how to start about designing phase locked loops

i want to start designing practical pll. can anyone help me out.
i have studied a lot about pll theory.
Is there any simulation tool available where i can design and simulate pll.

LTspice... I used it to simulate PLL too.

Added:
In real time and as Laplace blocks (function of theta, phase)

Analog device , ADISimPLL is a good choice.