Defected Waveguide Structure With Circular Monopole Antenna For Ultrawideband Applications

Chin, Shu Jia (2019) Defected Waveguide Structure With Circular Monopole Antenna For Ultrawideband Applications. Masters thesis, Universiti Teknikal Malaysia Melaka.

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The next generation wireless communication claims for high resolution and high data rate which lead toward the highest level of exploring to the operating bandwidth. To overcome this demand, researches have been concerned on the wideband antenna to be assembled in one system to support all the possible frequency range. Monopole antenna appeared to be often-considered candidate due to low cost and low profile for the portable devices. Yet, it performed poor gain. Furthermore, the defected structure was noticed to design on ground plane and microstrip feed line as Defected Ground Structure (DGS) and Defected Microstrip Structure (DMS), respectively but not yet in waveguide as Defected Waveguide Structure (DWS). Thus, the project aimed to design, simulate and fabricate monopole antenna with DWS. The antenna design was constructed in CST Microwave Studio. The effects of DWS toward monopole antenna were investigated through antenna parameters such as reflection coefficient, gain, directivity, efficiency and radiation pattern. Besides on antenna parameters, transmission coefficient of the DWS was also simulated and measured. The simulated results for example reflection coefficient, gain and radiation pattern were verified by measured results. The simulated S-Parameters results of DWS were also modelled. The equivalent circuit was used to model the stop band and pass band characteristics of simulated S-Parameters based on filter concepts in the Advanced Design System (ADS) software. Initially, both monopole antennas achieved wide bandwidth more than 8 GHz with two resonance frequencies around 3 GHz and 9 GHz. With the FR4 waveguide, the performances of monopole antenna were remained with slightly higher gain and directivity achieved. Meanwhile, monopole antenna with waveguide showed multiband in narrower bandwidth less than 5 GHz and significant high directivity more than 8 dB. DWS has been designed in single element, connected element and hybrid element. Generally, almost all monopole antenna with DWS showed improvement on gain and directivity with maximum enhancement achieved up to 4 dB. At the meantime, wideband characteristics more than 8 GHz and efficiency more than –3 dB were presented. Both the resonance frequencies of monopole antennas were shifted slightly. The second resonance frequency shifted around 0.5 GHz when DWS was added on externally. Meanwhile, the performance of monopole antenna with DWS in connected element was slightly different compared to others monopole antenna with DWS. Fluctuated reflection coefficient with higher gain more than 5 dB and directivity more than 7 dB was observed around 2 – 5 GHz. DWS designs improved the overall gain and directivity at the same time maintained wideband characteristics and high efficiency of monopole antenna. The DWS could be used as a platform for the future communication system based on smart system technology.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Monopole antennas, Radio frequency modulation, Antenna radiation patterns, Waveguide Structure, Circular Monopole Antenna, Ultrawideband
Subjects: T Technology > T Technology (General)
T Technology > TK Electrical engineering. Electronics Nuclear engineering
Divisions: Library > Tesis > FKEKK
Depositing User: F Haslinda Harun
Date Deposited: 22 Oct 2020 14:52
Last Modified: 22 Oct 2020 14:52
Statistic Details: View Download Statistic

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