plz help me in designing a cascode low noise amplifier (LNA)

HI

i am using hspice to design a inductively degenerated cascode LNA

my problem is :




i did the cascode lna for 2.4GHz ,in the DC analysis it is showing a cgs of 452fF , based on this if i calculate Lg+Ls and used those inductor values, but on the graphs it is showing a dip in S11 curve at 1.9GHz instead of 2.4GHz, so to increase the dip frequency i increased Lg+Ls and the dip is occurring at 2.4GHz but now the corresponding cgs should be 940fF .

so my doubt is : is it showing an actual cgs of 940fF as 452fF? or is there any stray capacitance affecting?how to solve this?

thank you
deepak