NORA-W10 series - System integration manual
UBX-22005601 - R04
Design-in
Page 23 of 56
C1-Public
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If the connector’s RF pad size 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
Ω
. 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.
3.2.2.2
Integrated antenna design
If integrated antennas are used, the transmission line is terminated by the integrated antennas
themselves. Follow the guidelines mentioned below:
•
The antenna design process should begin at the start of the whole product design process. Self-
made PCBs and antenna assembly are useful in estimating overall efficiency and 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 large enough according to the related integrated antenna requirements.
The ground plane of the application PCB may be reduced to a minimum size that must be similar
to one quarter of wavelength of the minimum frequency that has to be radiated; however 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 PCB layout and matching circuitry.
•
Further to the custom PCB and product restrictions, antennas may require tuning/matching to
comply with all the applicable required certification schemes. It is recommended to consult the
antenna manufacturer for the design-in guidelines and plan the validation activities on the final
prototypes like tuning/matching and performance measures. See also
•
RF section may be affected by noise sources like hi-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 the interaction between co-located RF systems like LTE sidebands on 2.4 GHz band.
Transmitted power may interact or disturb the performance of NORA-W10 modules.
3.2.3
On-board antenna design
If a plastic enclosure is used, it is possible to use NORA-W10 with the embedded antenna. To reach
optimum operating performance, follow the instructions in this section.
3.2.3.1
NORA-W106
–
PCB trace antenna
•
The module shall be placed in the center of an edge of the host PCB.
A large ground plane on the host PCB is a prerequisite for good antenna performance. It is
recommended to have the ground plane extending at least 10 mm on the three non-edge sides of
the module. See also
•
The host PCB shall include a full GND plane underneath the entire module, with a ground cut out
under the PCB trace antenna according to the description in
•
The NORA-W106 has six extra GND pads under the antenna that need to be connected for a good
antenna performance. Detailed measurements of the footprint including this extra GND pads can
be found in the NORA-W10 series datasheet
•
High / large parts including metal shall not be placed closer than 10 mm to the module’s antenna.
•
At least 10 mm clearance between the antenna and the casing is recommended. If the clearance
is less than 10 mm, the antenna performance can be adversely affected.
