A Multi-Phase coupled oscillator using dual-tank magnetic coupling technique

This paper presents a novel coupled-oscillator RFIC for multi-phase clock generation. The design achieves low phase noise while maintaining strong coupling among oscillator cores. The proposed transformer-based dual-tank topology forms a loop of coupling path for enhanced multi-phase coupling. The phase noise optimization is accomplished by leveraging the dual-tank and the adaptive-biasing feedback techniques, while the transformers facilitate strong magnetic coupling among oscillator cores. Full electro-magnetic (EM) modeling of all transformers and the passive interconnecting routes has been performed using EMX in order to ensure that simulated performance reflects measurement environment. The prototype of the proposed circuit with 8 phases is implemented in a 65nm CMOS RF SOI technology. The measured phase noise is -124.3 dBc/Hz @ 1MHz offset from 2.41 GHz with 7mw power consumption for each core, and the operating frequency can be digitally tuned from 1.81 GHz to 2.41 GHz.