Electronic – Dual GPS Antenna Connection to Positioning Module

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I am using a Positioning module that has a SMA port to hot plug an SMA antenna. It also has pins available through its footprint to connect a GPS Antenna.

The module name is SIM908. I was not able to spot a place in its data sheet that describes if both antennas can be connected at once.

I want to solder a passive chip antenna about 5-10cm away from the GPS module to be used in case should the external SMA antenna is broken or disconnected. At least with a longer fix time, I would still have some fix, without having no fix at all.

Would having two antennas connected, one through PCB trace and other through direct SMA cable be a problem for the performance of the device?

Best Answer

"Would having two antennas connected, one through PCB trace and other through direct SMA cable be a problem for the performance of the device?"

Absolutely. RF is a fickle creature and having stubs on a PCB is a good way of having neither antenna work.

However, all is not lost. The Hittite/ADI HMC849 is designed to switch between antennas and is not too expensive. If you need it to automatically switch, try detecting any DC current to the external (active) antenna. More than about 2mA and you can safely say an external antenna is plugged in.