YUGE CLM920 TD3 Usage Manual page 59

CLM920 TD3 LTE Module Hardware Usage Guide
Active antenna power supply VDD needs to match the active antenna of the application, and
it is recommended that customers use LDO/DCDC to power the active antenna, so that when
the GNSS function is not used, the LDO/DCDC can be turned off to reduce the current
consumption.
 The CLM920 TD3 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.
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Figure 3-31 GNSS active antenna reference circuit
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