why RF signal is not sin wave?

Hi guys
I did a simulation on my circuit, one side(1) of RF ground is connected to ground and another side(2) is connectted to a transistor, after my simulation, I added a pin in side(2) and suppose the output should be sin wave since side(1) is connectted to ground. But my simulation results show it is not a sin wave, it has some DC term and some AC term, did anyone face same problem before and figure it out,
what's the reason for this? How to fix it?
Thanks a lot

Sometimes the simulation time is not long enough for a coupling capacitor to discharge.

If you don't have one, then the bias point of the transistor...

If you don't have a CC then your transistor should be biased by the dc value of your source. If it's zero, then your transistor is biased at 0 V.

Because it include so much noise, but after filter and LNA it will be a sine wave.

hello,

You can use the source of the Sparam simulation such as psin where you can change the type of the source (sine or dc) or other sources.


Good Work.