A 0.54 THz Signal Generator in 40 nm Bulk CMOS With 22 GHz Tuning Range and Integrated Planar Antenna

This work presents the design and measurements of a 0.54 THz signal generator implemented in a 40 nm bulk CMOS technology. An LC-VCO operating at 180 GHz is connected to a nonlinear buffer, which is designed to generate the wanted third harmonic at 540 GHz. The third harmonic is coupled via a transformer to the output. The developed techniques are implemented on two different chips: one with a probe pad for on-wafer measurements and one with an on-chip planar dipole. The measured peak output power using a WR-1.5 probe is -31 dBm at 543 GHz, for 16.8 mW of dc power consumption. By changing value of the parasitic I-MOS varactors of the LC-VCO (“parasitic tuning”), the output frequency can be tuned from 561.5 to 539.6 GHz, resulting in a 21.9 GHz tuning range, which is the highest reported so far for CMOS THz oscillators. The 3-dB output bandwidth is 5.5 GHz. The 540 GHz signal generator with on-chip antenna is used for THz imaging without the use of substrate or focusing lenses, demonstrating some of the capabilities of CMOS for low-cost, mass-produced THz imagers.