Finding inductance and capacitance using S,Y,Z parameters in HFSS

- February 26, 2023 at 8:26 pm
  
  Sneh Patel
  Subscriber
  
  Hello,
  I have this 2 coil spiral inductor design (2 lumped ports in Terminal Network) for which I want to find the self-inductance, mutual inductance, and parasitic capacitance. I used the following formula to calculate the inductance. However, I am getting mixed results for different formulas I have tried. I would appreciate your help to see how I can find the accurate parameters of the 2 coil structure.
  1) L = -1 / (2*pi*F*im(Y11))
  2) L = im(Z11) / (2*pi*F)
  
  Thank you,
- March 2, 2023 at 4:57 pm
  
  Eric Valentino
  Subscriber
  
  Hi Sneh,
  
  This simulation seems the most suited for Maxwell 3D if you can access it, which should allow you to directly plot mutual and self inductance.
  
  For the difference between the two formulas you've tried -- they are extracting the same quantity, but one will be where short circuits are applied to every port besides port 1 (y-parameters) and one where open circuits are applied to every other port (z-parameters). I would expect them to be roughly the same here, and if you remove Port 2 they should be exactly the same. Note that you can also multiply by 1e9 to get a number in the nano-henries.
- April 26, 2023 at 6:21 am
  
  dushyant.marathe
  Ansys Employee
  
  Hi Sneh,
  Thanks for posting your query on Ansys Learning Forum.
  I would like to provide a very generic answer as I am not aware of your design completely.
  To simulate the spiral inductor in HFSS, you should have always 2-ports defined. This means that for single sprial, there should be two ports with respect to return path or ground. HFSS requires closed loop formed with respect to return path and calculates the equivalent closed loop inductance of the net. Therefore it needs to model the return path, a shorter one is always recommended. Using HFSS and expression 1) you can extract loop inductance, by modelling the short at other port and forming a loop to get loop inductance.
  If you have access to Ansys Q3D, it will help you to get loop as well as partial inductances.
  I have attached a you tube link for your reference : Simulation of On-Chip Spiral Inductor Using Ansys Q3D — Lesson 3
  Hope this helps. Thanks.