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Comparison Of Different Planar Monopole UWB Antenna Using HFSS
« on: November 23, 2011, 06:34:14 am »
Author : Ria Kalra , Sukhdeep Kaur
International Journal of Scientific & Engineering Research Volume 2, Issue 10, October-2011
ISSN 2229-5518
Download Full Paper : PDF

Abstract - Since the release by the Federal Communications Commission (FCC) of a bandwidth of 7.5GHz (from 3.1GHz to 10.6GHz) for ultra wideband (UWB) wireless communications, UWB is rapidly advancing as a high data rate wireless communication technology. As is the case in conventional wireless communication systems, an antenna also plays a very crucial role in UWB systems. However, there are more challenges in designing a UWB antenna than a narrow band one. A suitable UWB antenna should be capable of operating over an ultra wide bandwidth as allocated by the FCC. At the same time, satisfactory radiation properties over the entire frequency range are also necessary. This paper focuses on UWB antenna design and analysis. Extensive investigations were also carried out on  different types of Planar Monopole UWB antennas .The first type of antenna studied in this paper is circular disc monopole antenna. The disc monopole originates from conventional straight wire monopole by replacing the wire element with a disc plate to enhance the operating bandwidth substantially .Based on the understanding of circular disc monopole, different compact versions featuring low-profile and compatibility to printed circuit board are proposed and studied. All of them are printed disc monopoles, fed by a micro-strip line .Investigations have also been carried out in this thesis to analyze  the design parameters of different monopole antenna such as planar circular monopole antenna, planar ring monopole antenna, modified planar rectangular antenna with and without notch. It has been demonstrated that these antennas are suitable for UWB applications
          Index Terms— High frequency structure simulator (HFSS), modified rectangular antenna, planar circular monopole antenna (PCMA), planar ring monopole antenna(PRMA), power density spectrum (PDS), ultra wide-band(UWB).
Present time is witnessing a very rapid growth of wireless communications, for which antennas with very large bandwidth are in strong demand, so that various applications are covered with fewer or preferably with a single antenna.
It will be preferred that an antenna has bandwidth in excess of frequency range from 800MHz to 11GHz or even more, to include all the existing wireless communication systems such as AMPC800, GSM900, GSM1800,PCS1900,WCDMA/UMTS (3G), 2.45/5.2/5.8-GHz-ISM, UNII,DECT, WLANs, European  Hiper LAN I, II, and UWB (3.1–10.6GHz). Out of all the above-mentioned wireless systems, ultra-wide bandwidth (UWB) wireless technology is most sought for very high-data-rate and short-range wireless communication systems, coding for security and low probability of interception, rejection of multipath effect, modern radar systems, and so forth. As mentioned above, this technology uses ultra-wide bandwidth of 7.5 GHz, ranging from 3.1GHz to 10.6GHz.

One of the challenges for the implementation of UWB systems is the development of a suitable or optimal antenna.The first important requirement for designing an UWB antenna is the extremely wide impedance bandwidth. In 2002, the US FCC allocated an unlicensed band from 3.1GHz to 10.6GHz on the frequency spectrum for UWB applications. Hence, up to 7.5GHz  of bandwidth is required for a workable UWB antenna. And commonly, the return loss for the entire ultra-wide band should be in the criterion of less than -10dB.

Next, for indoor wireless communication, omnidirectional property in radiation pattern is demanded for UWB antenna to enable convenience in communication between transmitters and receivers. Therefore, low directivity is desired and the gain should be as uniform as possible for different directions. Another important requirement is the radiation efficiency.Since the power transmitted into space is very low, the radiation efficiency is required to be quite high.Moreover, linear phase in time domain characteristics is desired for UWB application. Since linear phase will produce constant group delay, the transmitted signals, in the form of extremely short pulses, will not be distorted and hence the system works effectively. Last but not least, since UWB technology is mainly employed for indoor and portable devices, the size of the UWB antennas is required to be sufficiently small so that they can be easily integrated into various equipments.

Planar and printed monopole antennas are the good candidates for use in UWB wireless technology because of their wide impedance bandwidth and nearly omnidirectional azumuthal radiation pattern. Many shapes of planar, also known as planar disc, monopole antennas are reported, which yield very large bandwidth. Some of these reported configurations have bandwidth in excess of that required for UWB application.Printed monopole antennas (PMAs) are truly planar and have radiation patterns similar to that of a dipole antenna.These monopoles can be integrated with other components on printed circuit board, have reduced size on dielectric substrate,and are easy to fabricate. Printed antennas, commonly fabricated on FR4 substrate, are very cost effective, which is ideally suited for UWB technology-based low-cost systems.

This paper focuses on UWB planar printed circuit board (PCB) antenna design and analysis. Extensive investigations are carried out on the development of different planar UWB antennas . Firstly, the planar circular antenna designs for UWB system is introduced and described. Secondly, printed UWB circular ring monopoles were realized by replacing the disc elements of planar circular disc monopole antennas with circular ring elements.Next is the design of modified rectangular antenna with and without notch.All the antenna designs mentioned above cover the UWB range of 3.1-10.6 GHz.

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