How to set up the source when using a coaxial feed for a microstrip form antenna?

[HuangJL]

Hello,I sincerely ask for help.
I'm wondering how to set up the source when using a coaxial feed for a microstrip form antenna?
Should I use an edge source or a waveguide source?
Does the inner and outer coaxial diameters need to be extended?
The simulation results do not seem to converge and the reflection coefficient is greater than zero dB.
Is the source setup method below correct?

[brown]

Have you tried taking a look at the 'Coaxial to Rectangular Waveguide Transition' tutorial?

Could you share what your voxels look like? It would be good to see if all of the components got included, like the outer layer of the coax.

[HuangJL]

Yes，I have seen that tutorial. So I set the source like the coaxial in tutorial.
The antenna is to be implanted into body, so the size is small. (Coaxial outer radius 0.35mm)

[brown]

Here are a few more things you can check for this case:

• Making the coax longer
• Moving the waveguide source a bit inside the coax
• Making sure that the coax is terminated with PML by changing the Padding Settings to Manual, and setting the grid padding to be zero on the side where the coax ends
• Changing Boundary Conditions Strength to High on all sides

[HuangJL]

@brown
Thank you, I will check these things. Additionally, there are some warning messages which may help:

Is the mesh division not precise enough？