Hi all,
I hope this is the right forum to ask for help on this. My product is a wireless cellular/wifi device. It has 2 cellular (broadband 700MHz to about 1900MHz) antennas and 2 wifi (2.4GHz to 5.8GHz) antennas encased in a shell that allows it to be rugged and placed outdoors and on vehicles to provide a semi-hotspot type fucntion in areas with low coverage.
The problem I am running into is when I tried to add a GPS antenna (1.575GHz) inside the enclosure, the GPS will not find a lock until you move the GPS antenna outside of the enclosure. Once you get a lock, you can move the antenna back inside and it wont drop. To me this means that there is definitely a bit of RFI just significant enough to lower the SNR needed when aquiring a lock but not enough to completely block the signal or detune the GPS antenna. At first I thought it was the cellular antennas causing the issue but even after removing them, the problem persists.
The antennas attached via SMA down through a Faraday cage where the board and wireless radios are mounted. My feeling is that the interference is being generated from somewhere on this board and is at a frequency not being blocked by the cage. I've tried to wrap a toroid around the GPS antenna wire however that didnt seem to help. My next step is to try and buy a more broadband toroid (up to 1GHz) whereas the one I am using now is rated for up to 500MHz.
If anyone has any ideas they would be greatly appreciated!