Recommended Circuit For Active Antenna; Gnss Rf Design Guidelines - Quectel SC690A Series Hardware Design

When the passive antenna is placed far away from the module (that is, the antenna trace is long), it is
recommended to add an external LNA circuit for better GNSS receiving performance, and the LNA
should be placed close to the antenna.

5.2.2.2. Recommended Circuit for Active Antenna

The active antenna is powered by a 56 nH inductor through the antenna's signal path. The common
power supply voltage ranges from 3.3 V to 5.0 V. Although featuring low power consumption, the active
antenna still requires stable and clean power supplies. It is recommended to use high-performance LDO
as the power supply. A reference design of the GNSS active antenna is shown below.
ANT_GNSS
Module
Figure 32: Reference Circuit Design for GNSS Active Antenna
NOTE
When using external active antennas or external LNA circuits, we recommend reserving type π
attenuation networks (R3, R4, R5) to improve GNSS reception performance.

5.2.2.3. GNSS RF Design Guidelines

Improper design of antenna and layout may cause reduced GNSS receiving sensitivity, longer GNSS
positioning time, or reduced positioning accuracy. To avoid these, please 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.
SC690A_Series_Hardware_Design
C3
R2
0R
C4
C5
100 pF
NM
NM
3V3
Active Antenna
R1
C1 C2
10R
1 μF
100 pF
L1
56 nH
R4
R3 R5
Smart Module Series
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