Low-Power Low-Phase-Noise Differentially Tuned Quadrature VCO Design in Standard CMOS

This paper describes the design and optimization of voltage controlled oscillators with quadrature outputs. Systematic design of fully integrated LC-VCOs with a high inductance tank leads to a cross-coupled double core LC-VCO as the optimal solution in terms of power consumption. Futhermore, a novel fully differential frequency tuning concept is introduced to ease high integration. The concepts are verified with a 0.25m standard CMOS fully integrated quadrature voltage-controlled oscillator (VCO) for zeroor low-IF DCS1800, DECT, or GSM receivers. At 2.5-V power supply voltage and a total power dissipation of 20 mW, the quadrature VCO features a worst-case phase noise of 143 dBc/Hz at 3-MHz frequency offset over the tuning range. The oscillator is tuned from 1.71 to 1.99 GHz through a differential nMOS/pMOS varactor input.