#312 Ngspice-42 or 43 Cannot calculate minimum noise figure (NFmin) if S2P file is used Issue created by Atif07Ali Environment Ngspice 42 or 43 Qucs-s 24.3 I am trying to design an LNA at 170 GHz frequency using SG13G2. I tried to build the circuit with transmission lines, using the S2P files of transmission lines. I faced the problem of 'nan' in the minimum noise figure (NFmin). It seems that the simulator cannot calculate NFmin. if I use lumped elements, the NFmin gives the right value. However, when I use S2P files as the transmission lines, the NFmin does not provide any value. It seems that the simulator cannot calculate noise figure when there are S2P files. Expected Behavior The behavior has been simulated using lumped elements only. image Actual Behavior This is the behavior after using S2P files. The NFmin gives "nan" value. image image Steps to Reproduce the Problem 1. Create the circuit like the schematic. 2. Provide any S2P file to the 2-port s-param. 3. Turn on the noise in "S parameter simulation" and simulate. plot nfmin. IHP-GmbH/IHP-Open-PDK