ZOE-M8 series - Hardware integration manual
UBX-16030136 - R09
Design-in
Page 23 of 34
Production information
Intended use
☞
To mitigate any performance degradation of a radio equipment under EMC disturbance, system
integration shall adopt the appropriate EMC design practice and not contain cables over three
meters on signal and supply ports.
2.14.6
Applications with cellular modules
GSM terminals transmit power levels up to 2 W (+33 dBm) peak, 3G and LTE up to 250 mW
continuous. Consult the ZOE-M8 Data sheet [1] for the absolute maximum power input at the GNSS
receiver. Make sure that the absolute maximum input power level of the GNSS receiver is not
exceeded.
☞
See the GPS Implementation and Aiding Features in u-blox wireless modules [5].
2.14.6.1
Isolation between GNSS and GSM antenna
In a handheld type design, an isolation of approximately 20 dB can be reached with careful placement
of the antennas. If such isolation cannot be achieved, for example, in the case of an integrated
GSM/GNSS antenna, an additional input filter is needed on the GNSS side to block the high energy
emitted by the GSM transmitter. Examples of these kinds of filters are the SAW Filters from Epcos
(B9444 or B7839) or Murata.
2.14.6.2
Increasing interference immunity
Interference signals come from in-band and out-band frequency sources.
2.14.6.3
In-band interference
With in-band interference, the signal frequency is very close to the GPS frequency of 1575 MHz (see
Figure 16). Such interference signals are typically caused by harmonics from displays, micro-
controllers, bus systems, and so on.
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
Interference
signal
GPS
signals
GPS Carrier
1575.4 MHz
Figure 16: In-band interference signals
Figure 17: In-band interference sources
