Phase difference detection

1. How does a phase detector work?
2. What are the different types of phase detector?
3. What is phase frequency detector?
4. What can be used as a phase detector in PLL?

How does a phase detector work?

A phase detector is a mixer-like circuit that puts out a signal that is proportional to the phase difference between two input signals of the same frequency. See Fig. 4.18. A phase shift is a time difference between two signals of the same frequency.

What are the different types of phase detector?

Two classes of phase detectors: (A) linear phase detector; (B) binary phase detector.

What is phase frequency detector?

PFD (Phase Frequency Detector) is a circuit that measures the phase and frequency difference between two signals, i.e. the signal that comes from the VCO and the reference signal. PFD has two outputs UP and DOWN which are signaled according to the phase and frequency difference of the input signals.

What can be used as a phase detector in PLL?

The more complex digital phase-frequency detectors usually have an output that allows a reliable indication of an out of lock condition. An XOR gate is often used for digital PLLs as an effective yet simple phase detector.