A Very Low Phase-Noise Transformer-Coupled Oscillator and PLL for 5G Communications in 0.12 $\mu$ m SiGe BiCMOS

This article presents a 9.9-12.45 GHz voltage-controlled oscillator (VCO) designed in 0.12 μm SiGe BiCMOS with a focus on achieving the lowest possible phase noise using only a single core and maintaining the recommended Vdd of the technology. The oscillator consists of a cross-coupled design utilizing a transformer-coupled resonant tank, which takes advantage of tank parasitics to create harmonic resonances. An analysis is offered, which justifies the use of the transformer tank, noting its importance in mitigating the practical limits imposed during layout on equivalent LC tanks. An excellent phase noise of -122 dBc/Hz is measured at 1 MHz offset from the carrier resulting in a figure of merit (FoM) and tuning FoM (FoMT) of -183 and -190 dBc/Hz, respectively. The VCO is incorporated into a type-II charge-pump-based phase-locked loop (PLL) with intent to be used as the local oscillator (LO) generation in a potential fifth-generation (5G) communication system.