A Compact 275 GHz Harmonic VCO with-2.6 dBm Output Power in a 130 nm SiGe Process

This paper presents a new method for harmonic VCO design. A capacitive degeneration is employed to shape the output conductance (G(out)) of the cross coupled structure to increase the possible oscillation frequency in addition to output power. An inductive feedback is utilized to provide large voltage swing at the input of the transistors to boost harmonic generation. Finally, the passive components at the collector improves the delivery of generated harmonic current to the load in addition to setting the oscillation frequency. Using this method, a 275 GHz harmonic VCO is designed and implemented in a 130 nm SiGe process. The measurement results show -2.6 dBm peak output power, 1.1% dc-to-RF efficiency, 3.3 % tuning range (270.3 GHz to 279.3 GHz). The chip area excluding the pads is 0.022 mm(2) which results in 25 mW/mm(2) power per area and 50 %/mm(2) efficiency per area which is highest among reported SiGe/CMOS oscillators working above 0.75 f(max).