Phase noise and transconductance improvement in monolithic differential LC-VCOs

A novel solution to the improvement of phase noise and negative transconductance in differential LC-voltage-controlled oscillators (VCOs) is proposed. Feedback injection currents improve the loading effect of the switch transistor moving towards triode region and improve the total transconductance and differential output phase noise at no extra power consumption cost. A property of self-locking between the zero crossings of the output voltage and currents that may invoke further research studies is introduced. The application of the proposed solution to the design of complementary metal-oxide semiconductor (CMOS)-based GHz range low phase noise and/or low-power monolithic differential LC-VCOs is discussed. Post-layout results and Advanced Design System simulations using CMOS 0.18 µm TSMC RF design kit are used for evaluation and comparison, respectively.