An inductorless injection-locked PLL with 1/2- and 1/4-integral subharmonic locking in 90 nm CMOS

An inductorless PLL with 1/2- and 1/4-integral as well as integral subharmonic injection locking is realized, which can solve tradeoff between the selectable frequency step and phase noise of injection-locked PLLs (ILPLLs). The proposed ILPLL was fabricated in 90 nm CMOS process (PLL area: 0.083 mm², tuning range: 1.1-2.0 GHz). For a 80 MHz reference, it shows that the 1-MHz-offset phase noise is -106 dBc/Hz at 1.8 GHz (= 11.25 × 160 MHz) with injection. A 15-dB reduction is achieved, compared with that in the case without injection.