25. The correlator of claim 13 wherein said plurality of received words over which said correlator output signal is formed is two received words.
13. A digital correlator for correlating a succession of received digital words in a serial bit stream with a reference digital word of bit length L having a reference word period, the correlator comprising: means for providing a set of ramp weights W(k), where k=1 to L/N, where N is a number of word segments comprising said received digital word, each word segment having L/N bits; ramp-weighting summing means for forming a ramp-weighted sum over each of said N word segments, said summing means comprising means for accumulating the respective sums of a product of a reference word bit with a product of a corresponding received bit comprising said segment with a ramp weight W(k) for each bit comprising said word segment; uniformly-weighting summing means for forming a uniformly-weighted sum over each of said N word segments, said summing means comprising means for accumulating the respective sums of a product of a reference word bit with a corresponding received word bit for each bit comprising said word segment; and means for forming a digital correlator output signal at a rate equal to the word segment rate, each output signal comprising a triangular-weighted sum of scaled versions of said ramp-weighted sums and said uniformly-weighted sums over a plurality of preceding word segments covering a predetermined plurality of received words, whereby degradation of said correlator performance caused by Doppler shift modulation on said received signals is reduced.