Conference Publications
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PublicationA wideband circularly polarized wearable antenna based on metasurface for WBAN applications(Institute of Electrical and Electronics Engineers (IEEE), 2022)This conference paper presents a circularly polarized wearable antenna array based on metasurface with wideband for wireless body area network (WBAN). The antenna array consists of four metasurface antennas, and each antenna has a sub array including 2 x 2 metasurface elements. A ring-shaped feeding structure with four arms is employed in this array. Using this structure, a quasi-90° phase delay is generated between each adjacent arm, and thus the antenna array can radiate a circularly polarized pattern. For the wearable antenna array, the simulation -10 dB impedance bandwidth is from 3 GHz to 5.92 GHz with 65.5% relative bandwidth. And the 3 dB axial ratio bandwidth is from 3 GHz to 5.45 GHz with 58% relative bandwidth. The whole size of the antenna array is 1.59λ×1.59λ×0.09λ (106×106×6 mm3) at 4.5 GHz, and the maximum gain is 8.3 dBi. Eventually, the Specific absorption rate (SAR) at different frequency of proposed antenna is assessed on the body phantom, and the values are satisfied the FCC standards. This flexible antenna array is an excellent candidate for WBAN and 5G applications.
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PublicationShielding efficiency study of sodium based chitosan polymer with different types of filler(Institute of Electrical and Electronics Engineers (IEEE), 2020)Sodium based chitosan (CH/Na) polymer was prepared with four different fillers and the suitability for electromagnetic interference (EMI) shielding were tested based on its electrical conductivity and shielding efficiency. The sodium based chitosan polymer was prepared by mixing the chitosan powder with sodium ion solution (Na) and the selected filler was added to the mixture in order to further improve the electrical properties of the composite. The fillers selected for this work were Copper (II) Selenite (CuSe), Iron (III) oxide (Fe3O4), Zinc Oxide (ZnO) and Fe-doped ZnO (FeZnO). Results show that using the Na and additional filler will increase the conductivity of pure chitosan film from reported 10-4 μS/cm to 10-5 S/cm. The CH/Na polymer with CuSe filler shows the highest electrical conductivity at 5.23×10-5 S/cm, followed by Fe3O4, ZnO and FeZnO. The CH/Na/CuSe polymer are also tested at different thickness with a high of 1.5 dB of shielding obtained. Increasing the (w/v)% of CuSe further increased the shielding efficiency to up to 19.55 dB.
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PublicationPerformance enhancement of semicircular shaped array antenna using metasurface(Institute of Electrical and Electronics Engineers (IEEE), 2020)This work studies the integration of a semicircular shaped array antenna into an Artificial Magnetic Conductor (AMC) which resonate at the desired operating frequency of 9.41 GHz. The proposed AMC performs as a high impedance surface with a high permeability (approximately 7.08) at 9.41 GHz, with a perfect magnetic conductor characteristic. As result, the AMC is able to be stacked adjacent to the semicircular shaped. The simulation results show that the AMC has successfully enhanced the gain and efficiency of the antenna to 9.55 dB and 97% respectively compared to 8.44 dB and 96% without AMC. Besides that, a slight bandwidth improvement, from 395 MHz to 398 MHz can be observed with the AMC. Both simulated and measured results show a good agreement in term of reflection coefficients and radiation patterns.
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PublicationInfluence of pre-sputtering technique on material properties of BST thin films for tunable microwave applications(Institute of Electrical and Electronics Engineers (IEEE), 2020)This paper focuses on the influence of pre-sputtering process on the material properties of RF sputtered Barium Strontium Titanate (BST) thin films. Ba0.5Sr0.5TiO3 thin films were synthesized on sapphire substrates via RF magnetron sputtering system for 2-, 3- and 4-hour deposition time. The samples were then post-annealed for 2 hours at 900 °C in conventional furnace and characterized using x-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron (FESEM) and energy dispersive x-ray (EDX). The AFM analysis revealed that the BST thin film of the 4-hour deposition time produces rougher surface due to larger grain size. All the XRD patterns observed to have intense (110) peaks, indicating the preferred orientation of the BST thin films. From the FESEM results, it is observed that the 3-hour deposited sample is denser and uniform compared to its 2-hour counterpart. However, the 4-hour deposited sample shows a non-uniform film. EDX analysis showed that the elemental composition of the 4-hour deposited sample is the closest to the ideal atomic concentration (at. %) of the BST thin film.
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PublicationA flexible wearable linear-to-circular polarizer for GNSS application(Institute of Electrical and Electronics Engineers (IEEE), 2020)This paper presents a single-layered fabric-based flexible linear-to-circular polarizer for GNSS application operating at 1.575 GHz. The structure presented here is based on a square aperture with an E-shaped patch structure on the reverse side. The size of the structure is 0. 21λ0 ×0. 26λ0 × 0. 01λ0 The complete structure is flexible, and the frequency of operation is centered at 1.575 GHz, with a minimum value of the axial ratio achieved is 0.06 dB. The 3 dB axial ratio fractional bandwidth is 3.81% (1.54-1.60 GHz) and the conversion efficiency fractional bandwidth covering 90% is 5.09% (1.53 to 1.61 GHz).