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elena
Antenna-Theory.com Newbie

Joined: 10 May 2010
Posts: 7

 Posted: Tue Jun 08, 2010 7:25 pm    Post subject: Antenna bending in a human body. Hello, I have to bend a patch antenna in the human body. The human body will be implemnented by a body tissue simulating liquid with er=52.7 and conduct=1.95. So I made a cylinder in CST using the material properties above. WHen I start transient frequency with the bending antenna it gives me about 97 million cells without adapting meshing, probably i am doing sth wrong... My actually steps are: substrate cylinder-groundplane-substrate for antenna-patch Please help me if these are the correct steps or do I need to do anything else Or should I use a cylinder as a container and filled with this liquid? If yes how can I make in CST a cylinder let say made of polyethylene and filled it with the body tissue liquid. Thaaanks
Schubert
Antenna Wizard

Joined: 08 Apr 2009
Posts: 161

 Posted: Wed Jun 09, 2010 4:47 am    Post subject: I'm not sure what solution method CST uses, but it sounds like it is FEM. If you have to mesh a volume, you can really only do 1-2 wavelengths on each side of a cube. Not much volume. This is one of the many limits of computation electromagnetics (not to mention unknown accuracy, modeling error, numerical error, etc). You'll have to work within these limits. CST might have some helpful ideas (often if the volume has symmetry, it can do twice the volume it could otherwise) - read some of the instruction manual for this. If at all possible, if you have access to a network analyzer, just build a simple antenna and surround it by some high dielectric material to get a good idea of what is happening. In general, you should see the resonant frequency shift way lower (if the antenna resonates at 1 GHz in free space, it will resonate at 100 MHz or so in a high dielectric medium). In addition, the efficiency will drop due to the surrounding conductivity. Hope this help. Sorry, I'm not such a proponent of numerical software.
elena
Antenna-Theory.com Newbie

Joined: 10 May 2010
Posts: 7

 Posted: Wed Jun 09, 2010 11:03 am    Post subject: Thanks a lot for your info. Actually I am using the transient solver and as I mentioned above the number of cells is huge, I tried your idea about taking the volume symetry but again the number of cell is at about 42 million without adaptive meshing. As it is a big structure related to my operation freqency we can not use the transient or frequency solver. For big structure we can use the asymptotic solver , but unfortunately it works only for PEC large structure. Probably I have to use the CST voxel in order to see how the resonant frequency shift and generally the interacction of the body with the antenna.
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