Phase-locked loops: a control centric tutorial

Presents a tutorial on phase-locked loops from a control systems perspective. It starts with an introduction of the loop as a feedback control problem, with both the similarities and differences to traditional control problems. Chief among the differences is the necessary inclusion of two nonlinearities in the loop that are not parasitic, but essential to the loop's operation. Analysis methods, both linear and nonlinear are discussed. Then digital loops are discussed, followed by loop components and a cursory look at noise. Finally, the paper ends with a discussion of different applications of PLLs and their relatives.