Patent ID: 9608647
Date: 2017-03-28
CPC Classifications: H03B,H03L

Claim:
1. A method for calibrating a voltage-controlled oscillator (VCO) of a phase-locked loop (PLL) system, where a VCO output frequency is dependent on a fine-tuning control voltage input, a coarse-tuning control input and one or more operational conditions, where the VCO output frequency varies monotonically with changes in each of the one or more operational conditions, the method comprising: providing a frequency characteristics dataset indicating the VCO output frequency across a range of allowable values for each of the coarse-tuning control input and the fine-tuning control voltage input and a range of expected values of the one or more operational conditions; for each of a plurality of coarse-tuning control input settings, determining a polynomial function describing a calibration voltage for the control voltage input with respect to the one or more operational conditions, wherein the polynomial function is determined based on the frequency characteristics dataset to generate a constant VCO output frequency such that the constant VCO output frequency is a midpoint of a usable VCO frequency range, wherein the usable VCO frequency range comprises all VCO output frequencies that can be generated at the coarse-tuning control input setting over all of the range of expected values of the one or more operational conditions using only allowable values of the fine tuning control voltage; measuring the one or more operational conditions; placing the PLL system in an open-loop state; applying the calibration voltage corresponding to the measured one or more operational conditions as determined by the polynomial function to the control voltage input; sweeping through a range of coarse-tuning control input values to determine a selected coarse-tuning control input that minimizes a difference between the constant VCO output frequency and a target frequency; and enabling the coarse-tuning control input setting of VCO corresponding to the selected coarse-tuning control input.