Frequency adaptive digital filter for synchronization signal acquisition and synchronized event triggering

摘要

This paper shows that a digital filter consisting of a variable sample rate cascaded median, bandpass and predictor filter is able to provide a zero degree phase shift error between the input and output of a time varying flindamental frequency.The phase shift error is marginally affected by typical disturbances found on a utility or stand-alone network. This filter can be used in a wide range of applications in which synchronization signals or synchronized event triggering signals are requiredsuch as synchronous gating signal generators and discrete Fourier transforms. The frequency adaptive properties and magnitude versus frequency response of a variable sample rate cascaded third order median filter, 25th order Blackman filter and 15th order predictor filter have been experimentally verified. The output response of this filter when subjected to a wide range of line disturbances has also been simulated and exhibits acceptable characteristics.