AnsweredAssumed Answered

Q of an inductor

Question asked by S0K7152 on Aug 16, 2004
Latest reply on Feb 18, 2005 by DJORDJEK

Like • Show 0 Likes0
Comment • 4

Hi
I have a spiral inductor layout in Momentum. I have the S- parameter file generated. How to set up a circuit to calculate the Q of this inductor? Any thoughts?

Thanks

Sam

No one else has this question

Outcomes

4 Replies

nilesh1 Aug 18, 2004 11:06 AM
Mark Correct
Correct Answer
I believe a simple way to calculate Q in the Data Display window is as follows:

Y=stoy(S)

Convert S params to Y params.

Q=-imag(Y12)/real(Y12)

There may be other ways of doing the same thing.

Nilesh 8)
Like • Show 0 Likes0
Actions
S0K7152 Aug 20, 2004 1:58 AM
Mark Correct
Correct Answer
Hi

Is it Z=stoz(S), Q=imag(Z11)/real(Z11).

I have downloaded "Turning RFIC technology into successful design" modelling VCO resonators by momentum, by Martin Wilson from Agilent website.

On page 18 he gave an equation Q=pi*fr*max(dphi/dw)
and a test bench on page 19 using AC simulation. Can you access it and elaborate on the test bench?

Thanks

Sam
Like • Show 0 Likes0
Actions
glcr Aug 21, 2004 4:11 PM
Mark Correct
Correct Answer
As Nilesh offered, there are more ways to skin this kitty .... :P

For a 2-port S-parameter freq swept simulation or measurement of an inductor, convert the S-parameters to Y-parameters via "Y=stoy(S)" equation. Then, commonly published & typical are:

L = -(1/w)*Im(1/Y21)

R = -Re(1/Y21)

Q = -(Im(Y11))/(Re(Y11))

where of course w = 2*pi*freq

No animals were harmed in the typing of this post.
;D
Like • Show 0 Likes0
Actions
DJORDJEK Feb 18, 2005 10:56 PM
Mark Correct
Correct Answer
Hi,

note that differentially excited ind. will have a higher Q than an ind. exicted in a single-ended manner - see Niknejad's book.

The S/Y/Z eq.'s hold fine far from self-res. freq. If parasitic capacitance is large (i.e. due to substrate coupling), as it actually is when operating close to the ind. self-res freq., the ind. behaves as a RLC tank, both mag. and elec. energies are stored, and Wilson's eq. is more applicable.

Dj.
Like • Show 0 Likes0
Actions

Q of an inductor

Outcomes

Related Content

Recommended Content