User's Manual

GE/GC864-QUAD V2 and GE864-GPS Hardware User Guide
1vv0300915 Rev.2 – 2011-06-15
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights
Reserved. Page 52 of 97
NOTE: The absolute maximum rating for GPS RF input power is 10
dBm
7.3.2. Combined GPS Antenna
The use of combined GPS antennas is NOT recommended; this
solution could generate an extremely poor GPS reception and
also the combination antenna requires additional diplexer and
adds a loss in the RF route.
7.3.3. Linear and Patch GPS Antenna
Using this type of antenna introduces at least 3 dB 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.
7.3.4. GPS Antenna - PCB Line Guidelines
• Ensure that the antenna line impedance is 50Ω.
• Keep the antenna line on the PCB as short as possible
to reduce the loss.
• Antenna line must have uniform characteristics,
constant cross section, avoid meanders and abrupt
curves.
• Keep one layer of the PCB used only for the Ground
plane, if possible.
• Surround (on the sides, over and under) the antenna
line on PCB with Ground, avoid having other signal
tracks facing directly the antenna line of track.
• The ground around the antenna line on PCB has to be
strictly connected to the Ground Plane by placing vias
once per 2mm at least.
• Place EM noisy devices as far as possible from GE864-
GPS antenna line.
• Keep the antenna line far away from the GE864-GPS
power supply lines.
• Keep the antenna line far away from the GE864-GPS GSM
RF lines.
• If you have EM noisy devices around the PCB hosting
the GE864-GPS, such as fast switching ICs, take care
of the shielding of the antenna line by burying it
inside the layers of PCB and surround it with Ground
planes, or shield it with a metal frame cover.