Rf Transmission Line Design (Nora-B101 Only) - Ublox NORA-B1 Series System Integration Manual

• NORA-B101 modules include an ANT pad for connecting an external antenna. The antenna can be
either an external SMD antenna or an antenna that is connected through an externally assembled
U.FL or RP-SMA connector.
o
Antennas with SMD connections, either reverse-polarity SMA connectors or U.FL connectors,
must be radio tested and verified against regulatory FCC, IC, RED, and MIC standards.
• NORA-B106 modules include an embedded PCB antenna. See section 4.3.3 for design-in
information. NORA-B106 cannot be mounted inside a metal enclosure. Similarly, the physical
casing accommodating these modules must not be fabricated in metal or any plastic that includes
metal flakes, metallic based paint, carbon black, or lacquer.
⚠
According to FCC regulations, the transmission line from the module antenna pin to the antenna
(or antenna connector) on the host PCB is considered part of the approved antenna design.
Consequently, module integrators must follow exactly one of the antenna reference designs used
in the module during FCC type approval – or certify their own designs.
4.3.1

RF transmission line design (NORA-B101 only)

RF transmission lines like those from the ANT pad up to the related antenna connector, or up to the
related internal antenna pad, must be designed so that the characteristic impedance is as close as
possible to 50 Ω. Tolerances of ±5 Ω are commonly specified. Figure 4 shows the design options and
the parameters that must be considered when implementing a transmission line on a PCB, where:
•
Micro strip is a track coupled to a single ground plane, separated by dielectric material.
•
Coplanar micro strip is a track coupled to ground plane and side conductors, separated by
dielectric materials.
•
Stripline is a track sandwiched between two parallel ground planes and separated by dielectric
materials.
Figure 4: Transmission line trace design
To design a 50 Ω transmission line properly, consider the following points:
•
Designers should provide enough clearance from the surrounding traces and ground plane in the
same layer. Consider a trace-to-ground clearance that is at least twice the width of the trace, and
make sure that the transmission line is "guarded" by the ground plane area on each side.
UBX-20027617 - R02
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NORA-B1 series - System integration manual
Design-in Page 22 of 58