Overview Design notes
XBee/XBee-PRO ZigBee RF Modules User Guide 19
Board layout
XBee modules do not have any specific sensitivity to nearby processors, crystals or other PCB components. Other
than mechanical considerations, no special PCB placement is required for integrating XBee radios except for
those with integral antennas. In general, Power and GND traces should be thicker than signal traces and be able
to comfortably support the maximum currents.
The radios are also designed to be self sufficient and work with the integrated and external antennas without the
need for additional ground planes on the host PCB. However, considerations should be taken on the choice of
antenna and antenna location. Metal objects that are near an antenna cause reflections and may reduce the
ability for an antenna to efficiently radiate. Using an integral antenna (like a wire whip antenna) in an enclosed
metal box will greatly reduce the range of a radio. For this type of application an external antenna would be a
better choice.
External antenna positioning guidelines
Position antennas away from metal objects, which can block or reduce transmission distance. These objects can
include:
Metal poles
Metal studs or beams in structures
Metal rods in concrete
Metal enclosures
Vehicles
Elevators
Ventilation ducts
Refrigerators and microwave ovens
Wire whip antenna positioning
For optimal transmission, follow these guidelines for wire whip antennas:
Place the antenna above or away from any metal objects like batteries, tall electrolytic capacitors or metal
enclosures.
Position the antenna straight and perpendicular to the ground plane and/or chassis.
If you need to bend the antenna to fit into a tight space, bend it away from metal and use caution to avoid
weakening the solder joint connecting the antenna to the module.
Note Antenna elements radiate perpendicular to the direction they point. Thus a vertical antenna emits across
the horizon.
Chip antenna positioning
For optimal transmission, follow these guidelines for chip antennas:
Mount the module onto the edge of the PCB.
Place the PCB inside a plastic enclosure (not metal).
Do not place any ground planes or metal objects above or below the module at the antenna location.
Ensure that the ground, power and signal planes immediately below the antenna section are vacant. See the
following drawing for the recommended keepout area.
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