New quaternary sequences with optimal autocorrelation

We propose a new construction of quaternary sequences using the reverse Gray mapping of a pair of binary Sidel´nikov sequences. The proposed construction provides sequences of even period N with the maximum nontrivial auto-correlation magnitude, R_max = 2. For N ¿ 0 mod 4, the new quaternary sequences have the optimal R_max = 2 and are almost-balanced in contrast to the only earlier optimal construction S_j.