摘要: Ramanujan sums have in the past been used to represent arithmetic sequences. It is shown here that for finite duration (FIR) sequences with length N, traditional representation not suitable. Two new types of Ramanujan-sum expansions are proposed FIR case, each offering an integer basis. One these particularly suited identify periodicities sequence. This fact expresses any sequence as a sum orthogonal hidden periodicity corresponding divisor N.