Tracking DDS in time and frequency metrology

It is possible to implement a real-time phasemeter/frequencymeter, by simply using a Direct Digital Synthesizer (DDS) in a Phase Locked Loop. Data written into the DDS to track the input is the output of this instrument. This scheme is compact, low noise, cheap, wide input range, real time and can be used in many applications both in RF and in Optical Frequency metrology.