A 110-GHz Push-Push Balanced Colpitts Oscillator Using 0.15-µm GaN HEMT Technology

This paper presents a sub-THz oscillator using 0.15-µm GaN HEMT technology. A push-push balanced Colpitts topology is proposed to achieve a very high operating frequency while also with high output power under low DC power consumption. The source-floating transistor with an in-house built three-terminal transistor model was employed to allow using the transmission line (TL) at the source node for Colpitts feedback capacitor with improved negative resistance. In addition, the layout is in Grounded-CPW (GCPW) configuration with backside vias to achieve an optimized low-loss TL structure. The measured results show that the GaN oscillator can reach a peak output power of -2.1 dBm with a tuning range from 107.9~109.5 GHz, and the measured phase noise is -110.8 dBc/Hz at a 10 MHz offset.