Phase-locked loop (Lur'e system) Z-domain analysis

Hi,

Anyone know about how to transform the PLL configuration into the Lur'e system[IMG]http://www.engineersedge.com/engineering-forum/attachment.php?attachmentid=1303&stc=1[/IMG], and then find the corresponding G(z) linear system? Besides,from there how do I find the state-space matrices A,B,C and D which are in terms of the filter's parameters (Af,Bf,Cf,Df) and the VCO's parameters (Av,Bv,Cv,Dv). G(z) linear system includes filter and VCO.

Thanks.