NINA-B1 series - System integration manual
UBX-15026175 - R16
Design-in
Page 38 of 63
C1-Public
o
FR-4 material exhibits poor thickness stability and thus less control of impedance over the
trace length. Contact the PCB manufacturer for specific tolerance of controlled impedance
traces.
•
The transmission lines width and spacing to GND must be uniform and routed as smoothly as
possible: route RF lines in 45 ° angle or in arcs.
•
Add GND stitching vias around transmission lines.
•
Ensure solid metal connection of the adjacent metal layer on the PCB stack-up to main ground
layer, providing enough vias on the adjacent metal layer.
•
Route RF transmission lines far from any noise source (as switching supplies and digital lines) and
from any sensitive circuit to avoid crosstalk between RF traces and Hi-impedance or analog
signals.
•
Avoid stubs on the transmission lines, any component on the transmission line should be placed
with the connected pad over the trace. Also avoid any unnecessary component on RF traces.
Figure 28: Example of RF trace and ground design from LILY-W1 Evaluation Kit (EVK)
3.3.2
Antenna design (NINA-B111 only)
Designers must take care of the antennas from all perspective at the beginning of the design phase
when the physical dimensions of the application board are under analysis/decision as the RF
compliance of the device integrating NINA-B1 module with all the applicable required certification
schemes heavily depends on the radiating performance of the antennas. The designer is encouraged
to consider one of the u-blox suggested antenna part numbers and follow the layout requirements.
•
External antennas such as linear monopole:
o
External antennas basically do not imply physical restriction to the design of the PCB where
the module is mounted.
o
The radiation performance mainly depends on the antennas. It is required to select antennas
with optimal radiating performance in the operating bands.
o
RF cables should be carefully selected with minimum insertion losses. Additional insertion loss
is introduced by a low quality or long cable. Large insertion loss reduces radiation performance.
o
A high quality 50
Ω
coaxial connector provides proper PCB-to-RF-cable transition.
•
Integrated antennas such as patch-like antennas:
o
Internal integrated antennas imply physical restriction to the PCB design:
Integrated antenna excites RF currents on its counterpoise, typically the PCB ground plane of the
device that becomes part of the antenna; its dimension defines the minimum frequency that can
be radiated. Therefore, the ground plane can be reduced to a minimum size that should be similar
to the quarter of the wavelength of the minimum frequency that has to be radiated, given that the
orientation of the ground plane related to the antenna element must be considered.
