LISN is short for Line Impedance Stabilization Network. LISN is important assistant equipment for EMC test in the power system. It can isolate the disturbance from power grid, provide stability test impedance and pay the role of filtering wave.
LISN net is based on filter theory. When spectrum interference is different from the useful signal band, filter out the unwanted signal by filter. Proper design and selection and correct use of filter is the key to realize the function of LISN.
LISN is in EMI test, in order to objectively assess the interference of the equipment under test (EUT), add the net between the power grid and tested objects. The net has the following functions:
1. Provide prescribed stability impedance in the specified frequency range. Because the power network is affected by various factors, make the line impedance instability. However, in the conduction interference measurement, impedance is very important. In order to have a uniform test conditions in the conducted emission voltage measurement when using voltage method, artificially prepare stable line impedance. Generally provide 50Ω network impedance at RF section.
2. LISN isolates power grid and EUT. The DUT power supply must be pure. Otherwise, power grid will inject the interference into the DUT, EUT will also feed the interference into the power grid, and it will be unclear in the EMC analyzer which is the interference from EUT. Therefore, the test result is valid only isolate the both.
3. Make the interference signal from DUT couple into the EMC analyzer by the high pass filter of LISN, and prevent the power grid voltage to the EMC analyzer.
In the specific EMC test standard, a particular type of LISN is required, for EUT operation’s evaluation and characterization. Different types of LISN can be used for DC analysis, connection between single-phase or three-phase AC power source. The parameters to select LISN are impedance, insertion loss, rated voltage, rated current, the type number of the power supply wire and connector. In the conduction radiation measurement, the upper limit frequency of LISN is also very important; it is used to predict the radiation problem.
Lisun’s KH3962 EMI Receiver System combines with LISN to do EMI test. KH3962 is produced by the full closure structure and strong electro-conductibility material, which has high shielding effect. Due to this new technology for the EMI Test System, it solved the instrument self-EMI problem. The test results are according to the international format test report. The EMI Test System KH3962 fully meets CISPRI6-1, FCC, EN55015 and EN55022.
Lisun’s KH3962 EMI Receiver System is widely applied to Luminaries manufacturing enterprise and lab, such as Sharp Electronics in Memphis TN (USA), Institute for Optical Sciences (