How can onboard and external filters in a power line carrier PLC work together?

The onboard and external filters of the power line carrier PLC need to work together to form a complementary filtering system. The onboard filter targets chip-level noise by deploying decoupling capacitors (100nF + 10μF) and PBZ1608A-102Z0T ferrite beads at the power pins to suppress high-frequency noise. The external filter addresses system-level interference by installing an EMI filter at the power line inlet, including a common-mode inductor CML4532A-510T and safety capacitors. In the collaborative design, impedance matching must be considered: the external filter provides high impedance in the low-frequency range (<1MHz), while the onboard filter provides low impedance in the high-frequency range (>10MHz), forming a wideband filter. The overall frequency response is optimized through simulation to ensure attenuation greater than 40dB in the 10kHz-1GHz range. In the actual layout, the external and onboard filters are connected via jumpers to reduce lead inductance. During conducted emission testing, the combined effect of the two filters ensures the system meets the EN55032 Class B limit with a margin greater than 6dB.