I am confused regarding the working of a Line Impedance Stabilizer Network. To analyze the conducted EMI of my DC-DC converter (simulation only at this point of time) I know we need to connect in series a LISN device. The filter portion will come after the LISN module, before the converter. My question is, isn't the LISN itself acting like a filter? Because when I was simulating the converter I had first chosen the LISN inductor = 50 uH, and this caused trouble since it is a 12 V to 5 V buck converter. When I changed it to 5 or 10 uH, all the waveforms were as expected.
Also, how is the correct LISN chosen in the real world for a switching converter?