How should the onboard filters of the PCS (Power Control System) and the cabinet filters be coordinated?

The onboard filters and cabinet filters of the PCS need to work together to form a hierarchical defense system. Onboard filters (such as decoupling capacitors, small ferrite beads, and surface-mount common-mode inductors near power modules) are responsible for the first attenuation at the noise source, suppressing the generation and spread of high-frequency noise within the board. Cabinet filters (independent EMI filtering modules) handle the noise remaining after onboard filtering and external interference introduced through cables, providing high attenuation at the system level to meet standard limits.

Key points for coordination:

1. Impedance matching: The output impedance of the onboard filter should be higher, and the input impedance of the cabinet filter should be lower, creating a mismatch to improve overall isolation.

2. Frequency division: The onboard filter focuses on suppressing VHF noise >10MHz, while the cabinet filter focuses on mid-to-low frequency noise <10MHz.

3. Grounding coordination: Both should be connected to the same low-impedance "clean ground" reference point.

4. Cable handling: Cables entering the cabinet must be shielded, and the shielding layer should be grounded with a 360-degree overlap at the filter entrance.