A 1-V, 19.2-mW, 308-GHz Push-Push Balanced Colpitts Oscillator in 70-nm GaAs pHEMT Technology

This paper presents a submillimeter-wave (submm-wave) / terahertz (THz) push-push Colpitts oscillator that supports very low-voltage operation in 70-nm GaAs pHEMT technology. The oscillator core employs a common-drain (CD) balanced Colpitts topology with loaded shunt LC resonators at the drain, thereby constructively enhancing the second-harmonic (2f₀) output while suppressing unwanted harmonics. At an oscillation frequency (fosc) of 308 GHz, the push-push VCO demonstrates a phase noise (PN) of -96.8 dBc/Hz (10-MHz offset) and an output power (Pout) of -18.3 dBm, while consuming only 19.2mW from a 1-V supply. With the supply increased to 1.6V, the VCO operates at 311 GHz, achieving a PN of -97.7 dBc/Hz (10-MHz offset) and a Pout of -17.5 dBm. The VCO occupies a compact chip area of 370 µm × 445 µm (0.17mm²). To the best of the authors’ knowledge, this is the first GaAs oscillator operating above 300 GHz at such a low supply voltage, demonstrating state-of-the-art fosc and FoMT among previously reported GaAs and GaN HEMT-based harmonic oscillators, while remaining competitive with more advanced InP-based counterparts.