how to design perfect mixer

hi i m designing RF mixer for 10db using formulas but when i m simulate it in cadence gain is very low and other than for which i designed it is coming around -10db

So what is your question? I doubt if there is a perfect mixer, each design is optimised for some parameter or other, even if its the cost of it.
Frank

no ,perfect means i m designing mixer for certain gain but when i m simulating it gain is very far away from value which i consider during design

A circuit and the LO injection level would be useful.
Frank