Hi,
I'm considering the implementation options for nRF91 GPS front end. Having a shared antenna for LTE and GPS would be tempting, but I'm concerned about the filtering/isolation needs.
In the solution proposed in the nRF91 documentation the antenna connection is fed to the GPS input via the AUX pin. Hence apparently there's some kind of internal switch between the ANT and AUX pins of the nRF91.
Now, I wonder what is the attenuation of this internal switch and if it's high enough to prevent the LTE TX leaking in the GPS receiver and causing harmful harmonics? For example, when operating in B13, the 2nd TX harmonic is falling in the middle of the GPS band for which there're very strict emission limits in US.
Possible problem could be mitigated by a band filter in front of the GPS LNA, but this is not recommended in the nRF91 documentation. Is it really not needed?
Regards,
Jyrki
