typically computes a number of correlation results against a reference signal for a subset of the full code period. A second stage carrier mixer and a coherent integrator can be placed after the GC for further coherent integration of the correlation results. The GC performs the correlation operation in blocks of samples, where each block represents the length of the correlation performed inside the GC. By using multiple blocks of samples the full code period can be covered. Alternatively, multiple codes can be used with a smaller correlation range. One GC contains one or more replica code inputs, each of which is split into several parts of the same size. The GC will then perform partial cross- correlations between the input data and the replica parts. Coherent integration can extend the correlation length to cover the entire replica code duration or more, even though only a part of all possible code phase offsets would be covered. A complete GPS+Galileo receiver baseband with state-of- the-art performance based on the GC architecture is described and the parameter selection for its GC design is explained. A system simulator, which models the receiver, has been developed using SystemC and this has been used to evaluate the receiver operation in different scenarios. The performance of the designed receiver in some of the scenarios will also be shown.
Published in:	Proceedings of the 2007 National Technical Meeting of The Institute of Navigation January 22 - 24, 2007 The Catamaran Resort Hotel San Diego, CA
Pages:	681 - 691
Cite this article:	Eerola, Ville, Pietila, Samuli, Valio, Harri, "A Novel Flexible Correlator Architecture for GNSS Receivers," Proceedings of the 2007 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2007, pp. 681-691.
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