UWB monopole antenna with multiple fractal slots for band-notch characteristic and integrated Bluetooth functionality

This article presents the design of compact microstrip-fed modified half annular-shaped planar monopole antenna for ultra-wideband (UWB) (3.1–10.6 GHz) application. An electromagnetically coupled circular-shaped parasitic patch is introduced at the backside of the substrate to enhance the bandwidth of the whole antenna by shifting the lower frequency band. A rectangular slot-embedded ground plane at the bottom surface of the substrate improves the impedance bandwidth with excellent matching characteristics for the entire design frequency band. In addition to this, a half Minkowski fractal slot, a hybrid fractal slot, and Sierpinski arrowhead curve fractal slot are coupled to the feed line individually such that three UWB antennas with band-notched characteristic are realized that mitigate the interference between UWB and Wireless local area network (5.15–5.825 GHz) assigned to IEEE 802.11a and HIPERLAN/2 can be reduced. Now to increase the functionality of the antenna, a second iterated fractal binary tree is embedded on the patch to excite resonant mode centered at 2.45 GHz for the Bluetooth band. The proposed antenna exhibits omnidirectional radiation pattern and constant gain characteristics over the desired frequency band except the notch band. Prototypes of variants are fabricated and measured results agree well with simulation.