HE920 Hardware User Guide
1vv0301014 Rev.9 – 2014-01-23
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved.
Page 45 of 84
NOTE:
If the RX Diversity is not used/connected, disable the Diversity functionality using the
AT#CRXD command and leave the pad AU9 unconnected. Please refer to the AT command
User Guide in detail.
6.5.
GPS/GNSS Antenna Requirements
The use of an active GPS/GNSS antenna is required to achieve better performance.
The module is provided with a Digital Output signal to enable the external LNA (pad V2).
Parameter
Min
Max
Output high level
1.35V
1.8V
Output low level
0V
0.45V
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 and also the combined antenna requires
additional diplexer and adds a loss in the RF route.
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 if 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.
LNA and Front End Design Considerations
Depending on the characteristics and requirements unique to the customer’s designs, the use
of an external LNA or an external active antenna may be required to achieve best
performance.
The optional external LNA should be dimensioned to avoid an excessive LNA gain that can
introduce jamming, spurious, degrade IIP3, and saturate the receiver.
The configurations of an external device must fulfill the following requirements:
An external passive antenna (GPS only)
An external active antenna (GPS or GNSS)
An external passive antenna, GNSS pre-Filter and GNSS LNA (GPS or GNSS)
