How to locate the source of noise radiated by the concentrator?

When a concentrator's radiated emissions (RE) exceed the limit, quickly and accurately locating the internal noise source is the first step in rectification. The tools used for location include near-field probes, a spectrum analyzer, and a receiver. First, use the receiver to determine the specific frequency point exceeding the limit. Then, with the concentrator powered on, use near-field probes (magnetic and electrical probes) to scan the PCB, cables, and gaps at close range: magnetic probes are sensitive to current loops and can be used to locate the power loop of the switching power supply and clock traces; electrical probes are sensitive to high-voltage points and can be used to locate switching nodes, crystals, etc. Connect the probes to the spectrum analyzer and observe the signal strength at the frequency point exceeding the limit; the location with the highest strength is the main noise source. Common noise sources include: poorly filtered switching power supplies, high-speed digital clocks, long traces or cables acting as antennas, and leakage through gaps in the shielded enclosure. After location, targeted measures can be taken.