Generalized Phase Comparators for Improved Phase-Locked Loop Acquisition

Phase-locked loops (PLL) with pulse-type (sawtooth) phase comparators find many applications in digital transmission systems. In this paper, the results available on the pull-in performance of the second-order PLL with sawtooth phase comparator are summarized. Then a generalized phase comparator, called a phase-and-frequency comparator, is shown to improve PLL acquisition performance significantly. Several circuit implementations are discussed in detail.