This tutorial will help you to plot the dispersion diagram using HFSS

http://www.emtalk.com/forums/viewforum.php?f=5&sid=661684c1df9c1e69628bb7cbcd255db6

this links will be helpful for you

http://www.edaboard.com/thread123197.html

http://search.edaboard.com/dispersion-diagram-cst.html

In my early days, I used The S21 (Phase) curve, and used the "unwrap" plotting function to just unwrap the phase curve and plot it vs the radian curve.

If you coldn't follow the HFSS or CST plotting tool, i think this is the easiest way to do it.

thank you dears. all of your answers are good and helpful. i try them.

Please go throught this pdf, it will helpfull to get dispersion curv using cst.

thank you dear Wasim Akaram. i study this pdf and finally i cant understand that. but i try again. 

hi azita gudarzi...plz try to follow step by step procedure given in that pdf then i think u will get through...

all the best