Texas Instruments WL1835MODCOM8B, User Manual

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Layout Guidelines
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20 SWRU359E – September 2013 – Revised September 2015
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WL1835MODCOM8B WLAN MIMO and Bluetooth
®
Module EVM
Figure 20. Trace Design for the PCB Layout
Figure 21 shows layer 1 with the trace to the antenna over ground layer 2.
Figure 21. Layer 1 Combined With Layer 2
Table 4 , Figure 22 , and Figure 23 describe instances of good layout practices for the antenna and RF
trace routing.
Table 4. Antenna and RF Trace Routing Layout Guidelines
Reference Guideline Description
1
The RF trace antenna feed must be as short as possible beyond the ground reference. At this point, the trace
starts to radiate.
2
The RF trace bends must be gradual with an approximate maximum bend of 45 degrees with trace mitered. RF
traces must not have sharp corners.
3 RF traces must have via stitching on the ground plane beside the RF trace on both sides
4 RF traces must have constant impedance (microstrip transmission line).
5
For best results, the RF trace ground layer must be the ground layer immediately below the RF trace. The
ground layer must be solid.
6 There must be no traces or ground under the antenna section.
7
RF traces must be as short as possible. The antenna, RF traces, and modules must be on the edge of the PCB
product. The proximity of the antenna to the enclosure and the enclosure material must also be considered.