Hangzhou Tuya Inc.
NM1 Module Hardware Design Manual
https://www.tuya.com
Page 23 of 29
Figure 4- 2 Antenna PCB cabling impedance calculation data
4.3.2 Precautions for Initial Antenna Design
4.3.2.1 Pre-project Evaluation
Ensure that the antenna is horizontal with the base station for maximum efficiency. Do not place the antenna
near the power cable, data cable, or chip that may generate electromagnetic interference. Do not reserve a
place for hands on the antenna to prevent attenuation caused by the human body. Consider radiation reduction
and structure implementation. In the initial design phase, the structure, ID, circuit, and antenna engineers
evaluate the antenna layout together.
4.3.2.2 Antenna Matching Circuit
If a long cable exists between the RF and antenna interfaces on the NM1 module, design 50 ohms
characteristics impedance for the microstrip or stripline between the RF pad and the antenna interface during
PCB circuit design. In addition, reserve a matching circuit.
4.4 Suggestions on EMC and ESD Design
During overall design, consider EMC issues related to signal integrity and power integrity. During peripheral
circuit cabling of the NM1 module, reserve doubled trace width between the power cable and signal cable to
reduce signal coupling and ensure pure return current. During peripheral power circuit design, place the
decoupling capacitor near the power pin on the NM1 module, keep high-frequency and high-speed circuits and
sensitive circuits away from the PCB edges, and isolate the circuits from each other to reduce interference.
Protect sensitive signals, and shield circuits or components on the PCB that may interfere the NM1 module.
Consider ESD protection during design. Place ESD components near the key input and output signal interfaces,
for example, the SIM card signal interface, to protect them. On the PCB, reasonably design mechanical parts and
PCB layout and ensure proper grounding of metal shielding covers to provide a smooth channel for static
electricity discharging.
4.5 PCB Solder Pad Design
You are advised to design the middle 14 pads on the PCB based on the sizes in the structure diagram. Externally
extend the 52 signal pads around the PCB to the NM1 module for over 0.3 mm, and externally extend other three
sides of the pads for 0.05 mm. Use 50 ohms impedance cables for the main antenna and Wi-Fi antenna.
4.6 Thermal Design
The NM1 module generates heat when it works and may be affected by other high-temperature components. The
NM1 module design ensures good heat dissipation. When connecting the NM1 module to the PCB, properly
connect the thermal pad to the ground to ensure thermal conduction and balance and a better electrical
performance.
Note:
1. Place the NM1 module away from the power supply and high-speed signal cables, and protect these cables.
