Quectel FCM561D-P Hardware Design page 43

Figure 14: Coplanar Waveguide Design on a 4-layer PCB (Layer 3 as Reference Ground)
Figure 15: Coplanar Waveguide Design on a 4-layer PCB (Layer 4 as Reference Ground)
To ensure RF performance and reliability, follow the principles below in RF layout design:
⚫ Use an impedance simulation tool to control the characteristic impedance of RF traces to 50 Ω.
⚫
GND pins adjacent to RF pins should not be designed as thermal relief pads, and should be fully
connected to the ground.
⚫
The distance between the RF pins and the RF connector should be as short as possible and all
right-angle traces should be changed to curved ones. The recommended trace angle is 135° .
⚫
There should be clearance under the signal pin of the antenna connector or solder joint.
⚫
The reference ground of RF traces should be complete. In addition, adding some ground vias
around RF traces and the reference ground could help to improve RF performance. The distance
between the ground vias and RF traces should be at least twice the width of RF signal traces (2 ×
W).
⚫
Keep RF traces away from interference sources, and avoid intersection and paralleling between
traces on adjacent layers.
For more details about RF layout, see document [2].
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