Junior Member level 3
I am measuring S21 and S11 of a coaxial cable using VNA. I expected to see a S21 that decreases by frequency but has some ripply behavior. It means that in some regions S21 is improving by increasing the frequency. Does anyone know the reason for this behavior? At first, I thought it should be related to non-ideal input impedance but marker number 5 in the figure below rejects this idea.