Smart Module Series
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5.2. GNSS RF Design Guidelines
Bad design of antenna and layout may cause reduced GNSS receiving sensitivity, longer GNSS
positioning time, or reduced positioning accuracy. In order to avoid this, follow the reference design rules
as below:
⚫ Maximize the distance between the GNSS RF part and the GPRS RF part (including trace routing
and antenna layout) to avoid mutual interference.
⚫ In user systems, place GNSS RF signal lines and RF components far away from high-speed circuits,
switch-mode power supplies, power inductors, the clock circuit of single-chip microcomputers, etc.
⚫ For applications with harsh electromagnetic environment or high ESD-protection requirements, it is
recommended to add ESD protective diodes for the antenna interface. The junction capacitance of
the diodes should be less than 0.5 pF. Otherwise, it will influence the impedance characteristic of RF
circuit loop, or cause attenuation of bypass RF signals.
⚫ Control the impedance of feeder lines and PCB traces to 50 Ω, and keep the trace as short as
possible.
⚫ See Chapter 6.3 for reference circuit designs of GNSS antenna.
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