A noise tolerant voltage controlled oscillator is described. The voltage
controlled oscillator include a varactor element as part of an LC tank
circuit. The varactor element is biased by a bias signal and a
bias-dependent control signal. The bias-dependent control signal tunes
the LC tank circuit. Because the control signal is bias-dependent, noise
and other deleterious influences do not cause the varactor element to
deviate in capacitance. Instead, the bias-dependent control signal is a
tuning signal that is centered around the bias signal, which allows the
varactor element to provide a constant capacitance in the event of a
varying bias signal.