Design methodology of the fractal annular ring antennas with the wideband operation

In this paper, a novel annular ring antenna is proposed to achieve a multi-wideband antenna. The structure is annular ring. For systematic design of the antenna, fractal shape is employed. Each iteration of the structure acts as a matching load for the previous section. Consequently, by increasing the electrical current path, multi-band and wideband performances can be achieved. For tuning the frequency bands, three slots are cut from the ground plane. The first operating band is from 1.47 GHz to 1.86 GHz (fractional band width (FBW): 23.42%), the second band is from 2.44 GHz to 3.51 GHz (FBW: 35.96%), and the third one is from 4.49 GHz to 5.34 GHz (FBW: 17.29%). Furthermore, the antenna has the ability to cover the ultra-wideband (UWB) spectrum by inserting two vias in the substrate. Using vias, impedance matching of the antenna is improved in the frequency range from 2.8 GHz to 5 GHz (FBW: 56.4%) with criteria |S-11|<-10 dB. Also, it has a noticeable impedance bandwidth (FBW: 117%) from 1.3 GHz to 5 GHz with criteria |S-11|<-6 dB. A prototype of the proposed antenna is fabricated and tested. The measurement and simulation results are in good agreement.