Discussion Forum

Your picture seems simple enough. Let's refer to your 3 cylinders as Cyl 1 (the cavity), Cyl 2 (the outer coax), and Cyl 3 (the inner conductor of the coax). I'm going to assume you don't have any dielectrics involved here other than air or a constant dielectric overall, and that the coax ctr is perfectly conducting.

Step 1. Build Cyl 1.
Step 2. Build Cyl 2, making sure that it extends both into and out of Cyl 1 (not just touching it).
Step 3. Form the Union (Right click Geometry, then Boolean --> Union) of Cyl1 and Cyl 2, with the box that says to keep the boundaries not checked. This will form a nice junction.
Step 4. Build Cyl 3.
Step 5. Assuming you wish to model your coax center pin as a perfect conductor, you can now simply subtract it from the structure. I.e., Right click Geometry, then Boolean --> Difference. And be sure you subtract Cyl 3 from the Union you formed earlier.

And that should take care of the geometry. Now you are ready to set up the boundary conditions, mesh, etc., on your model. Hope that helps.

Thanks for the answer.
With this structure, the electric field is confined in the feed and the cavity is not excited ( as you can see in the picture). The parameters of the cavity should be:

- Cavity has air inside and PEC as boundary;
- Cavity has 120 mm radius and 251 width because should be designed by considering fundamental TE mode;
- In materials, cavity and inner conductor have air but outer coax has material (2.1 epsilonr , 1 mur, 0 sigma);

When I made the union of Cyl 1 and Cyl 2 I kept the box that says to keep the input objects checked, otherwise in materials I can't select outer coax to set the material (2.1 epsilonr, 1 mur, 0 sigma).

Ok, seems to me like the model may have worked. Are you simply reporting your results, asking for ideas about why the cavity wasn't appreciably excited, or perhaps something else?

I am sorry, I totally forgot the question. However Yes, I am asking for ideas about why the cavity wasn't appreciably excited.

There are a number of possibilities. I suggest you post your .mph file to the discussion forum. If the solved file is too large, clear the solution and mesh first (on the menu bar, choose Study --> Clear All Solutions. and Mesh --> Clear All Meshes), save it under a new name, and post that file.

Thank you very much for help, I have found the solution and I have putted the lumped port on the highlight face (in the picture) and putted a block between cavity and feed making a union between cavity and block.
Hope that this can be helpful for other people.