User's Guide

7.3.2 Extended X Dimension Recommendation for Good RF Performance
Figure 7.5. Reference Design for Extended X-dimensioned PCB Sizes*
Note: Spaces filled in black represent metal keep-outs on the PCB in the figure above.*
• Required WFM200 portion size is X = 17.5 mm of metal.
• Required board size is Y = 55mm ± 3 mm of metal.
• PCB may be slightly larger to account for PCB edge routing.
• The recommended board width is Y = 55 mm. Board widths up to Y = 65 mm still meet regulatory certifications but will result in
slightly degraded RF performance.
• Board width (Y) smaller than 55 mm will have lower antenna efficiency, more variation in return loss, and may require TX power to
be reduced to meet RF performance specifications.
• If the carrier board width Y < 45 mm, then better RF performance can be achieved if the WFM200 module is shifted to north, i.e.,
ensure larger (close to 22.5 mm) PCB metal width on the antenna clearance area side of WFM200. Otherwise, center pins 49 and
48 vertically.
• Add 3 mm wide keep-outs adjacent to the designated component placement areas near WFM200, which allows only an 18 mm wide
bridge of GND and signal routing area between the two PCB portions.
• The extension in X dimension can be any length.
• The center of pin 49 is 1.8 mm from the metal edge.
• Connectors are only allowed in the X dimension extension portion.
• Components may be placed north and south of the occupied area, but these must be surrounded by GND to the edge of the place-
ment areas.
UG395: WFM200 Hardware Design User's Guide
Layout Recommendations
silabs.com | Building a more connected world. Preliminary Rev. 0.1 | 19