difference between tracking , capturin and lockin range PLL

[ysenthilece]

difference between tracking , capturin and lockin range PLL

and how to find these for a given PLL

 

[VVV]

Re: difference between tracking , capturin and lockin range

The capture range or lock-in range is the frequency range for which the PLL, initially in an unlocked state, can lock onto the incoming signal.

Basically, the PLL's VCO is running at frequency fo and it will lock onto the input signal if the incoming signal's frequency is f0±Δfc. So the capture range is 2Δfc.

Once the PLL has locked, it can "follow" the input signal over a generally wider range than the capture range. This is known as the tracking range.

These parameters result from the design of the low-pass filter of the PLL.
For a practical circuit, you can just apply a varying signal at the input and check when the PLL locks and when it stops following. For example, to check the capture range, apply an input frequency that is low enough for the PLL not to lock. Then increase the input frequency until the PLL locks. Then repeat with a higher frequency and check when the PLL locks, by reducing the input frequency. Now you found the capture range.
For the tracking range, make sure the PLL is locked first and then vary the frequency both lower and higher, each time until the PLL unlocks. The difference between the two frequencies is the tracking range.