How to setup the excitation?Hertzian Dipole excitation in HFSS

i use incident wave?Hertzian Dipole excitation to excite my object in HFSS ,but i dont know the parameter of the dipole ,such as the value of I*Dipole length
,the radius of the surrounding sphere ? besides my object is very small ,less than 100 nm.anyone who know it, plz help.

this may help
http://www.scribd.com/doc/16584538/HFSS-Tutorial

thank u, but that is not my problem , i need to use a excitation ( HFSS—excitation—assign—incident wave — Hertzian Dipole wave , ),then the parameter setup is my problem .