A linearized voltage-controlled oscillator for dual-path phase-locked loops

A voltage-controlled oscillator linearization technique suitable for dual-path phase-locked loops is presented. In the proposed scheme, the state of the integral control path sets the gain of a transconductor in the proportional path in such way that nearly constant VCO gain through the proportional path is achieved. A detailed analysis and design example is presented in the context of delay-interpolating ring-based VCOs. Simulation and measurements in ST 90 nm CMOS technology show that the proposed technique is effective in reducing gain variations across the VCO´s tuning range from an uncompensated spread of 1:4 to an average of 1:1.3.