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Hardware Integration Guide
Poor routing
The yellow traces cross the RF trace.
Figure 31.
RF Routing Examples
Fill the area around the RF traces with ground and ground vias to connect inner ground layers
for isolation.
Cut out ground fill under RF signal pads to reduce stray capacitance losses.
Avoid routing RF traces with sharp corners. A smooth radius is recommended.
E.g. Use of 45° angles instead of 90° .
The ground reference plane should be a solid continuous plane under the trace.
The coplanar clearance (G, below) from the trace to the ground should be at least the trace
width (W) and at least twice the height (H). This reduces the parasitic capacitance, which
potentially alters the trace impedance and increases the losses.
E.g. If W = 100 microns then G = 200 microns in an ideal setup. G = 150 microns would also
be acceptable is space is limited.
Figure 32.
Coplanar Clearance Example
Note:
The figure above shows several internal ground layers cut out, which may not be necessary for
every application.
4116922
Correct routing
There is no signal around the RF path.
Rev 1.1
Routing Constraints and
Recommendations
January 21, 2015
53
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