Digi XBee3-PRO Hardware Reference Manual page 25

Hardware
Space any ground fill on the top layer at least twice the distance d, for Micro modules at least
n
0.028" and for surface mount modules at least 0.050".
Additional considerations:
The top two layers of the PCB have a controlled thickness dielectric material in between.
n
The second layer has a ground plane which runs underneath the entire RF pad area. This
n
ground plane is a distance d, the thickness of the dielectric, below the top layer.
The RF trace width determines the impedance of the transmission line with relation to the
n
ground plane. Many online tools can estimate this value, although you should consult the PCB
manufacturer for the exact width.
Implementing these design suggestions helps ensure that the RF pad device performs to its
specifications.
The following figures show a layout example of a host PCB that connects an RF pad device to a right
angle, through-hole RPSMA jack.
Number Description
Maintain a distance of at least 2 d between microstrip and ground fill.
1
XBee3™ RF Module Hardware Reference Manual
Design notes
25