The primary function of signal line filters is to address spatial electromagnetic interference issues, such as equipment emitting strong electromagnetic interference into space or being sensitive to space-based electromagnetic interference. The coupling between signal line cables and power line cables previously observed, which results in excessive conducted emissions at high frequencies, is due to high-frequency interference on the signal line coupling into the power line via space. This phenomenon occurs because the signal cable itself acts as an efficient radiating and receiving antenna, and the的危害 includes:

1) Causing Strong Excessive Radiation: Electromagnetic energy within the housing induces common-mode voltage and current on the cables, with the common-mode current flowing through the cables, resulting in common-mode radiation. This type of radiation is often the primary cause of excessive radiation from the equipment.

2) Upon reception of electromagnetic energy in the surrounding space of the equipment by the cables, it forms common-mode current, which travels along the wires into the housing. This not only interferes with circuits directly connected to the cables but also, through the wires, re-radiates, causing interference to other circuits within the housing that are not directly connected to the cables.

3) The destruction of shielding or isolation layers is caused by the cable's reception and re-radiation of electromagnetic waves, leading to the leakage of electromagnetic energy through the cable. This can be observed as a decrease in the shielding effectiveness of the shielding layer.