calculate tank lc q

How to simulate Q of LC Tank in ADS
I want to complete a differtential LC
VCO . The varactor is voltage controlled and
I want to see Q of LC Tank in different varactor
capacitance .

check the tutorials on

www.rfic.co.uk

i hope it is usefull to u

The simplest way to calculate Q is F0/BW(3dB).
As I understand there is an inductor and a varactor in parallel or series. This tank is connected somehow to the VCO circuit. If you use it as a reflected circuit- For example the LC parallel tank is connected to the BJT base , then look at S11 . If you use it for a feedback such as parallel LC for cross coupled VCO, simulate S21.

YES , the vco I want to simulate is cross coupled
differential LC VCO . But S21 means gain , doesn't
it ? How can I relate it with Q of lc tank ?

Another problem is that
I want to choose the optimized rf inductor provided by umc .18 process ? I have read Hajimiri's paper about how to choose the inductor to optimize lc vco phase noise . But it's to complicated and hard to implement for me . So I decided to use asitic software to choose optimized geometry inductor . But I meet a big problem is that umc
foundry doesn't provided the ohmic resivity for
every layer such that I can't make technology file
for asitic to simulate . So can any body provided
me the asitic 0.18um umc technology file .
Thank you sincerely .

Try this
http://www.ece.cmu.edu/~mems/pubs/pd...awala-2000.pdf

Thank for you provide this link . But I use
0.18um UMC "Al" process not "Cu" process .

iemotions,
LC parallel tank is located in the C of the BJT (or D of CMOC) and used as a BPF. The loaded Q factor is a function of the load (D(or C) and G(or B) .
For a start point simulate the LC parallel tank as a BPF, means S21, and calculate the Q factor, based on L and C models of course.