NEO-M8P - Hardware Integration Manual
UBX-15028081 - R05
Early Production Information
Product handling
Page 21 of 27
EOS protection measures
For designs with GNSS positioning modules and wireless transceivers (e.g. GSM/GPRS) in close proximity,
ensure sufficient isolation between the wireless and GNSS antennas. If the wireless power output causes
the specified maximum power input at the GNSS RF_IN to be exceeded, employ EOS protection measures
to prevent overstress damage.
For robustness, EOS protection measures as shown in Figure 12 are recommended for designs combining wireless
communication transceivers (e.g. GSM, GPRS) and GNSS in the same design or in close proximity.
Small passive antennas
(<2 dBic and performance
critical)
Passive antennas
(>2 dBic or
performance sufficient)
Active antennas
(without internal filter which need the
module antenna supervisor circuits)
D
RF
_
IN
LNA
GPS
Bandpass
Filtler
3.3.1.1.1.1.1.1
E
3.3.1.1.1.1.1.2
L
GPS
Bandpass
Filtler
3.3.1.1.1.1.1.2.1
F
3.3.1.1.1.1.1.2.2
LNA with appropriate ESD
rating and maximum input
power
GNSS Band pass Filter: SAW or Ceramic
with low insertion loss and appropriate ESD
rating
Figure 12: EOS and ESD Precautions
Electromagnetic interference (EMI)
Electromagnetic interference (EMI) is the addition or coupling of energy causing a spontaneous reset of the GNSS
receiver or resulting in unstable performance. In addition to EMI degradation due to self-jamming (see section 1.5)
any electronic device near the GNSS receiver can emit noise that can lead to EMI disturbances or damage.
The following elements are critical regarding EMI:
•
Unshielded connectors (e.g. pin rows etc.)
•
Weakly shielded lines on PCB (e.g. on top or bottom layer and especially at the border of a PCB)
•
Weak GND concept (e.g. small and/or long ground line connections)
EMI protection measures are recommended when RF emitting devices are near the GNSS receiver. To minimize
the effect of EMI a robust grounding concept is essential. To achieve electromagnetic robustness follow the
standard EMI suppression techniques.
http://www.murata.com/products/emc/knowhow/index.html
http://www.murata.com/products/emc/knowhow/pdf/4to5e.pdf
Improved EMI protection can be achieved by inserting a resistor, or better yet, a ferrite bead or an inductor (see
Table 4) into any unshielded PCB lines connected to the GNSS receiver. Place the resistor as close as possible to
the GNSS receiver pin.
Alternatively, feed-thru capacitors with good GND connection can be used to protect e.g. the
VCC
supply pin
against EMI. A selection of feed-thru capacitors are listed in Table 4.
