94 GHz CMOS down-conversion micromixer

A W-band (75~110 GHz) down-conversion mixer for 94 GHz image radar sensors in 90 nm CMOS is reported. Micromixer-based gain-enhanced technique, i.e. inductive series-peaking gain-enhanced single-in differential-out (SIDO) class-AB RF GM stage, is used to increase the output impedance and suppress the feedback capacitance C_gd of RF GM stage. Hence, conversion gain (CG), noise figure (NF) and LO-RF isolation of the mixer can be enhanced. The mixer consumes 7.2 mW and achieves excellent RF-port input reflection coefficient of -10~ -14.4 dB for frequencies of 81.4~110 GHz. The corresponding -10 dB input matching bandwidth is greater than 28.6 GHz. In addition, for frequencies of 90~96 GHz, the mixer achieves CG of 10.5~12 dB (the corresponding 3-dB CG bandwidth is 22 GHz) and LO-RF isolation of 40.2~46.2 dB, one of the best CG and LO-RF isolation results ever reported for a down-conversion mixer with operation frequency around 94 GHz. Furthermore, the mixer achieves an input third-order intercept point (IIP3) of 1 dBm at 94 GHz. These results demonstrate the proposed down-conversion mixer architecture is very promising for 94 GHz image radar sensors.