[SI-LIST] Re: PCB Trace impedance algorithms

 A simple answer to your question (from memory):
Field simulators usually give three impedances, Zpi, Zvi, and Zpv.

Zpi: Calculated from the power through the port and integration of
magnetic current in a loop around the port. Useful for microstrip,
stripline, and coaxial.

Zpv: Calculated from the power through the port and integration of
the E-field voltage along a user-specified path or "calibration line",
typically from the conductor to ground. Useful for coplanar waveguide.

Zvi: The geometric mean of Zpi and Zpv. Never very useful for me.

Non-FEM solvers might use a different approach, but the results
generally agree, so they probably use the same approach.

--
Daniel Gunyan

  ----- Original Message -----
  From: "Sam Sam"
  To: si-list@xxxxxxxxxxxxx
  Subject: [SI-LIST] Re: PCB Trace impedance algorithms
  Date: Tue, 23 Jan 2007 21:03:35 -0500 (EST)


  Dear all,

  Thanks for all your answers. I will definitely go over the references
  you mentioned to help
  me more.

  John,

  I understand full wave field solvers provide accurate answers
  compared to formulas at the
  cost of the computational time. How is the impedance calculated from
  the field solutions? If i
  calculate my scattering parameters, is it possible to find the
  impedance of the trace from that?
  As you mentioned allegro uses BEM field solver, they should be able
  to calculate the impedance
  matrices to do that?

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