Stability in CST MWS

Hi everybody,

i am simulating some antennas for milimeterwave application. Sometimes the simulation was aborted due to unstable state and the logfile suggests a smaller stability factor for the transient solver or a smaller PBA fill limit.

The simulation runs when i changed the stabily factor for timestep in the special settings to 0.7 (default was 1.0 ). Will this lead to an unaccurate S-Parameter result ? What about a smaller PBA fill limit ? I haven't tried it yet.

Or is there any other reason which could be the cause for the unstable state during the simulation ?

Thanks for your help.

Regards,
abti

Hi,

the time step should to affect the results (only the calculation time) If you reduce the PBA fill limit to let say 70% (default 99%) the PBA cell is only used if the cell if filled with less the 70% by metal. If the cell is filled by more then 70% by metal, the entire cell is considered to be metal.

Sometimes the port setup can influence the stability. Try to switch off "absorb unconsidered mode fields" in the solver special settings...

F.

i find it difficult to simulate high Q structure in CST, it tooks forever to simulate, anyone has any idea dealing with high Q structure in CST?

Try to use the eigenmode solver in CST. But it works good only in narrow band.

Best regards,
Kit

the tricked of simulating high Q structure using CST MWS is the AR-filter, there is an slides from the CST for explanation the AR-filter.
Best Regards,

try to minimize the frequency range. I had to simulate many broadband antennas. E.g. you need the range 5-6GHz and simulate from 0-8GHz to get an overview. The results can look totally different and the calculation takes forever. The time for excitation will need much longer for the minimized range but you will get much better results.