Reflectarray Antenna design in HFSS

Hello everyone

I am trying to implement below paper in HFSS, it is a reflectarray implementation using HFSS
http://ieeexplore.ieee.org/stamp/sta...number=5276830
A Novel Microstrip Rectangular-Patch/RingCombination Reflectarray Element and Its Application Qin-Yi Li, Yong-Chang Jiao, and Gang Zhao

I have made a unit cell for the design using a floquet port and two master-slave boundary conditions and simulated in HFSS, the problem is the aforementioned paper has a linear linearly decreasing phase response upon increasing the patch element length. But mine simulation shows different response. Please see below

Also i have placed my HFFS design file at this google drive location, https://drive.google.com/file/d/0B2q...ew?usp=sharing
can anyone help me what am I doing wrong?

PS: I posted initially in HFSS group but then found this to RF forum so posted here as well