brief introduction: Introduction:Delay lines are used to insert a very precise delay into the path of a signal. A wide variety of delay lines are available. Some produce a fixed delay, often with multiple tap points, while others produce a delay that may be adjusted by an analog voltage or digital control word. Adjustable delay lines are a critical component of certain clock synchronization circuits such as a delay locked loop (DLL) or a synchronous mirror delay (SMD). The performance of an adjustable delay line is