Phase Frequency Detector
Can a digital phase detector be used as a frequency detector.
Phase detector versus Frequency detectors.Detectors are similar but not the same.
As name told us phase detectors are sensitive to the phase difference between two signals on input similary frequency detectors are sensitive to the frequency difference on its input.Practically phase detector are not sensitive to frequency if compare incoming signals from same source. Similary frequency detector are not sensitive to phase if incoming signals are with the same phases. In real life this events are very rear.Beacause of that both detectors are sensitive to each other characteristic of compared real signals on its input.
Practically phase detector can work as frequency detector but with very limitted range.If it is frequency difference big it will not work as frequency detector to help phase locking.Because of that it is necessary to have additional circuits as ramp generator or frequency detector to arrive close to locking range. More details you can find in books for example:"Microwave and Wireless Synthesizers Theory and Design" from Ulrich L. Rhode pages 288-323
GL XTASA