Phase modulation

Hi,

The sin(2*pi*fc*t) indicates the fundamental sinusoid component of the clock signal. This is a standard equation and the 2*pi allows the sine values to cycle around...

The picture explains a clean clock jitter on the basis of two sinusoid phase modulation. You can see there is a clear relationship between clock jitter and the amplitude of the modulating sinusoid.

In the digital domain you can reproduce that in a DDS circuit(Direct Digital Synthesiser) by generating the clock "sinusoid" component according to word value decided by a lut containing one cycle of the modulating sinusoid amplitude values).

edit: alternatively, use altera NCO and set to phase modulation then pass the phase modulation value as variable input from the LUT. (altera NCO is an implementation type of DDS)

Kaz