Requirements for the tuning linearity of VCO

[meseasky]

Hey guys

My question is about the tuning linearity of a VCO, in the application of PLLs or frequency synthesizers, are there clear quantitative requirements on the tuning linearity of VCO, like the requirements on phase noise

The more linear the better, sure, but that is too ambiguous...

I have done some "google work", some articles say the tuning linearity of a VCO is not so crucial in PLLs as in FM application in Microwave domain. I also find that tuning linearity is specified in the datasheets of many VCOs, but why it is specified? who cares about it ?????

Well, I got really confused here! Help me and thanks in advance.

 

[strabush]

Re: A Question on VCO

One clear requirement is the PLL loop stability.
If the VCO gain changes, so will the PLL loop gain.
Simulation of the PLL control loop will show the dynamics of the loop at different frequencies and most important its phase margin.

 

[lianming1]

A Question on VCO

yes, the tuning linearity of vco is very important here