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Antenna tissue interface-temperature and boundary conditions (Electromagnetics + Bioheat)
Posted 2017年10月9日 GMT-4 12:44 Electromagnetic Heating, RF & Microwave Engineering, Interfacing 0 Replies
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Hi,
I am trying to simulate a simple antenna radiating into a block of a tissue using EMW and Bioheat physics and have followed the tutorial from https://www.comsol.com/model/microwave-heating-of-a-cancer-tumor-30
Initially, I inserted the antenna end into the tissue for about 5 mm and subtracted it from the tissue. The antenna end is cylindrical and is made up of ceramic with metal coatings on the side faces. I am facing these major issues and would be really helpful if someone could highlight and/or point out any missing items relating to any of the issues:
1) Setting up “Perfect Electric” (PE) boundaries to the metal coatings on the side faces of the ceramic end situated in the tissue provides expected S11 (~-12dB) however the temperatures soar to 70-80 degrees in 2 seconds or so (the expected value of T is around 45 degrees). On the other hand, not setting up PE boundaries yields expected temperatures but that is perhaps due to the fact that S11 is poor (~-5dB)
2) I have set up “Temperature” boundary conditions on the tissue boundaries including the common boundary shared by the ceramic tip and the tissue, however this results in a bit unrealistic temperature distribution pattern. Excluding the ceramic-tissue interface boundary in the Temperature boundary condition results in an expected temperature distribution pattern but the temperature values are unrealistic (~100 deg in 2 sec). I have meshed the antenna-tissue interface boundaries a bit finer as well.
3) Finally, and perhaps the strangest of all, if I keep every other variable same, and move the antenna position i.e. go deeper than 5 mm or bring it back to apply it just on the edge of tissue, the temperature values change significantly. In general, antenna tip on the edge of the tissue yields much higher values than when it is located deeper in the tissue. Considering the fact that the ceramic end is subtracted from the tissue, it should not make any difference? I have checked the material properties, geometries, meshes, radiation boundaries, port plenty of times but no success yet. I would really appreciate your comments.
Many thanks,
Shailesh
Hello Shailesh Joshi
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