A planar UWB Antenna with band rejection characteristic

This paper presents a planar ultra-wideband (UWB) antenna with band rejection characteristic for UWB communications. A planar rectangular patch is printed on a PCB with epsiv=4.4 (FR4) and the volume of this antenna is 30times30times1.6 mm³. To obtain the band rejection characteristic, we made the partial ground with width of 30 mm and length of 2 mm on the other plane of the patch. By adding a branched feed line, we obtained increased bandwidth. Also, the addition of bevels on both edges of a rectangular patch increased the bandwidth. For the optimized parameters, simulations are performed by using ANSOFT HFSS. The average measured return loss is -8.2 dB in 3.1 ~ 4.8 GHz low band and it shows not so good characteristic. But band rejection characteristic in 4.9 ~ 6.8 GHz band shows better performance than the simulation. This antenna provides nearly same H-plane patterns at 5 GHz between the simulation and the measurement but it shows a marked difference at 6 GHz. And the group delay is less than 1.2 ns with a little variation except the maximum 4.2 ns at 7.17 GHz. If the return loss in low band can be improved, this proposed antenna will satisfy the UWB specifications of the MIC (ministry of information and communication) of Korea.