Ramp-weighted correlation with oversampling

Abstract

A digital range correlator (50) for performing triangular ramp-weighted correlation relative to a reference word and providing an output data rate higher than the word rate. Two correlator channels (70, 80) are provided. Channel 70 provides a ramp-weighted segment sum over a word segment, with N word segments per L-bit word, wherein each received bit of a received word segment is multiplied by a corresponding ramp weight, and the corresponding product is in turn multiplied by the corresponding delayed reference word bit. The corresponding products over the word segment are accumulated to form a ramp-weighted word segment sum. Channel 80 provides a corresponding uniformly weighted word segment sum. The respective ramp-weighted and uniformly weighted word segment sums formed over the two preceding word segments are stored in a shift register. The ramp-weighted segment sums are scaled by +1 or -1 to represent the proper slope of the triangular weighting and accumulated. The uniformly-weighted segment sums are scaled by appropriate integers from 1 to N to represent the triangular weighting, and accumulated with the accumulated ramp-weighted scaled segment sums, and with appropriate normalization factors provide the correlator output signals. Digital Doppler or low pass filtering can be applied to improve the performance.