A 13.5-to-28.8GHz 72.3%-Locking Range Multi-Phase Injection-Locked Frequency Tripler with Improved Output Power and Wideband Subharmonic-Spur Rejection in 28nm CMOS

Injection-locked frequency tripler (ILFT) exhibits the potential to improve the PN and power efficiency of mm-wave LO generation, tripling down the operating frequency of the PLL and VCO. Yet, the conventional ILFT only can secure a superior PN performance over a narrow locking range. Recent efforts have been made to pursue locking-range extension for the ILFT to cover a wider spectrum, especially at the mm-wave. For example, adopting a low- Q resonant tank widens the locking range, but at the cost of higher power consumption and lower output power [1]. An alternative is to use injection-current boosting (ICB) technique plus a $6^{\text {th}}$-order resonator [2], but it penalizes the output signal power. Finally, the subharmonic spurs caused by the harmonic-rich injection signal remain severe [1] [2], and the subharmonic-spur rejection provided by the cascade power-hungry buffer is limited and highly frequency dependent.