Discussion Forum

If you want to model the radiation properties of the antenna, you will always need to have at least some space around the antenna, to allow the antenna to radiate. The simple conical antenna example that Comsol included with the application library for the RF module shows you one way (not the only way) to build such models. To make your own monopole antenna, you could simply change the shape of the mono-cone in their example.

This example is 2D. The problem is once the sphere is defined it is not possible to alter the inner structure and if I delete the sphere calculation is wrong. There should be a very simple workaround but can't seem to follow up how to.

I'm not sure where you are running into trouble. I suspect you are very new to using this software. Anyway, basically what you need to do is first draw your antenna geometry (in 2D or 3D, whichever is physically appropriate), and that must include a region for radiation to go into, and should also include an appropriate port to drive the antenna. For a PEC antenna, you can indeed subtract it from the model, and leave only its boundary conditions (including a port) while, of course, also keeping the radiating space. Again, you must never, never throw away the radiating space. OK, so mesh it, solve it, look at results, etc. Then, if you want to change the antenna's shape, simply go back and change the geometry in the exact same place you specified it originally. Then mesh it again and run it again, etc.. With practice and experience, you can learn to do more complicated things, like how to put a geometric parameter in a loop and obtain solutions for multiple shapes in sequence. Study the examples for other kinds of problems, not just antennas, if you want to know how to effectively prepare problems to run in Comsol Multiphysics.

I'm not sure where you are running into trouble. I suspect you are very new to using this software. Anyway, basically what you need to do is first draw your antenna geometry (in 2D or 3D, whichever is physically appropriate), and that must include a region for radiation to go into, and should also include an appropriate port to drive the antenna. For a PEC antenna, you can indeed subtract it from the model, and leave only its boundary conditions (including a port) while, of course, also keeping the radiating space. Again, you must never, never throw away the radiating space. OK, so mesh it, solve it, look at results, etc. Then, if you want to change the antenna's shape, simply go back and change the geometry in the exact same place you specified it originally. Then mesh it again and run it again, etc.. With practice and experience, you can learn to do more complicated things, like how to put a geometric parameter in a loop and obtain solutions for multiple shapes in sequence. Study the examples for other kinds of problems, not just antennas, if you want to know how to effectively prepare problems to run in Comsol Multiphysics.

Thank you for the answer.