A clock signal generator includes a phase-lock loop for generating an imaging clock signal having a frequency based on a reference clock signal. The imaging clock signal generator also includes a modulation circuit for determining a number of pixels in a horizontal line of an image to be generated based on the imaging clock signal. The modulation circuit generates a modulation signal based on the determined number of pixels and the clock signal generator spreads the frequency of the imaging clock signal across a frequency range based on the modulation signal. In this way, the clock signal generator reduces electromagnetic interference in the imaging clock signal. In further embodiments, the clock signal generator generates an adjustment signal for adjusting the frequency range based on the frequency of the reference clock signal and the frequency of the imaging clock signal.