NEO-8Q / NEO-M8 - Hardware integration manual
UBX-15029985 - Production information
Product handling
Page 24 of 25
C1-Public
EOS protection measures
☞
For designs with GNSS positioning modules and wireless (for example, cellular) transceivers in
close proximity, ensure sufficient isolation between the wireless and GNSS antennas. If 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 13 are recommended for designs
combining wireless communication transceivers (for example, cellular) 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
G
NS
S
Rec
ei
ver
LNA
GPS
Bandpass
Filtler
E
RF
_IN
G
NS
S
Rec
ei
ver
L
GPS
Bandpass
Filtler
F
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 13: 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 (for example, pin rows)
•
Weakly shielded lines on PCB (for example, on top or bottom layer and especially at the border of
a PCB)
•
Weak GND concept (for example, 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 6) into any unshielded PCB lines connected to the GNSS receiver. Place the
resistor as close to the GNSS receiver pin as possible.
Alternatively, feed-through capacitors with good GND connection can be used to protect, for example,
the
VCC
supply pin against EMI. A selection of feed-through capacitors is listed in Table 6.
Intended use
☞
To mitigate any performance degradation of a radio equipment under EMC disturbance, system
integration shall adopt appropriate EMC design practice and not contain cables over three meters
on signal and supply ports.
