RF Switcher and Current Monitor Sample

Hi there,

I am currently working on a GPS Receiver that is able to support both
internal and external antenna. I would like the system to detect the
external antenna and switch to the external antenna automatically. I
remembered I once read a sampe from a magazine that required a RF switcher
and a Current Shunt Monitor (like INA138) to detect the current, but I
forgoty where it was. Could anybody provide me some information for this
type of circuits design using RF switcher and Current Monitor? Any
recommendation, suggestion, warning, or tips are highly appreciated.

Thanks in advance.

Johnson


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