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RF LAYOUT CONSIDERATIONS 6
PCB Considerations
The minimum implementation is a two-layer PCB substrate with all the RF signals on
one side and a solid ground plane on the other. Multilayer boards can also be used.
Two possible RF transmission line topologies include microstrip and stripline.
Microstrip Transmission Lines
Figure 6.1
Microstrip Transmission Lines
Ground Plane Design Recommendation
Use a complete ground plane immediately under the PCB layer on which the
Copernicus module is mounted. Around the signal tracks on the same layer as the
module, flood or “copper pour” and connect to the ground plane using low inductance
vias. A single ground plane is adequate for both analog and digital signals.
Design of Microstrip Transmission Line
Connections to either the LNA output or to a passive antenna must be made using a
50 ohm unbalanced transmission system. The PCB parameters that affect impedance
are:
• Track width (W)
• PCB substrate thickness (H)
• PCB substrate permittivity (ε r )
Copernicus GPS Receiver 73