A 5 to 11.1 GHz Quad-Core Quad-Mode Octave Tuning-Range CMOS LC VCO

This paper presents an octave tuning-range LC VCO which can be used in the phase-locked loop to synthesis all frequencies up to the highest oscillation frequency. The proposed VCO employs the E-M mixed-coupling technique which compromises four LC tanks coupled either through magnetic or electric coupling, thereby generating four distinct resonances. Switched tail resistors are added to suppress FoM variation over the tuning range. To further enhance the phase noise performance, customized transistor designs are utilized instead of the PDK provided alternatives for a more compact layout to minimize wiring length from tank to active core. The proposed VCO, fabricated in 65nm CMOS process, demonstrates a 75.7% tuning range from 5 GHz to 11.1 GHz with an optimal -145.8 dBc/Hz phase noise at 10-MHz offset, corresponding to a figure-of-merit-tuning (FoM
T
) of 205 dBc/Hz. Notably, the FoM
T
variation remains considerably small, at less than 2.5dB, over the entire tuning range.