Ignat wrote ("AD9548 DPLL is not locked" http://ez.analog.com/thread/41342)
that the PLL has ensured the synchronization frequency, phase but remained decoherent. I think that phase PLL system should not be coherent, phase should slide and track the error frequency. To synchronize it is up to the phase need other devices. This is my humble opinion. Interestingly, thinks professional Mr. Paul Kern?