Gnss Rf Design Guidelines - Quectel SC200L-EM Hardware Design

5.2 GNSS RF Design Guidelines

Bad design of antenna and layout may cause reduced GPS receiving sensitivity, longer GPS positioning
time, or reduced positioning accuracy. In order to avoid this, please follow the reference design rules as
below:
6 Maximize the distance between the GNSS RF part and the GPRS RF part (including trace routing
and antenna layout) to avoid mutual interference.
7 In user systems, GNSS RF signal lines and RF components should be placed far away from
high-speed circuits, switched-mode power supplies, power inductors, the clock circuit of single-chip
microcomputers, etc.
8 For applications with a harsh electromagnetic environment or with high requirement on ESD
protection, it is recommended to add ESD protection diodes for the antenna interface. Only diodes
with ultra-low junction capacitance such as 0.5pF can be selected. Otherwise, there will be effects
on the impedance characteristic of the RF circuit loop or attenuation of the bypass RF signal may be
caused.
9 Control the impedance of either feeder line or PCB trace to 50Ω, and keep the trace length as short
as possible.
10 Refer to Chapter 6.3 for the GNSS reference circuit design.
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