Wi-Fi&Bluetooth Module Series
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3.8.4. Reference Design of RF Layout
Figure 9: Microstrip Design on a 2-layer PCB
Figure 10: Coplanar Waveguide Design on a 2-layer PCB
Figure 11: Coplanar Waveguide Design on a 4-layer PCB (Layer 3 as Reference Ground)
For user’s PCB, the characteristic impedance of all RF traces should be controlled to 50 Ω. The
impedance of the RF traces is usually determined by the trace width (W), the materials’ dielectric constant,
the height from the reference ground to the signal layer (H), and the spacing between RF traces and
grounds (S). Microstrip or coplanar waveguide is typically used in RF layout to control characteristic
impedance. The following are reference designs of microstrip or coplanar waveguide with different PCB
structures.
