cross couple VCO(why the voltage of tail current is f0 but no 2f0 )

[happsky]

1. I simulate a simple cross couple vco at 42GHz,but the drain voltage of the tail current MOS is have a period as the couple pairs f0,why?
2. why the phase noise is higher than 0?
The problem can be seen in the picture,thanks~

 

[happsky]

I know why it is f0 now,because my schematic is no symmetry.
and now the 2nd problem is puzzle me,and why the PN is a line but no (1/w)^3 and (1/w)^2 corners??