Fast acquisition of spread-spectrum signals by dynamically varying spacing of search bins

摘要

A Global Positioning System (GPS) receiver employs variable spacing of Doppler offset bins and code offset bins when acquiring a P(Y) code, to improve signal acquisition characteristics with respect to a search region having a plurality of Doppler offset bins and code offset bins. The receiver includes an acquisition module in which an input signal representative of a received P(Y) code is received and applied to a first programmable rate mixer. An output of the first programmable rate mixer is applied to a combiner, which selectively combines samples of the input signal based on a control input to dynamically determine the spacing of the code offset bins. An output of the combiner is normalized and applied to a correlation unit, which generates correlation measures of the received P(Y) code and a locally generated P(Y) code. A signal representative of the correlation measures is applied separately to each of a set of programmable rate mixers and mixed with separate mixing signals. The spacing of the Doppler offset bins is dynamically determined by controlling the rates of the mixing signals.