Need help for ADS error message

Hi all,

I have this problem every time I increase the value of RF chokes (L4 and L5) above 5nH. The simulation gave an error message:

" Internal timestep 5.90440e-24 too small at time 4.00940e-10. "

How could I solve this problem? I'm designing current mode class-D RF amp with HEMT as used transistor(see attachment).

Thank you

Such error messages are-generally-result of convergence problems which come from frequently semiconductor models,floating nodes,extreme component values,interlacing meshes etc.
In your case, using multiplier is not really lovely for transient simulator because this component is behavioural one and math. expressions in it can create some convergence problems.
You should do this multiplication in the source by defining a PWM function in "User defined voltage source"
This may be one of the reasons, there are-perhaps- other reasons,check them out..