Control and calibration of external oscillators

A method of electronic oscillator control, the method comprising:

• tuning an oscillation frequency of a controllable oscillator using a first varactor, the controllable oscillator external to a semiconductor die;
• tuning the oscillation frequency of the controllable oscillator using a second varactor;
• controlling the first varactor to provide fine tuning to the controllable oscillator using a phase-locked loop (PLL) on the semiconductor die;
• and
• controlling the second varactor to provide coarse tuning to the controllable oscillator using a calibration circuit of the semiconductor die.

A radio frequency communication system comprising:

• a mixer controlled by an oscillator signal;
• and
• a local oscillator comprising:
• a semiconductor die,
• a controllable oscillator external to the semiconductor die and configured to output the oscillator signal,
• a first varactor configured to tune an oscillation frequency of the controllable oscillator, and
• a second varactor configured to tune the oscillation frequency of the controllable oscillator,
• wherein the semiconductor die comprises a phase-locked loop (PLL) configured to provide fine tuning to the controllable oscillator by controlling the first varactor, and a calibration circuit configured to provide coarse tuning to the controllable oscillator by controlling the second varactor.