Application of variable structure control techniques to a digital delay lock loop

Digital delay lock loops (DLLs) are widely used in digitally modulated communication systems. Their performance can be defined by the minimum time to achieve lock and there ability to maintain lock in high noise environments. While DLLs traditionally employ linear loop filters, this work investigates the application of variable structure (VS) control techniques to a digital DLL and examines its performance in the presence of white noise. A comparison is made with the performance attainable from a DLL with a VS and a linear loop filter with respect to the acheivable lock times and noise immunity.