Terahertz RF Front-End Employing Even-Order Subharmonic MOS Symmetric Varactor Mixers in 65-NM CMOS for Hydration Measurements at 560 GHz

A 560-GHz RF front-end employing MOS symmetric varactor (SVAR) subharmonic mixers achieves a minimum SSB noise figure (NF) of 35 dB in the 4th order subharmonic mixing (SHM) mode which is 5–7 dB lower than that of SiGe HBT mixers. The front-end fabricated in 65-nm CMOS also achieves 45-dB SSB NF for 6th order SHM at RF=810 GHz and 60-dB SSB NF for 10th order SHM at RF=1.2 THz. Use of SVAR's in a mixer is the first and the 1.2-THz RF is the highest among the silicon coherent RF front-ends.