Silicon technology now offers a path to both capable and economical systems operating at 200 GHz and beyond. This option has arisen because of recent progress in complementary-metaloxide- semiconductor (CMOS) integrated circuits and silicon-germanium (SiGe) heterojunctionbipolar- transistor (HBT) technology. Underscoring this shift is the recent demonstration of the following: a 140-GHz fundamental-mode voltage-controlled oscillator (VCO) in 90-nm CMOS; a 410-GHz push-push VCO with an on-chip patch antenna in 45-nm CMOS; a 125-GHz Schottky-diode frequency doubler; a 50-GHz phase-locked loop (PLL) with a frequency- doubled output at 100 GHz; a 180-GHz Schottky-diode detector; and a 700-GHz plasma wave detector in 130-nm CMOS.

This work was performed by Texas Instruments' Eunyoung Seok and Swaminathan Sankaran, Dongha Shim and Ruonan Han from the University of Florida, Chuying Mao from Integrated Device Technology, MediaTek's Changhua Cao, Wojciech Knap from France's Universit Montepellier, and Kenneth K. O from the University of Texas. They concluded that it is feasible to use a mainstream foundry logic CMOS process to fabricate signal generators and detectors that operate at millimeter-wave and sub-millimeterwave frequencies. Before a practical system can be realized, however, technical challenges must be overcome. For example, CMOS circuits must be proven capable of supporting practical sub-millimeter- wave/terahertz systems. See "Progress and Challenges Towards Terahertz CMOS Integrated Circuits," IEEE Journal Of Solid-State Circuits, August 2010, p. 1554.