Investigation and Comparison of Phase noise and FoM of LC VCO and QVCO of 60 GHz to that of a Distributed Oscillator of 30 GHz with a Doubler

An LC VCO is designed for 60 GHz while the distributed oscillator (DO) is designed for 30 GHz, in 65 nm RF CMOS, both having a high output power of around 10 dBm (10 mW). The performance of two oscillators topologies, LC VCO and distributed oscillator, is compared. Simulation results show that the 30 GHz distributed oscillator has better phase noise compared to that of 60 GHz LC oscillator. The phase noise of DO is -101.85 dBc/Hz at 1 MHz offset from 30 GHz carrier while that of LC oscillator, it is -88.88 dBc/Hz at 1 MHz offset from 60 GHz carrier. A doubler is then used to double the DO frequency to 60 GHz but phase noise remains the same. Thus the 30 GHz distributed oscillator or even an LC VCO at 30 GHz, with a doubler can be used to achieve better phase noise performance at a higher frequency of 60 GHz. The 30 GHz LC VCO of phase noise -99.85 dBc/Hz at the same time has lesser DC power consumption than 60 GHz LC VCO. The 30 GHz DO and LC VCO has better FoM due to better phase noise performance, as compared to 60 GHz LC VCO. A 60 GHz LC QVCO has also been implemented having better phase noise than 60 GHz LC VCO. The QVCO provides 90° quadrature phase signals at its output. This work compares for the first time the performance of a distributed oscillator with that of an LC VCO and QVCO.