Smart Module Series
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6.3.2. Reference Circuit Design for Active GNSS 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. Despite its low power consumption, the active antenna
still requires stable and clean power supplies. Therefore, it is recommended to use high-performance
LDO as the power supply. A reference design for active GNSS antenna is shown below.
Active Antenna
3V3
Module
ANT_GNSS
56 nH
10
Ω
1
μF
100 pF
C1
R1
L1
C3
C2
100 pF
R3
R4
R5
0
Ω
NM
NM
Figure 32: Reference Circuit Design for Active GNSS Antenna
It is recommended to use a passive antenna. If active antennas are required, it is strongly recommended
to reserve a
π-type attenuation and ensure that the total gain of the external GNSS RF path of the
module is not greater than 0 dB. At the same time, this may compromise the GNSS performance,
depending on the performance of the active antenna.
6.4. RF Routing Guidelines
For use
r’s PCB, the characteristic impedance of all RF traces should be controlled to 50 Ω. The
impedance of the RF traces is usually determined by the trace width (W), the mat
erials’ dielectric
constant, the height from the reference ground to the signal layer (H), and the spacing between RF
traces and grounds (S). Microstrip or coplanar waveguide is typically used in RF layout to control
characteristic impedance. The following are reference designs of microstrip or coplanar waveguide with
different PCB structures.
NOTE
