Noncoherent DTTLs for Symbol Synchronization

Noncoherent data-transition tracking loops (DTTLs) have been proposed for use as symbol synchronizers in digital communication receivers. [Communication- receiver subsystems that can perform their assigned functions in the absence of synchronization with the phases of their carrier signals (“carrier synchronization”) are denoted by the term “noncoherent,” while receiver subsystems that cannot function without carrier synchronization are said to be “coherent.”] The proposal applies, more specifically, to receivers of binary phaseshift- keying (BPSK) signals generated by directly phase-modulating binary nonreturn- to-zero (NRZ) data streams onto carrier signals having known frequencies but unknown phases. The proposed noncoherent DTTLs would be modified versions of traditional DTTLs, which are coherent.