How does HFSS work

Forum: HF, radio and fields Antenna and circuit simulation with HFSS

Hello, I am simulating antennas under HFSS. Unfortunately, I don't have that much idea. Does anyone know a good tutorial or experience in dealing with HFSS or is there help on the internet ( & I haven't found a book on HFSS in our library. Drawing the structures and operating the program is no longer the problem, but rather defining the boundary conditions, convergence criteria, etc. for specific examples. Unfortunately, I don't know whether I can trust the simulations and whether my boundary conditions for the problem are correct and have been taken into account accordingly in the program. The manual for the program is quite extensive and therefore you can only read individual things. How would you proceed in my position?

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The program comes with some manuals ('Getting Started') and also with extensive online help. However, with programs such as Ansoft HFSS, Agilent ADS, CST Microwave Studio or APLAC, sooner or later you will not be able to avoid contacting the user support. After all, these are high-end programs for over 20k euros, and they are correspondingly extensive. Your company or university has certainly signed such a support contract, meanwhile you could not buy the programs without one. At CST it happens to me that even the support people don't know everything and you have to wait a long time for a suitable answer ...

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Under Google you can find a lot with + ansoft + hfss + tutorial, including I would also stick to the examples provided. > Unfortunately, I don't know whether I can trust the simulations and> my boundary conditions for the problem are correct and have been taken into account in the> program. You will never really know ..., in case of doubt I always send my complete simulation model to support to check it out. Maybe annoying the employees, but we pay € 7,000 a year just for support. You only know whether the selected boundary conditions have been chosen correctly by reading through the manual to see what causes which RBs and by checking the plausibility of the results obtained. I don't know whether there is something with HFSS underneath, but it describes the use of Ansoft Designer and other high-frequency programs.

OK thank you. With the links from Ansoft there was a lot that I could use. Due to my lack of experience in the field of HF simulations, I would like to know how reliable HFSS simulations are, i.e. at what percentage can the results be trusted? Funny question, I know, but maybe someone can comment on that.

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It is of course best to model and simulate a component that has already been measured and to compare the measurement results with the simulation results. I.a. programs like HFSS or Microwave Studio are VERY accurate. The question is more whether you can actually measure your device in the way the model is built. In real life you have test leads that have to be connected somehow and other things (even if they are just solder blobs) that influence the result, but were not taken into account in the simulation.

So that means that you should simulate the complete structure if possible. Another question arises for me. Can you develop scalable models? I would like to simulate and measure the structure for low frequencies and then transfer the findings to higher frequencies by changing the dimensions of the structure. Is that possible. Which antenna sizes are given the most attention in practice? Impedance, S-parameter, gain and directional characteristic?

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The time when I worked with HFSS was a little longer ago ... At that time, for example, you had to model a stub of coaxial cable with a planar antenna, because otherwise there was no feed possibility for the wave port. Scalable? So with Microwave Studio there is a function with which you can copy, move, rotate, mirror or scale individual elements. Alternatively, you can use variables when creating your model. If the same is changed, the model is automatically updated. With an antenna you only have one S-parameter, S11, which is a measure of the input impedance and the adaptation. I.a. I would say that all of the properties you mentioned must be taken into account when designing an antenna. In the frequency band to be covered, you want to achieve a good adaptation and the desired directional characteristic. What kind of antennas and what do you want to simulate for? In order to help the domestic WiFi on the jumps, the program would have shot at sparrows with cannons. And if it's for university or work, someone has to be able to tell you where you're going, what is the goal, what are the requirements?

Thank you for the answers. It's already for university and at the moment I'm simulating antennas that should be as broadband as possible and have to have a low impedance, at f <10 GHz. So far I've focused almost exclusively on S11. It's good to know that's right. Is there a "quick and dirty" method that can be used to examine antennas?

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