Design Notes For Rf Pad Devices - Digi XBee3-PRO Hardware Reference Manual

Hardware
XBee3 Micro keepout area
Notes
1. We recommend non-metal enclosures. For metal enclosures, use an external antenna.
2. Keep metal chassis or mounting structures in the keepout area at least 2.54 cm (1 in) from the
antenna.
3. Maximize the distance between the antenna and metal objects that might be mounted in the
keepout area.
4. These keepout area guidelines do not apply for surface-mount embedded antennas or external
RF connectors.

Design notes for RF pad devices

The RF pad is a soldered antenna connection. The RF signal travels from the RF pad connection (pad
33 on micro modules and pad 36 on surface-mount modules) on the device to the antenna through an
RF trace transmission line on the PCB. Any additional components between the device and antenna
violates modular certification. The controlled impedance for the RF trace is 50 Ω.
We recommend using a microstrip trace, although you can also use a coplanar waveguide if you need
more isolation. A microstrip generally requires less area on the PCB than a coplanar waveguide. We do
not recommend using a stripline because sending the signal to different PCB layers can introduce
matching and performance problems.
Following good design practices is essential when implementing the RF trace on a PCB. Consider the
following points:
Minimize the length of the trace by placing the RPSMA jack close to the device.
n
Connect all of the grounds on the jack and the device to the ground planes directly or through
n
closely placed vias.
XBee3™ RF Module Hardware Reference Manual
Design notes
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