A 28-GHz Transformer-Based Oscillator With Implicit Third-Harmonic Extraction in 65nm CMOS

This paper presents a transformer-based oscillator with implicit third-harmonic extraction. The design incorporates a triple-coupled transformer to enable both second- and third-harmonic resonances, achieving effective harmonic shaping. The implicit harmonic extraction technique effectively enhances phase noise performance in the millimeter-wave frequency range while maintaining a wide frequency tuning range. Implemented in a 65-nm CMOS process, the proposed oscillator operates from 23.3 to 28.6 GHz, achieving a phase noise of -124.7 dBc/Hz at a 10-MHz offset from a 28.6 GHz carrier. With a power consumption of 5.6 mW, it attains a peak FoM of 186.3 dBc/Hz and a peak FoMT of 192.5 dBc/Hz.