LTE Module Series
EG21-G Hardware Design
EG21-G_Hardware_Design 58 / 100
5.1.3.
Reference Design of RF Antenna Interface
A reference design of ANT_MAIN and ANT_DIV antenna pads is shown as below. A π-type matching
circuit should be reserved for better RF performance. The capacitors are not mounted by default.
ANT_MAIN
R1 0R
C1
Module
Main
Antenna
NM
C2
NM
R2 0R
C3
Diversity
Antenna
NM
C4
NM
ANT_DIV
Figure 30: Reference Circuit of RF Antenna Interface
1.
Keep a proper distance between the main antenna and the Rx-diversity antenna to improve the
receiving sensitivity.
2.
ANT_DIV
function is enabled by default.
AT+QCFG="diversity",0
command can be used to disable
receive diversity.
Please refer to
document [2]
for details.
3.
Place the
π-type matching components (R1&C1&C2, R2&C3&C4) as close to the antenna as
possible.
5.1.4.
Reference Design of RF Layout
For user’s PCB, the characteristic impedance of all RF traces should be controlled as 50
Ω
. The
impedance of the RF traces is usually determined by the trace width (W), the materials’ dielectric constant,
height from the reference ground to the signal layer (H), and the space between the RF trace and the
ground (S). Microstrip and coplanar waveguide are typically used in RF layout to control characteristic
impedance. The following figures are reference designs of microstrip or coplanar waveguide with different
PCB structures.
NOTES
