Why does S12 decrease after adding an inductor to the port-to-ground branch?

[really12138]

My circuit is shown in the figure above, and I short-circuited two inductors to ground. The simulation diagram below shows the difference in S21 between the circuit without short circuit (S43) and the circuit with short circuit inductors (S65). Why is the dBS21 reduced at high frequencies? As I understand it, the inductor increases the impedance of the branch to ground, and the energy/signal should flow more to the middle branch, but the dBS21 shown in the simulation is reduced? What is the possible reason?

 

[Heaviside_Fan]

You are introducing LC resonances when you turn on the inductor. If you expand the frequency range, you will see the notches. At resonance the branch will create a short ckt to GND.

 

[dick_freebird]

Inductors (real ones) have a shunt C just like capacitors have shunt L. Go high enough in freq and you may see that "turn up", presuming it's modeled.

Anything you hang on the circuit pays some kind of tax.