Method of processing a digital signal derived from an analog input signal of a gnss receiver, a gnss receiver base band circuit for carrying out the method and a gnss receiver

Abstract

An acquisition unit of a GNSS receiver base band circuit includes an integrator with a number of preprocessors where an incoming digital signal is mixed with different frequency signals to compensate at least in part for clock drift and Doppler shifts. The resulting digital signals are, after an accumulation step reducing sample frequency, integrated over an integration period extending over several basic intervals of the length of a basic sequence characteristic for a GNSS satellite, so that samples separated by a multiple of the basic interval are superposed. The resulting data sequence of 1,023 digital values is stored in one of two memories and then, in mixers, sequentially shifted by post-integration frequencies which are multiples of the inverse of the length of the basic interval. The pre-integration frequencies employed in the preprocessors deviate, with one possible exception, from the post-integration frequencies and are usually smaller.