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Title:	Development of uni-planar electromagnetic band gap structures for microstrip antenna systems
Authors:	Md. Shahidul Alam (P59306)
Supervisor:	Mohammad Tariqul Islam, Prof. Dr.
Keywords:	Microstrip Antennas Antennas (Electronics) Design and construction Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	17-May-2013
Description:	Microstrip patch antennas are very popular in mobile and radio wireless communication systems because of their well-known advantages of low profile, light weight, conformal to carrier and easy production. However, in addition to their inherent lack of gain, bandwidth etc., the excitation of surface wave reduces antenna efficiency and gain, results in poor antenna performances. Besides, it limits the operating bandwidth and give rise to mutual coupling between neighboring elements of a patch antenna array. Electromagnetic band gap (EBG) structures, which regarded as a special type of metamaterials, have become a significant breakthrough for overcoming these limitations of antennas. This research emphasis on designing compact wideband uni-planar EBG structures due to their structural easiness and suitability for designing completely planar antennas and other microwave circuitry. However, integration of EBG with antenna is a challenging work as an improper combination of these two opposite resonant structures may drastically degrade the antenna performances. This thesis focuses on the design and development of three different uni-planar type EBG structures and their applications for enhancing microstrip antenna performances by suppressing the surface waves. These analyses are performed by the commercially available 3D full-wave, finite element method based electromagnetic simulator Ansoft’s HFSS™ and fabricated prototypes of the designed structures were followed by numerous parametric measurements. The EBG characteristics are examined by reflection phase analysis, directive transmission and suspended microstrip line methods and then the EBG-antennas are configured and performances are compared. The first EBG is designed with square patches and meandered line interconnecting bridges (named as MLB-EBG), which has a wide band gap of 2.3 GHz (2.55 - 4.85 GHz) at 3.6 GHz. The second design is realized with concentric square patch surrounded by ring-slot (CSPRS) and it shows dual band gap of 4.04 GHz (1.59 - 5.63 GHz) and 3.54 GHz (9.52 - 13.06 GHz). In the third design, another dual wide band EBG is proposed which incorporates cross slots, thin connecting bridges and rectangular patches surrounded by split-ring-slots and it is referred to as SRS-EBG. The SRS-EBG band gaps are 4.29 GHz (5.11 - 9.4 GHz) and 5.31 GHz (10.54 - 15.85 GHz). The CSPRS-EBG is applied to a newly designed dualband CPW-fed antenna, where it acted as a reflecting surface and improved antenna’s radiation performances as well as the gain and bandwidth. The SRS-EBG prove to be effective as an artificial ground of an umbrella-shape monopole antenna, which obtained 360 MHz more bandwidth and 1.2 dB higher gain than the conventional one. Furthermore, the SRS-EBG and the MLB-EBG structures reduced mutual coupling in two different arrays by 20 dB approximately, and enhanced the array performances. The experimental results matched pretty well with the simulated results and demonstrate the efficacy and aptness of the proposed designs.,Master of Science
Pages:	130
Call Number:	TK7871.6.A433 2013 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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