Reference Design Of Rf Layout - Quectel EC2 Series Design Manualline

LTE Standard Module Series
EC2x&EG2x-G Series PCB Design Guideline

3.11.2. 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.
If there is a 2-layer PCB, the top layer is used for signal trace routing, and the bottom layer should be the
reference ground layer, as shown in Figure 32 If there is a 4-layer PCB, the reference ground layer can
be the second, the third, or the fourth layer. If the third layer is selected as the ground layer, the second
layer should be kept out and the width should be at least 5 times the width of the trace，as shown in
Figure 34. The following are reference designs of microstrip and coplanar waveguide with different PCB
structures.
Figure 32: Microstrip Design on a 2-layer PCB
Figure 33: Coplanar Waveguide Design on a 2-layer PCB
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