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. © 2013 IEEE.