A Novel Hybrid Fractal Antenna Design for Ultra-Wideband Application

摘要

In this article, the up-to-date design of an antenna in the shape of Chakana, “Andes Cross” or “Inka Cross” will be presented and meticulously analyzed. The design base-structure is a planar monopole that goes along with different modifications related to fractal geometry concepts due to its main properties miniaturization, operability, self-similarity, and space-filling. The utilization of the second iteration of Koch fractal in the ground plane and Sierpinski second iteration in the patch allows an improvement of the Ultra-Wideband (UWB)characteristics by acquiring reflection in all of the 3.1 to 10.6 GHz range designated by the Federal Communications Commission (FCC). In order to improve the reflection present in high frequencies a ground-plane Notch is used; furthermore, so as to reject the frequency band considered for IEEE 802.11A, WLAN-HIPERLAN/2 and the Industrial, Scientific and Medical band (ISM band)located between 5.15 and 5.82 GHz, the implementation of an H-shaped Notch filter on the patch is carried out. The dimensions optimized for this fractal antenna are 30mm×33mm, mounted on an FR4 substrate with dielectric constant εr=4.4, a thickness of h=1.5 and a tangent of losses of δ=0.02, obtaining a bandwidth of 3.25 to 11.36 GHz with a VSWR<;2 over the entire frequency range except for the rejected frequencies for ISM. Also, the H-Shaped Notch filter with an effective length of approximately 23.14 mm is positioned around of 4 mm from the feed line to ensure an optimal rejection of -4.85 dB at the center frequency of 5.41 GHz. Therefore, based on the combination of the fractal geometries Koch and Sierpinski proposed, a new Hybrid Fractal Antenna Design for UWB application with a nearly omnidirectional radiation pattern, adequate 50 impedance and good return loss less than -10dB over the entire UWB range is presented.