LiSn

Line Impedance Stabilization Network (LISN) is a device used in electromagnetic compatibility (EMC) testing to provide a defined impedance on the power line for conducted emissions measurements and to isolate the equipment under test (EUT) from the measurement instrument. The LISN is placed between the mains supply and the EUT, so that RF energy generated by the EUT is directed toward the measurement port rather than back into the power supply. This arrangement helps achieve repeatable measurements by stabilizing the RF impedance seen by the EMI receiver.

A typical LISN includes a radio frequency filter network and a 50-ohm measurement port connected to an EMI receiver. The EUT is powered from the LISN’s line and neutral connections, while earth or protective grounding may be connected to the EUT as required by the test setup. The LISN presents a specified impedance to the EUT over a defined RF frequency range, commonly from about 9 kHz to 30 MHz, enabling the conversion of conducted emissions into a measurable voltage on the 50-ohm port. In many tests, separate LISN units are used on both the line and the neutral conductors, providing individual measurement ports with a shared reference to earth.

LISNs are specified by EMC standards such as CISPR 16 and EN 55022/55032. They require proper calibration and adherence to defined impedance and grounding requirements to ensure accuracy and reproducibility. Limitations include the narrow RF frequency range, tolerance in impedance, and the need for careful setup to avoid introducing additional RF paths. LISNs are essential for standardized conducted-emission measurements and comparability across laboratories.

See also: electromagnetic compatibility, conducted emissions, CISPR, EN 55022.