Method and apparatus to tune and calibrate an on-chip oscillator in a wireless transceiver chip

A local oscillator, 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 fixed-capacitor input;
• a bank of fixed-value capacitors connected to said fixed-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 minimum and maximum output VCO-control signal magnitudes that match those of said first analog output;
• a frequency measurement device providing for a frequency reading 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 local oscillator, 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 fixed-capacitor input;
• a bank of fixed-value capacitors connected to said fixed-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 reading 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 local oscillator that depends on a voltage controlled oscillator with a selectable bank of fixed-value range capacitors, the method comprising the steps of:

• predetermining 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 a new operating frequency based on said minimum and maximum output frequencies in said list.

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

• means for predetermining 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;
• and
• means for responding to a request to move a new operating frequency based on said minimum and maximum output frequencies in said list.