Integration Manual

NORA-B1 series - System integration manual
UBX-20027617 - R04 Design-in Page 29 of 61
C1-Public
Consider that SMT connectors are typically rated for a limited number of insertion cycles. In
addition, the RF coaxial cable may be relatively fragile compared to other types of cables. To
increase application ruggedness, connect the U.FL connector to a more robust connector such as
SMA fixed on panel.
☞ A de-facto standard for SMA connectors implies the usage of reverse polarity connectors (RP-
SMA) on Wi-Fi and Bluetooth end-products. The standard makes it more difficult for the end
users to replace the antenna with higher gain versions and exceed the regulatory limits.
Observe these recommendations for proper layout of the connector:
• Strictly follow the connector manufacturer’s recommended layout:
o SMA Pin-Through-Hole connectors require GND keep-out (that is, clearance, a void area) on
all the layers around the central pin up to annular pads of the four GND posts.
o U.FL surface mounted connectors require no conductive traces (that is, clearance, a void
area) in the area below the connector between the GND land pads.
• If the RF pad size of the connector is wider than the micro strip, remove the GND layer beneath
the RF connector to minimize the stray capacitance thus keeping the RF line 50 . For example,
the active pad of the U.FL connector must have a GND keep-out (that is, clearance, a void area),
at least on the first inner layer to reduce parasitic capacitance to ground.
4.3.2.2 Integrated antenna design
The following guidelines should be followed when integrating an antenna onto the host PCB:
• Antenna integration should begin at the start of the end-product design process. Self-made
PCBs and antenna assemblies are useful in estimating overall efficiency and the radiation path
of the intended design.
• Use antennas designed by an antenna manufacturer providing the best possible return loss (or
VSWR).
• Provide a ground plane that is large enough to meet the related integrated antenna
requirements. The ground plane of the application PCB can be reduced to a minimum size of one-
quarter wavelength of the minimum frequency that needs to be radiated, although overall
antenna efficiency may benefit from larger ground planes.
• Proper placement of the antenna and its surroundings is also critical for antenna performance.
Avoid placing the antenna close to conductive or RF-absorbing parts such as metal objects,
ferrite sheets and so on as they may absorb part of the radiated power or shift the resonant
frequency of the antenna or affect the antenna radiation pattern.
• It is highly recommended to strictly follow the detailed and specific guidelines provided by the
antenna manufacturer regarding correct installation and deployment of the antenna system,
including the PCB layout and matching circuitry.
• In addition to the custom PCB and product restrictions, antennas may require tuning/matching
to comply with all the applicable required certification schemes. It is advisable to consult the
design-in guidelines of the antenna manufacturer and plan the validation activities on the final
prototypes, like tuning/matching and taking performance measurements. See also Table 11.
• The RF section may be affected by noise sources like high-speed digital buses. Avoid placing the
antenna close to buses such as DDR or consider taking specific countermeasures like metal
shields or ferrite sheets to reduce the interference.
⚠ Take care of interaction between co-located RF systems like LTE sidebands on 2.4 GHz band.
Transmitted power may interact or disturb the performance of NORA-B1 modules.