LEA-6 / NEO-6 / MAX-6 - Hardware Integration Manual
UBX-14054794
Production Information
Product handling
Page 61 of 85
3.3.8
Applications with wireless modules LEON / LISA
GSM uses power levels up to 2 W (+33 dBm). Consult the Data Sheet for the absolute maximum power input at
the GPS receiver.
3.3.8.1
Isolation between GPS and GSM antenna
In a handheld type design an isolation of approximately 20dB can be reached with careful placement of the
antennas. If such isolation can’t be achieved, e.g. in the case of an integrated GSM/GPS antenna, an additional
input filter is needed on the GPS side to block the high energy emitted by the GSM transmitter. Examples of
these kinds of filters would be the SAW Filters from Epcos (B9444 or B7839) or Murata.
3.3.8.2
Increasing jamming immunity
Jamming signals come from in-band and out-band frequency sources.
3.3.8.3
In-band jamming
With in-band jamming the signal frequency is very close to the GPS/QZSS band of 1.575 GHz and GLONASS
band of 1.602 GHz (see
Figure 59). Such jamming signals are typically caused by harmonics from displays, micro-
controller, bus systems, etc.
1525
1550
1625
GPS input filter
characteristics
1575
1600
0
-110
Jammin
g signal
1525
1550
1625
Frequency [MHz]
Power [dBm]
GPS input filter
characteristics
1575
1600
0
Jamming
signal
GPS
signals
GPS Carrier
1575.4 MHz
Figure 59: In-band jamming signals
Figure 60: In-band jamming sources
