ZOE-M8B - System Integration Manual
UBX-17045131 - R04
Contents
Page 25 of 42
Production Information
Add a ground plane underneath the GNSS SiP to reduce interference. This is especially important
for the RF input line.
For improved shielding, add as many vias as possible around the micro strip/coplanar waveguide,
around the serial communication lines, underneath the GNSS SiP, etc.
Calculation of the micro strip for RF input
The micro strip / coplanar waveguide must be 50
Ω
and be routed in a section of the PCB where
minimal interference from noise sources can be expected. Make sure around the RF line is only
GND as well as under the RF line.
In case of a multi-layer PCB, use the thickness of the dielectric between the signal and the 1st
GND layer (typically the 2nd layer) for the micro strip / coplanar waveguide calculation.
If the distance between the micro strip and the adjacent GND area (on the same layer) does not
exceed 5 times the track width of the micro strip, use the “Coplanar Waveguide” model in AppCad
to calculate the micro strip and not the “micro strip” model.
2.13
Layout
This section provides important information for designing a reliable and sensitive GNSS system.
GNSS signals at the surface of the earth are about 15 dB below the thermal noise floor. Signal loss at
the antenna and the RF connection must be minimized as much as possible. When defining a GNSS
receiver layout, the placement of the antenna with respect to the receiver, as well as grounding,
shielding and jamming from other digital devices are crucial issues and need to be considered very
carefully.
2.13.1
Footprint
Figure 18: Recommended footprint (bottom view)
Symbol
Typ [mm]
e
0.50
g
0.25
f
0.25
D1
4.50
E1
4.50
P
0.27 diameter
Table 4: Footprint dimensions
