1. Choose a DC-DC converter with a low switching frequency.
2. The input and output lines of the DC-DC converter should be far away from the antenna. Note: all power supplies should also be far away from the antenna.
3. The antenna should be far away from the LCD, especially the FPC of the LCD.
4. The antenna and RF trace should be far away from the main CPU, including the SDRAM and flash. It is recommended to add EMI filters at the high-speed line of the CPU, SDRAM, and flash. 
5. Use the shielding case to cover the CPU, SDRAM, flash, and DC-DC converter.
6. The antenna should be far away from the SIM card.
7. Ensure that the enclosure surrounding the antenna and structural components is not made of metal.
8. As the enclosure and components surrounding the embedded antenna will influence the RF performance, providing the device to the antenna vendor is strongly recommended to optimize antenna performance. Quectel provides the document for your reference.

There are many reasons why you should use a DC/DC converter, but the most common applications are: To match the loads to the power supply

The isolation voltage given in the datasheets is valid for a 1-second flash test only. If an isolation barrier is required for longer or infinite time the Rated Working Voltage has to be used. 

The ARM microcontroller is considered by many, as the most popular microcontroller existing in the world of the digital embedded system. Many industries prefer to make use of ARM microcontrollers because of their many exciting features. With ARM microcontrollers, such industries can easily implement high-performing products. The ARM microcontroller is cost-sensitive and its applications range to sensors, wireless networking, automotive body system, and others.