Patent ID: 7863993

Claim:
An apparatus including an oscillator for providing an oscillation signal with a controllable frequency, comprising: resonant circuitry having an impedance with resistive and reactive components; amplifier circuitry coupled to said resonant circuitry, including controllable reactive feedback circuitry providing controllable feedback reactance for said amplifier circuitry, and having an impedance with resistive and reactive components, wherein said controllable reactive feedback circuitry includes first and second serially coupled controllable capacitances having a first value C 1 and a second value C 2 , respectively, that are controllable in response to one or more capacitance control signals; and capacitance control circuitry coupled to said controllable reactive feedback circuitry to provide said one or more capacitance control signals with a plurality of values, wherein in accordance with a change between first and second ones of said plurality of control signal values, said first capacitance value C 1 changes from a first initial value C 1 a to a first subsequent value C 1 b for a first value change of C 1 b -C 1 a, said second capacitance value C 2 changes from a second initial value C 2 a to a second subsequent value C 2 b for a second value change of C 2 b -C 2 a, a ratio (C 2 b -C 2 a )/(C 1 b -C 1 a ) of said first and second capacitance value changes is approximately equal to a negative ratio (âˆ’C 2 )/(C 1 ) of said first and second capacitance values, and said resistive component of said amplifier circuitry impedance remains substantially equal in magnitude to said resistive component of said resonant circuitry impedance.