raja.cedt wrote on Jun 3rd, 2009, 3:38am:hi buddypoor,
what your are saying is correct but what is the significance of wn? i think the answer is if your loop is really unstable then it oscillate with this frequency.But now zero is introduced but still all PLL papers are using wn is loop bandwidth? why it is?
thanks,
Rajasekhar.
OK, it seems in my first reply at 10:00 I have expressed myself not clear enaugh. I try again:
Wn is the natural frequency of the loop without the additional zero.
After introducing this zero the open loop response changes and we get the 0dB crossing at another frequency (which you call Wu) with another slope. However, this is the new natural frequency of the closed loop - and we should call it again Wn. (The "old" Wn now has no practical meaning and no significance
anymore since the circuit has changed !).
Did you get it now ?
Thanks, Regards
Lutz