Please explain me how no. of pass effect the result .I am simulating an antenna micromachined antenna at 14.5 GHz but it takes a lot of time but when i decrease the no. of pass it work quite faster , do this will effect the result of antenna?
Your Question is related with convergence (or 'correctness') of the solution, which in HFSS for Driven simulations is evaluated on the basis of the scattering parameters observed at each port.
HFSS uses adaptive meshing, which is to say that it sets up an initial mesh, solves the fields, and then re-meshes based on where the fields have a high concentration and/or gradient. Each re-meshing step is called an "adaptive pass". Importantly, at each step, the scattering parameters are evaluated at each port, and compared to the previous step. The difference between the two is called "delta S".
So, in order to make sure a simulation is correct, HFSS does adaptive passes until the delta S falls below a set threshold. HFSS also gives you a large degree of control over this process: you can set delta S to be whatever you want, and you can also tell it to do a maximum number of passes, such that the simulation will stop whether or not the scattering parameters have converged.
Hope this helps!
Hello,
To refine and to increase accuracy, no of passes are used. There are many options, in which simulator runs very close, close and far range of frequency and at resonance frequency too. This is possible only when adaptive passes are being used.
Thanks,
@Vikas
The total number of mesh elements increases with every pass you solve. This is in reference to Adaptive Mesh Refinement method used in the solver. Hence it solved your problem faster when you decided to use less number of passes. The more passes you use, the closer your solution is towards accuracy, but at an added cost of computational time required to solve the problem. So it is a trade off between simulation time and accuracy.
As mentioned above in one of the posts, judicious selection of accuracy threshold can help you converge to accuracy in less number of passes and with reasonable accuracy.
HFSS uses finite element method . It creates a mesh and then the process goes on to calculate different papmetes like scattering parameter ,vswr etc. The difference between each adeptive pass is delta S. To get maximum accuracy we can change the delta S also. But the important question is how many passes we can take? For this we have to do two things. At first take the default no of passes which is 6 and simulate. After that if the warning occurs and a message is shown "poor convergence" then we can increase the no. Passes. If no warning then there will be a green cylinder shaped symbol will come and it will indicate simulation is complete successfully with out any abnormalities. While taking the results also we have to take into account sweep instade of last adeptive. Another thing I want add, Ansys Electromagnetic Solution is a package of software which include HFSS, Maxwell simulator etc. Some of my friends told me its performance is better compared to conventional HFSS. Thank You. I hope it will help.
Is there a minimum number of passes option, since if at say 4th and 5th pass if convergence takes place it will stop evaluating and produce the results but after 5th step if there is a change in S11 plot it will not be able to evaluate. So if minimum no.of pass is set then it can simulation for considerable no.of times. Is my understanding right?
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