Sirf Technology, Inc.

Ray Herman

Sanjai Kohli

Neng-Tze Yang

Liping Zhang

A method and a voltage-controlled oscillator provide an output signal with a frequency within one of a plurality of frequency bands, while reducing or eliminating temperature-induced band-switching or other drifts in operating frequency. The band-switching is reduced or eliminated by providing a circuit that adjusts a tuning sensitivity according to a calibration performed under test conditions. For example, such a voltage-controlled oscillator may include (a) a digitally controlled variable current source for providing a first control current to select one of the frequency bands for the voltage-controlled oscillator; (b) a variable transconductance circuit providing a second control current to compensate a variation in operating frequency; and (c) a control circuit for varying the frequency of the output signal in accordance with the first and second control signals. The variable transconductance circuit may be programmable by selectively activating elements of an array of varactor circuits, according to a capacitance associated with each varactor circuit. The capacitance associated with each varactor circuit is binary weighted.

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Ray Herman