phase noise of pll

Phase Noise
The Phase noise in a synthesizer is, most likely, the most difficult problem to resolve.
The noise appears in the system due to a noise of 1/f and thermal noise in the devices that it is
generated particularly by the VCO.
The noise injected into the oscillator by its devices or by external means, can influence
both the phase as well as the amplitude of the output signal, although in most cases the effect
of the distortion in the amplitude is negligible. The phase noise can be seen as a random
variation of the zero crossings from its ideal position throughout the time axis. The
designation phase noise is used in the frequency domain, whereas in the time domain, we use
the designation jitter