Abstract: A novel planar ultra-wideband antenna with dual band-notched characteristics is proposed.With the trapeziform structure at the bottom of radiating patch,good impedance match can be achieved.Meanwhile,two U-shaped slots are embeded into the radiating patch,to obtain the notched bands at the frequency of 3.5GHz and 5.5GHz.With and without the notched structure,the change of the current density on the surface of antenna is compared,and the cause of notched band is analyzed with the transmission line theory.The...