Patent ID: 8183949

Claim:
A method of operating a phase locked loop (“PLL”) including a voltage controlled oscillator (“VCO”), comprising: a) switching the VCO to an operating band selected from among the plurality of operating bands of the VCO; b) causing the VCO to oscillate at a minimum output frequency for the selected operating band by supplying a control voltage at a minimum level thereto and counting pulses in feedback from the minimum output frequency during a first time interval; c) causing the VCO to oscillate at a maximum output frequency for the selected operating band by supplying a control voltage at a maximum level thereto and counting pulses in feedback from the maximum output frequency during a second time interval; d) determining a true center frequency of the selected operating band from the count of the pulses during the first and second time intervals; e) allowing the PLL to lock the output frequency at a lock frequency when the lock frequency is within the selected operating band and measuring the lock frequency by counting pulses in feedback from the lock frequency; f) storing a current difference value determined as a difference between the true center frequency of the selected operating band and the measured lock frequency; and g) switching the VCO to another operating band selected from among the plurality of operating bands; and h) repeating steps (b) through (g) so long as the current difference value obtained when the VCO is set to the selected operating band is smaller than the lowest previously obtained difference value obtained when the VCO was previously set to another operating band, so as to select the operating band for which the measured lock frequency is closest to the true center of the frequency range of the selected operating band, such that the method is capable of setting the VCO to the operating band for which the measured lock frequency is closest to the true center of the frequency range of any of the operating bands, even if the output frequency of the VCO is a nonlinear function of the control voltage.