An impulse generation circuit for a voltage controlled oscillator includes a zero-crossing detector configured to detect a zero-crossing time of an output signal of the voltage controlled oscillator. The zero-crossing time corresponds to a time that the output signal crosses from a first polarity to a second polarity. A delay circuit is configured to wait for a delay period based on the zero-crossing time and a voltage peak of the output signal. An impulse generation module is configured to generate an impulse subsequent to the delay period. An energy injector is configured to, in response to the impulse, connect a supply voltage to the output signal of the voltage controlled oscillator for a duration of the impulse.