Analysis of a PLL System as Analog Processor in CW Doppler Flowmeters

In this paper a phase-locked loop (PLL) system is analyzed in order to evaluate its performance for estimating the average frequency of an input spectrum made up by Ndiscrete components allocated in a frequency interval B. The system was studied first in the simplified case that the phase comparator has a linear characteristic. Next, a computer-aided simulation of the PLL system was performed taking into account the nonlinear characteristic of the phase comparator, assuming that the input spectral components have mutual random phase in (-¿, + ¿) interval and amplitudes with a distribution either uniform or obtained from a particular parabolic velocity profiles.