How to explain such a LC output wave?

[trashbox]

Hi

The attached schematic is a simple LC tank. Vs is a sine-wave(freq=2GHz,peak-to-peak value=0.4v) and Lg=3nH. I probe the signal at Port2.

In the attached simulation results,the yellow curve is Cp=2p(i.e.,the LgCp's resonance frequency is close to input signal's freq. 2G), the red curve is Cp=2.5p(i.e.,the LgCp's resonance frequency is far to input signal's freq. 2G).

Why does the input sigal seem to be modulated?
Or is there any problem in my simulation?

Thanks.

 

[Borber]

Problem is your simulation. Time step is too large. Try 50ps or less.