RF circuits are very sensitive to power noise, especially burr voltage and other high-frequency harmonics. The microcontroller will suddenly absorb most of the current in a short period of time in each internal clock cycle, because modern microcontroller is manufactured by CMOS process. Therefore, suppose a microcontroller runs at 1MHz's internal clock frequency, it will extract current from the power at this frequency. If no suitable power supply is decoupled, the voltage burr on the power line will be caused. If these voltage burrs reach the power pins of the RF part of the circuit, they may fail to work seriously.