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GPS antenna interference in middle of 4 other antennas

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!

Andrew Beckett over 11 years ago

This forum is more for RF IC Design, and even then a lot of it is about simulation and tooling issues rather than actual design.
You may find going to the Designer's Guide Forums a more productive place to ask such questions?
Regards,
Andrew.
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