20.5 1.4THz, −13dBm-EIRP frequency multiplier chain using symmetric- and asymmetric-CV varactors in 65nm CMOS

THz region of electromagnetic spectrum has unique features making it attractive in spectroscopic studies, material inspection, tera-bit/sec communication, and biological- and non-biological-imaging applications. Owing to challenges in producing sufficiently strong signals, this region of spectrum has been exclusively served by III-V electronics or bulky cryogenic-temperature technologies such as QCLs [1]. Recently, advanced half-THz SiGe technologies and multi-element spatial power-combining techniques to increase the output power were successfully used to generate 0dBm of power at 0.53THz and -17dBm peak EIRP at 0.82THz [2-4]. Both solutions, however, suffer from low realized bandwidths (3%), limiting their utility in a slew of imaging and communication applications. Alternatively, high-quality accumulation-mode symmetric MOS varactors (SVARs) [5] in standard CMOS have been demonstrated as efficient odd-harmonic generators in broadband tripler and quintupler operating around 0.4THz [6] and 0.7THz [7], respectively. In this work, a 1.4THz multiplier chain of 10th order using MOS VARs in a 65nm standard CMOS process is demonstrated. The multiplier incorporates a new asymmetric VAR (ASVAR) for multiplication by 2 in addition to an SVAR for frequency quintupling. The circuit produces -13dBm peak EIRP at 1.33THz and operates over a setup-limited bandwidth of more than 11%. The fully integrated multiplier chain does not require any silicon lens or substrate thinning making it a compact and affordable solution for emerging THz applications.