A new type of lock detector for phase locked loops

Abstract

A new type of phase locked loop (PLL) lock detector is described. The new detector is substantially more robust in its ability to distinguish between phase lock and false lock than the classical phase quadrature lock detector. The theory is applied to a second-order loop with imperfect integrator, and it is shown that the classical phase quadrature lock detector is actually a first-order approximation of the new lock detector. The abilities of the new lock detector and the simple phase quadrature lock detector to differentiate between phase lock and false lock are compared and results are given.<>