Product Info

LTE Standard Module Series
EC21 Hardware Design
EC21_Hardware_Design 75 / 120
Figure 33: 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 50Ω. 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