Smart Module Series
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Figure 37: 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 accurately control the characteristic impedance of RF traces to
50 Ω.
⚫
Design the GND pins adjacent to RF pins as thermal relief pads, and fully connect them to ground.
Keep the distance between the RF pins and the RF connector as short as possible. Change all the
right-angle traces to curved ones and the recommended trace angle is 135°.
⚫
Reserve clearance under the signal pin of the antenna connector or solder joint.
⚫
The reference ground of RF traces should be complete. Meanwhile, ground vias around RF traces
and the reference ground improves RF performance. The distance between the ground vias and RF
traces should be more than two times 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 [3]
5.5. Requirements for Antenna Design
Table 44: Requirements for Antenna Design
Antenna Type
Requirements
GNSS
Frequency range: 1559
–1609 MHz
Polarization: RHCP or linear
VSWR: < 2 (Typ.)
Passive antenna gain: > 0 dBi
Active antenna noise figure: < 1.5 dB
Active antenna gain: > -2 dBi
