Quectel Smart LTE Module Series Hardware Design page 91

Figure 36: Coplanar Waveguide Line Design on a 4-layer PCB (Layer 3 as Reference Ground)
Figure 37: Coplanar Waveguide Line Design on a 4-layer PCB (Layer 4 as Reference Ground)
In order to ensure RF performance and reliability, the following principles should be complied with in RF
layout design:

Use impedance simulation tool to control the characteristic impedance of RF traces as 50Ω.

The GND pins adjacent to RF pins should not be designed as thermal relief pads, and should be fully
connected to ground.

The distance between the RF pins and the RF connector should be as short as possible, and all the
right-angle traces should be changed to curved ones.

There should be clearance area under the signal pin of the antenna connector or solder joint.

The reference ground of RF traces should be complete. Meanwhile, 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 no less than two times the width of RF signal traces (2*W).
For more details about RF layout, please refer to document [3].
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