Sequences with perfect correlation properties (i.e., vanishingsidelobes of their autocorrelation function) are applied in navigationalsystems, in synchronization, and for system measurement andidentification. Since only one periodic perfect binary sequence (lengthN=4) is known, on the one hand polyphase sequences with a larger phasealphabet, especially quadriphase sequences, and on the other handso-called complementary sets of sequences have been applied (Golay1961). Pairs of sequences are called aperiodic or periodic complementarysets (ACS or PCS) if the sum of their aperiodic or periodic respectivelyautocorrelation functions is a delta function. Complementary pairs ofbinary sequences cannot exist for all lengths. Therefore, sets ofternary sequences with the elements -1, 0 and 1 have been investigated.Since for technical reasons the number of zero-elements should be assmall as possible, ternary complementary sets are called optimum if noset with a smaller number of zero-elements exists. Ternary aperiodiccomplementary sets have been investigated in Garvish and Lempel (1994).In this paper, the construction of new optimum PCS and almost perfectquadriphase sequences is described
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