This paper presents a low power and low noise sub-harmonically injection-locked PLL using a 20GHz sub-sampling PLL (SS-PLL) and a quadrature injection locked oscillator (QILO). Lower in-band phase noise and out-of-band phase noise have been achieved through the sub-sampling phase detection and sub-harmonic injection techniques, respectively. Implemented in a 65nm CMOS, this work can support all 60GHz channels and achieves a phase noise of -115dBc/Hz at 10MHz offset while consuming 20.2mW and 14mW from the 20GHz SS-PLL and the QILO, respectively.