A novel and useful digitally controlled injection-locked RF oscillator with an auxiliary loop. The oscillator is injection locked to a time delayed version of its own resonating voltage (or its second harmonic) and its frequency is modulated by manipulating the phase and amplitude of injected current. The oscillator achieves a narrow modulation tuning range and fine step size of an LC tank based digitally controlled oscillator (DCO). The DCO first gets tuned to its center frequency by means of a conventional switched capacitor array. Frequency modulation is then achieved via a novel method of digitally controlling the phase and amplitude of injected current into the LC tank generated from its own resonating voltage. A very linear deviation from the center frequency is achieved with a much lower gain resulting in a very fine resolution DCO step size and high linearity without needing to resort to oversampled noise shaped dithering.