Over my time working with Ansys HFSS (high-frequency structure simulator), I have learned several modeling and workflow improvements. Whether you are new to HFSS or a seasoned veteran, leveraging these tips will help make your life easier and drive better simulation outcomes. Many of these tips can be used with other tools available in the Electronics Desktop including Maxwell, Icepack, and Q3D.
1) Use keyboard shortcuts
A full list of keyboard shortcuts is available in the HFSS Help guide, but these are some common shortcuts:
B – Select face/object behind current selection (this one is especially useful in crowded models)
F – Select Face O – Select Object E – Select Edge V – Select Vertices
Ctrl + Shift + A – Deselect all objects
Ctrl + D – Fit View (fast method of getting back to full model when you are zoomed in/out)
Alt + Left Mouse – Rotate Shift + Left Mouse – Pan
2) Make duplicate designs within the same project
When you are iterating a design and want to tweak a parameter or make a significant change, it is always a best practice to make a new design. This reduces the risk of losing past simulation data and serves as a point of reference to potentially leverage on future designs. There really is not a benefit to not do this, so simply right click the HFSS design > copy > right click project > paste. Then click on the newly pasted model and rename it accordingly. When you get up to over ten or so designs within a project, I like to start a new project and keep working. I notice that fields post-process faster when you keep the number of designs within a project to a reasonable amount.
3) Rename your projects, designs, and model objects accordingly
When a simulation needs to be completed quickly it is easy to ignore renaming model objects. While this may work for simple models, it is a bad habit that you should try to break quickly. You may understand your design at an intimate level, but others are not going to immediately know which model object is rectangle5 and which is rectangle19. Using the rename and group assignments, your 3D model will look clean and easy to interpret (Fig 1). It a quick task and will save you time as well. Be sure to use underscores when using multiple words in a rename.
Fig 1: Renaming and grouping model objects makes the modeling tree much easier to navigate
4) Use object coordinate systems when drawing model objects
One of the most frustrating issues I encountered when I first started working in HFSS was how model objects would overlap or separate when I would adjust the dimensions on one of them. I recall meticulously adjusting the lengths and start positions until the model object realigned with each other. It was a glorious day when I learned how to correctly leverage object coordinate systems. When an object coordinate system is set on an object, that object can move or change shape and anything that was drawn using that coordinate system will move accordingly as well. Below (Fig 2) you can see what happens when I shorten the antenna arm with and without an object coordinate system assigned.
Fig 2: Antenna Arm Length Adjustment – (1) Before Adjustment; (2) Without Object Coordinate System; (3) With Object Coordinate System
5) Use design variables
One of the single most significant workflow improvements you can do is to begin using design variables. Design variables allow you to quickly change model parameters within your simulation. To assign a design variable write the variable name in the value box (Fig 3). An “Add Variable” window will pop up for you to assign the value. Be sure to assign the correct unit type and unit; do not leave these blank if possible. Now that Ansys Optimetrics comes standard in HFSS Premium, it makes sense to leverage this tool to optimize your designs. To perform optimizations and tuning, the model needs to have these design variables assigned to know what can change during the optimization study. If you already incorporate variable assignment in your current workflow, that is great! Consider adding even more. You may be surprised that a previously fixed model object could improve the design if subjected to an Optimetrics sweep.
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