How to locate the noise source of EPS radiated emissions?

During the EPS R&D or rectification phase, using near-field probes to locate radiated emission (RE) noise sources is an efficient method. The location steps are as follows:

1. Preparation and Setup: With the EPS operating normally, connect a near-field probe to a spectrum analyzer, starting from known out-of-range frequencies.

2. Magnetic Field Probe Scan (Applicable to Current Loops): Use a magnetic field probe close to the PCB, components, cables, and gaps to scan for points with the strongest magnetic field strength. These points typically correspond to high di/dt current loops, such as switching transistors, diodes, power inductors, and their pin loops.

3. Electric Field Probe Scan (Applicable to High Voltage Points): Use an electric field probe to scan for points with the strongest electric field strength. These points typically correspond to high dv/dt nodes, such as the drain/collector of switching transistors, transformer pins, and ungrounded metal components.

4. Comprehensive Judgment: Based on circuit principles, determine whether the scanned strong points are potential radiation sources. Verify the improvement effect through temporary measures (such as applying copper foil, using ferrite rings, or point grounding) to accurately locate the source.