MAX-7 / NEO-7 - Hardware Integration Manual
UBX-13003704
-
R09
Production Information
Product
handling
Page
44 of 52
For robustness, EOS protection measures, as shown in the examples in Figure 33, are recommended for designs
combining cellular communication transceivers (e.g. GSM, GPRS) and GNSS receivers 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
P
S
R
e
c
e
iv
e
r
LNA
GPS
Bandpass
Filtler
E
RF
_
IN
G
P
S
R
e
c
e
iv
e
r
L
GPS
Bandpass
Filtler
F
LNA with appropriate ESD
rating and maximum input
power
GPS Band pass Filter: SAW or
Ceramic with low insertion loss
and appropriate ESD rating
Figure 33: EOS and ESD Precautions
7.3.6
Electromagnetic interference (EMI)
Electromagnetic interference (EMI) is the addition or coupling of energy originating from any RF emitting device.
This can cause a spontaneous reset of the GNSS receiver or result in unstable performance. Any unshielded line
or segment (>3mm) connected to the GNSS receiver can effectively act as antenna and 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 (e.g. R>20
) or better yet a ferrite bead
(BLM15HD102SN1) or an inductor (LQG15HS47NJ02) into any unshielded PCB lines connected to the GNSS
receiver. Place the resistor as close as possible to the GNSS receiver pin.
Example of EMI protection measures on the RX/TX line using a ferrite bead:
TX
RX
G
P
S
R
e
c
e
iv
e
r
FB
FB
BLM15HD102SN1
>10mm
Figure 34: EMI Precautions
