Analysis of electromagnetic interface filters for power systems and telephone lines

EMI consists of any unwanted, spurious, conducted, or radiated signals of electrical origin that can cause degradation in equipment performance. Because of these problems, all components must comply with specifications to ensure electromagnetic compatibility (EMC), and there are numerous design methods that can be used to prevent EMI. An EMI source can be any device that transmits, distributes, processes, or utilizes any form of electrical energy where some aspect of its operation generates conducted or radiated signals that can cause equipment performance degradation. When induction is suspected, there are several approaches to mitigation. Cabling can be replaced with more effectively shielded types. In cases where the substitution of special cabling with a shielded type is not possible, rerouting or increasing the distance between cable bundles may offer a solution. Interference by conduction can usually be reduced or eliminated by a careful analysis of wiring routing and connections, including potential loops existing between electrically powered beds or other devices and the affected equipment. Adding filters to inputs and power sources is another possible solution. This paper describes some EMI filters that can be used to remove noise in powerline and telephone lines.