Analysis and optimization of PLL´s with signal injection in synchronization systems

We consider the use of phase-locked loops with signal injection (PLLI) in clock synchronization applications. We show that the PLLI performs in fact an in-phase-quadrature demodulation. As a result the jitter performance of the PLLI depends on the power spectral densities (PSD) of the in-phase and quadrature components of the disturbance and on their cross-spectrum. If the components are correlated the PLLI can if suitably designed explore this correlation to reduce the jitter. We address the problem of optimum prefiltering for a maximum jitter reduction and numerical examples for two types of signaling are presented which show that considerable improvements can be achieved relatively to the conventional PLL