Solution setup functions in HFSS 9.0

hfss max function

I am working on microstrip antenna design in HFSS 9.0. I learned more about it by the help of traning (A friend gives me) but I don't understand some functions' physical meaning in this program. In solution setup there are options: maximum number of passes and Maximum delta S per pass.
If anyone explains their meaning and how to use them, I am grateful to him.
Thanks

max delta hfss

the simulation will terminate when either of these 2 criteria is met.

if you set the maximum number of passes to 6 and the model does not converge within 6 passes the simulation will stop regardless.

the maximum delta s defines the convergence criteria, if you use 0.02 it means that when the difference between two passes is less than 2% the model has converged and thus terminates.

delta s per pass and hfss

Maximum number of passes is the value that you specify in order for the algorithm to keep going in case the maximum S delta % has not been achieved. The S delta % refers to how much error do you tolerate when calculating S-parameters, and the number of passes is how many times do you want to repeat the algorithm is the delta % has not been satisfied.

thanks for reply, can you expand this explanation a bit further.

Hi,

HFSS using convergence in order to get an accurate solution. After creating an initial mesh it starts doing adaptive passes until the desired error residual is achieved. In each stage it refines the mesh and resolves the problem. The resulting S-Matrix is compared to the previous one. The maximum delta is computed in percentage. If the max error found is 3% and you specified Maximum delta S per pass.to be 0.02=2% then it will continue with another meshing and solving. If the max error found is reduced to 1.5% the solution is "converged" and the simulation will stop.

In order to control this process you have a few options:
1) Maximum number of passes - Allows you to stop after several passes. Even if you want faster solution times I recommend not to use this option and set it to 20.
2) Maximum delta S per pass - Allows you to define the desired accuracy for the solution. For example, in many Signal Integrity applications 4% is more than enough.
3) Refinment per pass - for simple problems increase from 20% to 30%. This controls the amount of mesh refignment between passes.
4) Minimum converged passes - I recommend to set it to 1. This allows you to force HFSS to continue more adaptive passes even after it converged.
5) Port accuracy. The default is 2%. This controls the accuracy of the 2D solution on the port. If you are solving ports only (for example to calculate effective lambda for a transmition line) - I recommend to increase accuracy from 2% to 0.3% or even 0.1%.


Itai