On the selection of passive elements for low phase noise LC tank VCO in 65 nm process

This paper describes the LC tank design for low phase noise LC VCO on the selection of passive elements. LC tank based VCO is commonly used for the low phase noise performance in most RF applications. Since quality factor of the LC tank is mainly dominated by the quality factor of the passive elements (inductor & capacitor) selection, this work presents the passive elements optimization based on the inductor and varactor optimization. Simulated in 65 nm process, higher Q is obtained for large width and minimum number of turns for the inductor and for the varactor design; the PMOS varactor operating in the depletion and accumulation regions allows large tuning range and less parasitic resistance.