29. The method of claim 26 wherein said predetermined plurality of received words is two received words.
26. A method for performing correlation of 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, comprising the following steps: forming a word segment sum over each of N word segments comprising said word, said segment sum comprising the sum over said word segment bits of products of each received word bit comprising said word segment with a corresponding reference word bit; and forming a digital correlator output signal at a rate equal to the word segment rate, said forming step including accumulating each segment sum 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.