There is provided a signal generator and associated method for generating a source signal. The signal generator includes a frequency generator for providing an oscillating signal, a phase comparator, a first phase modulator, a second phase modulator and a phase shifter. The phase comparator is adapted to compare a phase signal with a feedback signal and to generate an error signal to control the phase of the oscillating signal. The first and second phase modulators are adapted to provide a first phase control word and a second phase control word respectively. The phase shifter is adapted to modulate the oscillating signal based on the second phase control word to generate the source signal. The source signal comprises the feedback signal.