Reference Design Of Rf Layout - Quectel FC21 Hardware Design

Wi-Fi&BT Module Series
FC21 Hardware Design
FC21
R1
RF_ANT
0R
C2
C1
NM
NM
Figure 11: Reference Circuit for RF Antenna Interface
Another type of reference circuit for the RF antenna interface is shown below. It is designed for vehicle
applications. It is recommended to reserve two notch filter circuits and a π-type matching circuit for better
RF performance. C2/L1 and L3/C3 comprise two notch filter circuits for filtering out interference caused by
a particular frequency. When L3/C2/L1/C3 is NC, C1/L2/C4 comprise a π-type matching circuit.
Capacitors C1/C2/C3/C4 and inductors L1/L3 are not mounted by default, and L2 is 0Ω by default.
Figure 12: Reference Circuit for RF Antenna Interface (Vehicle Applications)

3.7.4. Reference Design of RF Layout

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.
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