
xE922-3GR Hardware User Guide
1VV0301272
Rev.0.8 2017-01-05
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved.
Page 94 of 112
In case of an internal antenna configuration, it is important to keep the 50 ohm transmission
line (TL) short to limit possible signal degradation between antenna and internal LNA amplifier.
In case of an active external antenna, a bias circuit to feed the antenna integrated LNA is
required. An inductor filter is used as RF block. Also a DC-block capacitor is required in order
to keep unwanted DC voltage away from the internal RF FE devices.
Care should be taken to minimize stubs on the 50ohm PCB structure because of placement of
these additional bias components.
16.3.1.
Combined GNSS Antenna
The use of combined RF/GNSS antenna is NOT recommended. This solution could generate
extremely poor GNSS reception. In addition, the combination of antennas requires an additional
diplexer, which adds significant power losses in the RF path.
16.3.2.
Linear and Patch GNSS Antenna
Using linear type of antenna introduces at least 3dB of loss compared to a circularly polarized
(CP) antenna. Having a spherical gain response instead of a hemispherical gain response could
aggravate the multipath behavior & create poor position accuracy.
16.3.3.
Front End Design Considerations
When using the Telit xE922-3GR, since there is no antenna connector on the module, the
antenna must be connected to the xE922-3GR through the PCB to the antenna pad.
In the case that the antenna is not directly connected at the antenna pad of the xE922-3GR, then
a PCB line is required.
This line of transmission shall fulfill the following requirements:
Antenna Line on PCB Requirements
Characteristic Impedance
50Ohm
Max Attenuation
0.3dB
Coupling with other signals shall be avoided
Cold End (Ground Plane) of antenna shall be equipotential to the xE922-3GR ground pads
Furthermore if the device is developed for the US and/or Canada market, it must comply with
the FCC and/or IC requirements.
This device is to be used only for mobile and fixed application.