The first 50-GHz to 110-GHz downconverter in 45-nm digital CMOS is presented along with the mm-wave characterization of AMOS varactors, inductors and transformers. The varactor Q is higher than 6, up to 94 GHz. The downconverter gain is 15 dB at 111GHz, and is employed as a broadband test vehicle to characterize the optimal noise figure current density (JOPT) of 45-nm MOSFETs in the 50 GHz to 110 GHz range.