The refernce frequency and the loopbandwith

Status
Not open for further replies.
J

John Xu

Member level 3
Joined
Jul 22, 2005
Messages
59
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
1,938
I have a question on the PLL. In some papers about PLL design, it is asserted that the reference frequency and the loopbandwith should have at least one decade difference to guarantee the stability. Can any one tell me why?

Thanks in advance!!!
 

John Xu said:
I have a question on the PLL. In some papers about PLL design, it is asserted that the reference frequency and the loopbandwith should have at least one decade difference to guarantee the stability. Can any one tell me why?

Thanks in advance!!!
Click to expand...

i think the word stabiltiy is not accurate. while the important reason for taking Loop bandwidth = Fref/10 (as an assumption) is to have better immuning for the refrunce spurs (more attenuation). so you will find that the design is matter of trade-offs as when deacresing the Loop BW will make the Loop slower while the refrunce spurs will be more attenuated.

Best Regards
 

    J

    John Xu

    Points: 2
    Helpful Answer Positive Rating
loopbandwidth =d* wn<(1/20 fref)
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…