phase shift of an inductor

[Supaswing]

Hi everybody,
A question quite simple :
When I model an inductor with MWS, I get a phase angle of about 180 or -180, somethimes 0 deg.
I always thought that an inductor induces a lag of 90deg. ( little less for real inductor with R and C) why isnt it the case in the simulation ?
David

small edit :
By shifting the phase of S11 by 90degree (i.e to get a pi/2 phase at low frequency) I get the input impedance very close from measurment, is there a meaning??

 

[neoflash]

How you measure S11?

What is the phase shift you are talking about?

 

[Supaswing]

I calculated the S-parameters in MicrowaveStudio, not measured them.
In FDTD, you take the FFT of the time domain responses and divide them, so S11= FFT(reflected output o11) ./ FFT(input i1).
I put two plot, one from taken from Murata for a similar inductor
the other from my calc.
If you can have a look...
Regards,
David.

 

[neoflash]

Your network looks like:
src(R)--(Port1)---L---(Port 2)--probe(R)

S11=(jwl+R-R) / (jwl+R+R)=jwl/(jwl+2R)
when w (frequncy) is low, the phase shift is about 90 dgree. It is approaching zero, when jwl gets large.

When self-resonant happens, it is very close to zero. I hope it helps.

 

[Supaswing]

Thank you for the equation, I totally agree with you and that why I do not understand the behaviour of the simulations...
For the S parameter to be wrong there must be an error in the time domain propagation, but I cannot see which one, I tested mesh, ports, boundaries, material, etc..
I suspect the excitation, the frequency range, or solver parameter (courant number, etc..)
BTW, is there a clear limit wether FDTD doesn't work? for example to low propagation constant.