Electrical – GSM antenna inside metalic enclosure


Is there any efficient way to make an antenna radiate to the outside from inside a close metalic enclosure?
I cannot drill any holes in it, nor place the antenna on the outside, nor change the material type.

I know that the metal acts as a shield and reflector for the radio waves. I was thinking on using a directive antenna and hope that the radio waves find their way out/in somehow, maybe through some open edges.
This seems like some sort of impossible task, you have any alternatives to it?

I'm working over the GSM band.


Best Answer

As you say, the enclosure will block radio waves emitted inside of it.

People often think that a shield should block all radio waves. Technically it does, but in practice it doesn't because the shield itself re-radiates some of the power. You may be able to use this to your advantage.

If one of the dimensions of the box is a multiple of ½ wavelengths, then use the box as your antenna. Connect the two antenna feed lines to opposite points of the box on the inside. Unless you have sophisticated antenna modeling software, you'll need to experiment with a field strength analyzer to see what connection points work best.