14.8 A 247-to-263.5GHz VCO with 2.6mW peak output power and 1.14% DC-to-RF efficiency in 65nm Bulk CMOS

Abstract

Signal generation at mm-Wave-to-THz frequencies is attractive because of its applications in bio-sensing, spectroscopy, detection of concealed weapons, as well as high-data-rate communication. CMOS is considered a potential platform to implement a low-cost and high-yield signal generation solution at this frequency range. Despite continuous scaling, effective fmax of active devices is not high enough and hence either harmonic oscillators or frequency multipliers are employed for high-frequency signal generation. In recent CMOS VCO designs, reasonable power levels (~1mW) and tuning range (~10GHz) have been reported at around 300GHz but with very low DC-to-RF efficiency (<;0.4%), which is undesirable for portable applications [1,4]. Moreover, power-level fluctuation is more than 3dB across the frequency range [1]. In this work, we introduce a scalable VCO architecture that efficiently generates and extracts the 2nd harmonic at 256GHz and hence simultaneously achieves high tuning range (16GHz), high output power (2.6mW), high DC-RF efficiency (1.14%), and low phase noise (-94dBc/Hz to -85dBc/Hz at 1MHz offset frequency across the tuning range). When compared to published state-of-the-art, this work demonstrates the highest output power, tuning range, and DC-to-RF efficiency, and the lowest phase noise among all CMOS VCOs above 200GHz.