
CLM920_NC3_LTE Module hardware manual
Shanghai Yuge Information Technology co., LTD
- 54 -
The CLM920 NC3 module provides three RF antenna interfaces, which are the main set
antenna, the diversity antenna and the GPS antenna connection port. The antenna
interface must be a 50 ohm characteristic impedance trace.
In actual use, according to the user's circuit board routing, the antenna factory debugs and
optimizes the matching device parameter values. The motherboard C1/C2/C3/C4/C5/C6
defaults to 100pF, L1/L2/L3/L4/L5/L6 defaults to empty. In order to prevent static
damage to the internal part of the module, it is recommended to attach a bidirectional
TVS tube at the antenna connection D1/D2/D3.
The parasitic capacitance of the TVS tube pins themselves must be small to avoid signal
interference. The ESD protection component used on the antenna must take into account
the frequency band used by the antenna and the minimum parasitic capacitance that can
be accepted by different frequency bands. The ESD protection component usually used
on the antenna must have a parasitic capacitance value of less than 0.5pF or even more.
low.
Antenna impedance traces need to be away from digital signal lines, power supplies and
other interference signals.
The antenna impedance traces need to be three-dimensionally packaged, and the ground
holes are added on both sides of the trace to isolate.
3.17.4 RF trace reference
For the user, the characteristic impedance of all RF signal lines should be controlled at
50
Ω
. The impedance of the RF signal line is determined by the dielectric constant of the
material, the trace width (W), the ground clearance (S), and the height of the reference ground
plane (H). Please use the impedance simulation tool to calculate the impedance value of the
RF trace. The control of the PCB characteristic impedance is usually in the form of microstrip
lines and coplanar waveguides.