It is quite common to encounter RFI or radio frequency interference in various electrical and electronic equipment like work processors, business computing devices, industrial controls, electronic printers, personal computers and many more. Some components like relays, switching power supplies, motors etc are also known to produce RFI.
Basically RFI is unwanted electromagnetic energy in the frequency range primarily used for radio communication. People are concerned with RFI mainly because of two reasons. Firstly, to ensure the proper operation of equipment in application environment and secondly, to ensure no interference in RF communication with production of RFI which often put health and safety at stake.
The necessity of reliable RF communication has also given rise to legal regulations for effective RFI control for electronic equipment. The rescue object here is the power line filter. These filters act as the main tool to control RFI both into the equipment and also out of it.
In the fast developing world, more and more electrical energy is being generated with high powers where an excessive amount of low power energy is being used for the transmission as well as processing of data. It results in increased production of noise and interference which can even destroy electronic devices if not controlled by power line filters.
A power line filter is a multi-port network of passive components that are arranged inside the filter as a dual low-pass. One network is used for common mode attenuation while another one is used for differential mode attenuation.
The working of power line filters is slightly complex. These filters act as a passive bilateral network and have complex transfer characteristics, dependent strictly upon source and load impedance. Their function mainly is to trap noise or prevent it from entering or leaving the electrical equipment. RFI goes through a power line in two modes - asymmetric or common mode and symmetric or differential mode. Filters attenuate the RFI to pass through with negligible or no attenuation.
RFI makes it impossible to work under certain conditions and use electrical devices. They also impose health and safety risks so they must be removed from the electrical equipment being used. It is not like that these interferences cannot be controlled but adequate procedures and devices must be used in order to get the desired results. RFI can easily be controlled by providing proper shielding in the enclosure of the equipment. The filter effectively suppresses the conducted noise reducing the level of RFI within the level of acceptance.
