hi
if u want to plot this type of graph u should catch data from impedance vs change in frequency.orcad software doing such work.u should define a parameter for your element and then sample impedance vs change in frequency step.
But i want to do it in HFSS (11) only, i don't wanna to download/buy any other software for that.
there must be some way for that.so if somebody can let me know than it will be great help to me
If you want to plot the PORT IMPEDANCE versus FREQUENCY, then you can plot "Port Zo" versus frequency ( it is available in one of the options) if you have created waveports for the ports and the port impedance is "not renormalized". If you renormalized your port impedance then you will see a straight line at 50 ohms for all the frequencies.