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CLM920 TD3 LTE Module Hardware Usage Guide
3.19.2 Diversity antenna interface
The 35-pin of the CLM920 TD3 is a diversity antenna interface. To facilitate antenna
debugging, a π-type matching circuit needs to be added to the main board, and a 50-ohm
impedance line is required. The main antenna and the diversity antenna need to maintain a
certain spacing. The recommended circuit is as shown below：
3.19.3 GNSS interface
The 47 pin of the CLM920 TD3 is a GNSS antenna interface. It supports GPS, BEIDOU,
GLONASS, and GALILEO signal reception. If you need to use it, you need to use the AT
command AT+CGPS=1 to turn on the GPS (for details, please refer to the CLM920 TD3 AT
command set manual) In order to facilitate the debugging of the antenna, it is necessary to add
a π-type matching circuit to the main board, and take a 50-ohm impedance line. The GNSS
antenna needs to maintain a certain distance from the main antenna and the diversity antenna.
The GNSS antenna has two antenna connection modes, and the other is a connection. Passive
antenna, the other is to connect the active antenna. Since the module itself cannot supply
power to the GNSS active antenna, it needs to be externally provided. The recommended
circuit is as shown below：
The figure below shows L5 in the active antenna matching circuit. L6 is not attached by
default. C5 is affixed to 100pF by default. The specific value is provided by the antenna
factory after the antenna is debugged. C6 defaults to 100pF, which is a DC blocking capacitor.
Shanghai Yuge Information Technology co., LTD
Figure 3-29 Diversity Antenna Matching Circuit
Figure 3-30 GNSS passive antenna reference circuit
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