Page 6 - Phase-Locked Loops Design, Simulation, and Applications
P. 6
superimposed on its input signal. Let us suppose that the input signal of the PLL is buried in
noise. The PD tries to measure the phase error between input and output signals. The noise at
the input causes the zero crossings of the input signal u (t) to be advanced or delayed in a
1
stochastic manner. This causes the PD output signal u (t) to jitter around an average value. If
d
the corner frequency of the loop filter is low enough, almost no noise will be noticeable in the
signal u (t), and the VCO will operate in such a way that the phase of the signal
f
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