currently working on a design to extend GPS signal under water. The GPS signal from the surface is amplified and sent over a coax to the receiver under water. At the end of the coax the antenna is mounted( SRFg017) the antenna is in a waterproof casing( POM/Delrin) it is a small enclusure. This enclosure is piggy backed to the recievers patch antenna. The purpose is to transfer the signal over to the receivers patch antenna. What I see s that the impedance of the antenna is verry good in free air, but verry bad in the enclosure. This due to the very near proximity of the PM/Delrin and water that surrounds this enclosure. In the water the resonant frequency is not 1575MHz, but about 1900MHz.
What would be a good design approach to have an antenna in resonance in this water envionment? Hope you can help.
Regards, Rob van Vreden