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 36 of 45
FR4,
ε
r
= 4.6
Prepreg, ε
r
= 3.7
W = 0.15 mm
h = 0.076 mm
G = 0.25 mm
GND stitching vias
RF GROUND
RF GROUND RF GROUND
RF GROUND
FR4, ε
r
= 4.6
h = 1 mm
W = 1.8 mm
MICROSTRIP
CPW Ground
Figure 12: Example cross section of two different 50 ohm transmission line
15.3 WF121-A
Figure 13: Example layouts, board edge placement on left, board corner on right
The impedance matching of the antenna is designed for a layout similar to the module evaluation board. For
an optimal performance of the antenna the layout should strictly follow the layout example shown in the above
figures and the thickness of FR4 should be between 1 and 2 mm, preferably 1.6mm.
Any dielectric material close to the antenna will change the resonant frequency and it is recommended not to
place a plastic case or any other dielectric closer than 5 mm from the antenna. Close proximity of a plastic
case can be somewhat compensated by using a thinner PCB.