Patent ID: 7308049

Claim:
An N-symbol noncoherent demodulator for a differential phase shift keyed (DPSK) type telecommunications signals, comprising: a) means for storing indications of quadrature components X(q) and Y(q) of N consecutive received symbols of the telecommunications signals, where q is an symbol index, and N is an integer equal to at least three; b) processing means for processing said indications according to VX i+1 ( k 1 , k 2 , . . . , k i )= VX i ( k 1 , k 2 , . . . , k i−1 )+ UX i+1 ( k 1 , k 2 , . . . , k i ) VY i+1 ( k 1 , k 2 , . . . , k i )= VY i ( k 1 , k 2 , . . . , k i−1 )+ UY i+1 ( k 1 , k 2 , . . . , k i ), where i is an iteration index with i=1,2, . . . , N−1, k i is an index of a phase differences between symbols with k i =1,2, . . . , M, with M being the number of permissable phase transitions, and where VX i+1 (k 1 , k 2 , . . . , k i ) and VY i+1 (k 1 , k 2 , . . . , k i ) are quadrature components at the i-th iteration, such that VX i =X(q−N+1), VY 1 =Y(q−N+1) are quadrature components of the first received symbol in the sequence of said N consecutive symbols, and UX i+1 (k 1 , k 2 , . . . , k i ) and UY i+1 (k 1 , k 2 , . . . , k i ) are transforms of the received symbol at the i-th step according to UX i+1 ( k 1 , k 2 , . . . , k i )= X ( q−N+i+ 1)cos[Δ( k 1 )+ . . . +Δ( k i )]+ Y ( q−N+i+ 1)sin[Δ( k 1 )+ . . . +Δ( k i )] UY i+1 ( k 1 , k 2 , . . . , k i )= Y ( q−N+i+ 1)cos[Δ( k 1 )+. . . +Δ( k i )]− X ( q−N+i+ 1)sin[Δ( k 1 )+. . . +Δ( k i )]; and c) decision means for determining a current symbol based on a phase difference Δ(k i ) corresponding to a maximum length of vectors defined by a relationship utilizing VX i+1 (k 1 , k 2 , . . . , k i ) and VY i+1 (k 1 , k 2 , . . . , k i ).