A 94 GHz down-conversion mixer in 90 CMOS process is reported. The mixer has a double-balanced Gilbert cell with an NMOS LC-oscillator-based RF transconductance (GM) stage load for noise figure (NF) suppression and conversion gain (CG) enhancement. The mixer consumes 9.5 mW and achieves excellent RF-port input reflection coefficient of -27.2 dB at 94 GHz, LO-port input reflection coefficient of -15.1 dB at 93.9 GHz, and IF-port input reflection coefficient of -10.3 dB at 0.1 GHz. In addition, the mixer achieves CG of 4.9~7.9 dB, NF of 15.4~21.2 dB and LO-RF isolation of 38.5~44.7 dB for frequencies of 75~100 GHz, one of the best CG, NF and LO-RF isolation results ever reported for a down-conversion mixer with operation frequency around 75~100 GHz. Furthermore, the mixer achieves an excellent input third-order intercept point (IIP3) of 2.6 dBm. These results demonstrate the proposed down-conversion mixer is promising for 94 GHz image radar sensors.