Frequency synthesizer using a VCO having a controllable operating point, and calibration and tuning thereof

A frequency synthesizer, comprising:

• a voltage-controlled oscillator (VCO) providing a variable frequency output that depends, in part on an analog control input signal, and in part on a capacitance connected to a capacitor input;
• a switchable bank of capacitors having a switch input, and connected to said capacitor input, the switchable capacitor bank providing a selectable range of operating frequencies for the VCO;
• a main charge pump connected to control the VCO and having a first analog output control signal that can span between a minimum and a maximum output magnitude which are dependent on operating conditions and electronic construction;
• a replica charge pump having an electronic construction and operating conditions that duplicate the main charge pump such that it provides a second analog output with minimum and maximum output VCO-control signal magnitudes that match those of said first analog output;
• a frequency measurement device providing for a frequency rending of a frequency output of the VCO for each of said selectable range of operating frequencies produced by individual ones of the bank of fixed-value capacitors;
• and
• a calibration table constructed of a plurality of said frequency measurements taken while said second analog output from the replica charge pump is driving the VCO at said minimum and maximum output VCO-control signal magnitudes.

A frequency synthesizer, comprising:

• a voltage-controlled oscillator (VCO) providing a variable frequency output that depends, in part on an analog control input signal, and in part on a capacitance connected to a capacitor input;
• a bank of capacitors connected to said capacitor input and providing a selectable range of operating frequencies for the VCO;
• a main charge pump connected to control the VCO and having a first analog output control signal that can span between a minimum and a maximum output magnitude which are dependent on operating conditions, and electronic construction;
• a replica charge pump having an electronic construction and operating conditions that duplicate the main charge pump such that it provides a second analog output with a predetermined output VCO-control signal magnitude that matches those of said first analog output;
• a frequency measurement device providing for a frequency rading of a frequency output of the VCO for each of said selectable range of operating frequencies produced by individual ones of the bank of fixed-value capacitors;
• and
• a calibration table constructed of a plurality of said frequency measurements taken while said second analog output from the replica charge pump is driving the VCO at said predetermined output VCO-control signal magnitude.

A method for operating a frequency synthesizer that depends on a voltage controlled oscillator with an operating frequency range that depends on the setting of a selectable bank of capacitors and on the magnitude of a control signal, the method comprising the steps of:

• predeterming what minimum and maximum output frequencies result from driving a control input of a voltage-controlled oscillator (VCO) at the minimum and maximum outputs obtainable from a main charge pump;
• tabulating a list of said minimum and maximum output frequencies obtained in the step of predetermining;
• and
• responding to a request to move to a new operating frequency range based on said minimum and maximum output frequencies in said list.

A means for operating a frequency synthesizer that depends on a voltage controlled oscillator with a selectable bank of fixed-value range capacitors, comprising:

• means for pertaining what minimum and maximum output frequencies result from driving a control input of a voltage-controlled oscillator (VCO) at the minimum and maximum outputs obtainable from a main charge pump;
• means for tabulating a list of said minimum and maximum output frequencies obtained in the step of predetermining;
• means for responding to a request to move a new operating frequency based on said minimum and maximum output frequencies in said list;
• means for providing the drive of said VCO from the output of a replica charge pump as an alternate to a main charge pump that drives said VCO, the replica pump constructed such that the electronics of said replica charge pump simulate that of said an charge pump;
• and
• means for operating said main charge pump and said replica charge pump under the same operating conditions to obtain at least matching minimum and matching maximum outputs that drive said VCO.