A Band-Notched UWB Antenna Loaded with Tree-Shaped Fractal

The design of a band-notched antenna for UWB applications is based on a 2nd- order T -shaped fractal configuration and distribution loading. The proposed antenna consists of a tree-shaped fractal patch with two extra strips added on each top of the T -shaped branches and a rectangular slot etched on the ground. With all optimized parameters by simulation, there are two resonant frequencies from 2.75 to 6.14GHz and a block band from 3.7 to 4.2GHz. With a polygon strip introduced between two tree-arms, the simulated and measured results present that the notch function covering all 5.2/5.8G WLAN and 4G C-bands as well as 5G band could be achieved. The peak gain in the notch band and the radiation efficiency in the pass- band are discussed through the analysis of the surface current distributions and E / H - plane radiation patterns at different frequencies. In addition to loading strips, we also tried to introduce separated rectangular slits or a complicated and interlinked slit into the tree-shaped branches. The influences of the slit width and length on the performances of the designed antennas are analyzed in detail.