User's Manual

LE920 Hardware User Guide
1vv0301026 Rev.8 2015-01-03
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved. Page 49 of 88
NOTE:
It is recommended to add a DC block to the customer’s GPS application in order to prevent
damage to the LE920 due to unwanted DC voltage
WARNING:
The LE920 software is implemented differently depending on the configurations of an external
device. Please refer to the AT command User Guide in detail.
6.5.1. Combined GPS/GNSS Antenna
The use of combined RF/GPS/GNSS antenna is NOT recommended. This solution could
generate extremely poor GPS/GNSS reception. In addition, the combination of antennas
requires an additional diplexer, which adds significant power losses in the RF path.
6.5.2. Linear and Patch GPS/GNSS Antenna
Using this 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 behaviour & create poor position accuracy.
6.5.3. Front End Design Considerations
When using the Telit LE920, since there’s no antenna connector on the module, the antenna
must be connected to the LE920 through the PCB to the antenna pad.
In the case that the antenna is not directly connected at the antenna pad of the LE920, 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 LE920 ground pads