Ublox JODY-W1 Series System Integration Manual page 26

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A de-facto standard for SMA connectors implies the usage of reverse polarity connectors (RP-
SMA) on end user accessible Wi-Fi and Bluetooth interfaces to increase the difficulty to replace
the antenna with higher gain versions and exceed regulatory limits.
The following recommendations apply for proper layout of the connector:
• Strictly follow the connector manufacturer's recommended layout. Some examples are provided
below:
SMA Pin-Through-Hole connectors require GND keep-out (that is, clearance, a void area) on all
o
the layers around the central pin up to annular pins of the four GND posts.
U.FL surface mounted connectors require no conductive traces (that is, clearance, a void area)
o
in the area below the connector between the GND land pins.
• In case of connector's RF pin size wider than the microstrip, remove the GND layer beneath the RF
connector to minimize the stray capacitance thus keeping the RF line 50 . For example, the active
pin of UF.L connector must have a GND keep-out (also called "void area") at least on the first inner
layer to reduce parasitic capacitance to ground.
Figure 7: Example of U.FL connector layout
2.2.2.2 Integrated Antenna Design
If integrated antennas are used, the transmission line is terminated by the antennas themselves.
Follow the guidelines mentioned below:
• The antenna design process should start together with the mechanical design of the product. PCB
mock-ups are useful in estimating overall efficiency and radiation path of the intended design
during early development stages.
• 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 down 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 or ferrite sheets as they may
absorb part of the radiated power, shift the resonant frequency of the antenna or affect the
antenna radiation pattern.
UBX-16012621 - R18
C1-Public
JODY-W1 series - System integration manual
Design-in Page 26 of 72