Depending on the device concept, tuning the LTE antenna to cover Global Positioning System (GPS) may be advantageous. The GPS antenna requirements specified in GPS antenna and front-end requirements apply also to the combined GPS and LTE antenna at GPS frequency. To fulfil the LTE TX band rejection requirement, a switch is needed to isolate the GPS input from the LTE transmitter.
nRF9160 includes a 50 Ω RX auxiliary (AUX) path that can be used to loop back the signal fed into the ANT pin. The AUX can be used when two radios share an antenna. In case of a combined GPS and LTE antenna, an internal RF switch in nRF9160 provides the needed isolation between the GPS and LTE paths. When the GPS receiver is on, the antenna is switched to the AUX and through an external Low-Noise Amplifier (LNA) to the GPS input. To minimize mismatch losses, using external matching components between AUX and LNA is recommended.