The generation of EMI is caused by the electromagnetic interference source transmitting energy to the sensitive system through the coupling path. It includes three basic forms: conduction via wire or common ground, radiation through space, or near-field coupling. The hazard of EMI is manifested in reducing the quality of the transmission signal, causing interference or even damage to the circuit or equipment, making the equipment unable to meet the technical index requirements specified by the electromagnetic compatibility standard.
In order to suppress EMI, the EMI design of digital circuits should be carried out according to the following principles:
●According to the relevant EMC/EMI technical specifications, the indicators are decomposed into single-board circuits and controlled at different levels.
●Control from the three elements of EMI, namely, interference source, energy coupling path and sensitive system, so that the circuit has a flat frequency response and ensures the normal and stable operation of the circuit.
●Start with the front-end design of the equipment, pay attention to the EMC/EMI shielding scheme design, and reduce the design cost.