How to locate the radiated noise source of the motion controller MC?

Identifying the radiated noise source of the motion controller MC is a prerequisite for rectifying excessive radiated emissions. A near-field probe kit, including magnetic and electric field probes, is used for scanning.

First, the excessive frequency point is determined during testing in an anechoic chamber or open field. Then, with the module powered on, the near-field probes are used to scan the PCB surface, chips, cables, connectors, and gaps at close range. The intensity change of the signal at that frequency point is observed on a spectrum analyzer; the location with the strongest signal is the main radiation source or leakage point. Magnetic field probes are sensitive to current loops and are suitable for locating switching power supply loops or clock traces; electric field probes are sensitive to voltage changes and are suitable for locating chip pins or unshielded conductors. Using an oscilloscope, time-domain waveforms can be observed. After locating the problem area, targeted measures can be taken, such as adding shielding to chips, adding filtering to traces, improving cable shielding grounding, and adding conductive pads to gaps. Near-field localization is a key tool for efficient rectification.