Data Sheet
Table Of Contents
- 1 Design guidelines
- 2 Ordering Information
- 3 Pinout and Terminal Descriptions
- 4 Packaging
- 5 Power control
- 6 Interfaces
- 7 Block diagram
- 8 Example schematics
- 9 802.11 Radio
- 10 Firmware
- 11 Host interfaces
- 12 Electrical characteristics
- 13 RF Characteristics
- 14 Physical dimensions
- 15 Layout guidelines
- 16 Soldering recommendations
- 17 Certifications
- 18 Qualified Antenna Types for WF121-E
Silicon Labs
Page 35 of 45
15 Layout guidelines
15.1 WF121-E
RF output can be taken directly from the U.FL connector of the module, and no antenna clearances need to
be made for the module.
15.2 WF121-N
The RF output is taken from the ANT pin at the end of the device. In other variants this pin is not connected.
The antenna trace should be properly impedance controlled and kept short. Figure 6 shows a typical trace
from the RF pin to a SMA connector. A transmission line impedance calculator, such as TX-Line made by
AWR, can be used to approximate the dimensions for the 50 ohm transmission line. Figure 7 show cross
sections of two 50 ohm transmission lines.
Figure 11: Typical 50 ohm trace from the RF pin to an antenna connector