Utilizing the circuit simulator SPICE, we designed a 1.9GHz CMOS up-conversion mixer and explained in detail the simulation procedures including device modeling for the circuit design. Since the measured characteristics of the chip fabricated using the $0.5{mu}m$ standard CMOS process had shown a big deviation from the characteristics expected by the original simulations, we tried to figure out the proper reasons for the discrepancies. Simulations considering the discovered problems in the original simulations have shown the validity of the simulation method tried for the design. We have shown that the utilized standard CMOS process can be used for the implementation of the chip characteristics similar to those of the equivalent chip fabricated using the GaAs MESFET process.