Different result between sp & hpsp frequency response

Hi everybody, 

I have the follwing circuit to check its magnitude/phase frequency response (this circuit is non-linear and also generate other harmonics rather than fundamental one) 

when i simulated with hpsp to check whether how it works with large input signal , the results are quite different in S-parameter 

i dont know how to explain it, even set input power of hpsp to about -80 dBm (small enough) : 

could anyone give me some explainations ?

this is my sp & hpsp/hp settting: 

Thanks,       

Binh