UWB Fractal Antennas with Low Group Delay Variation

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UWB Fractal Antennas with Low Group Delay Variation Bazil Taha Ahmed1   · Daniel Brande Hernández1

© Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract In this paper, two Sierpinski carpet UWB fractal antennas are designed and fabricated. The first fractal antenna is an antenna that has not any notch filter. The second one is an antenna with double notch filters. Antenna without notch filter has an operating band of (3.1–10.8) GHz with a gain of 5.3  dB at 10  GHz. This antenna has a low group delay variation. Antenna with double notch filters working at (3.36–12) GHz band shows a gain reduction and higher group delay at the filters operating band. Out of the notch filters operating band, the antenna has a low group delay variation and a gain near to the gain of the antenna without notch filters. The MIMO version of the antenna shows an operating band up to 10.8 GHz and isolation between ports higher than 15 dB. Keywords  UWB antenna · Fractal antenna · Band notched antenna

1 Introduction Ultra-wideband (UWB) systems are systems whose absolute bandwidth is 500  MHz or higher. Communication system can be also considered as UWB if its relative bandwidth is 20% or higher. The best moments of the UWB investigation started at 2002 when the Federal Communications Commission (FCC) designated the (3.1–10.6) GHz band for UWB communications [1]. UWB antennas can be designed in different form such as dipole, monopole or a logarithmic antenna. Logarithmic antennas have usually a moderate gain of 6–10  dB while monopole UWB antennas without reflectors has a gain of 2–6 dB. A compact form of monopole UWB antennas is the UWB fractal UWB monopole antenna. In last years, investigators show a great interest in the utilization of fractal geometry antennas as a part of the communication systems transceivers. Due to the shape properties of the fractal antennas, they exhibit multiband operation that can be used to build UWB antennas. This was the motivation behind our study to fractal antenna performance and the investigation if it can be used as an antenna with low group delay variation. UWB communication systems operating at the huge band of (3.1–10.6) GHz are easily interfered by one or more of the nearby narrowband or large band communication systems * Bazil Taha Ahmed [email protected] 1



Escuela Politécnica Superior, Universidad Autónoma de Madrid, 28049 Madrid, Spain

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B. T. Ahmed, D. B. Hernández

such as WLAN system operating at the lower part (5.15–5.35  GHz) or the higher part (5.725–5.825  GHz) of the (5.15–5.825) GHz band, and X-band satellite downlink communication frequency operating at (8.1–8.5) GHz. The interferences of UWB systems with these communication systems can be avoided by using the traditional technique building a band reject filer as embedded part of the UWB receivers. In low cost receivers, this solution is un economical since increases the complexity and the size of the UWB receiver. The best way to reduce the effect the mutual interference with other