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Rahim N.A.A.,Microwave Technology Center | Kara M.H.,ElecTronic Center | Mahmood M.R.,University Technology of MARA
2014 IEEE Asia-Pacific Conference on Applied Electromagnetics, APACE 2014 - Proceeding | Year: 2015

The experimental results for high-frequency characteristics (from 2 to 20 GHz) of graphene films are presented. Samples with multi-layer graphene were fabricated and characterized from curve-fitting experimental results with values simulated using an electromagnetic simulator. From RF two-port network experiments, the circuit parameters of capacitance, resistance and inductance were extracted using a physics-based RLC lumped element circuit model that consists of contact pads and graphene electrodes using a commercially available microwave circuit simulator. The proposed model reproduced all the measured characteristics, and the component values which gave the best fit with the measurements were successfully extracted from the model. Our findings demonstrate that the measured RF performance of multilayer graphene (MLG)-based transmission lines gave good agreement with simulation predicted by a lumped element RLC model. © 2014 IEEE. Source

Awang Teh A.,Microwave Technology Center | Awang Teh A.,University Technical Malaysia Melaka | Ahmad R.,Microwave Technology Center | Kara M.,Microwave Technology Center | And 3 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2012

We report the use of a new precursor as active agents to promote the growth of carbon nanotubes (CNT) in methane ambient using a simple thermal chemical vapour deposition method. The agents consist of ammonia and methanol mixed at different ratios and was found to enhance the growth of CNTs. The optimum methanol to ammonia ratio was found to be 8 to 5, whereby longer and denser CNTs were produced compared to other ratios. The result was found otherwise when the experiment was done solely in methane ambient. In addition, CNT growth on substrates coated with double layer Ni catalyst was improved in terms of quality and density compared to a single coated substrates. This finding is supported by Raman spectrometry analysis. Copyright © 2012 American Scientific Publishers. All rights reserved. Source

Wahab N.A.,Microwave Technology Center | Salleh M.K.M.,Microwave Technology Center | Khanfar S.K.M.,Microwave Technology Center | Khan Z.I.,Microwave Technology Center | Awang Z.,Microwave Technology Center
Progress in Electromagnetics Research Letters | Year: 2013

A single-side-access ring resonator topology is presented. It employs a single quarter-wavelength coupled-line that couples to a one-wavelength ring to exhibit a single-mode resonance with transmission zeros. A global synthesis is presented, in order to control the transmission zeros in its response. As the transmission zeros of the ring resonator maintains their positions when multiple identical rings are used, the global synthesis can further be used for the design of higher order filters with multiple rings. Furthermore, since only one coupled-line is used in the resonator topology, only one section of line is present in the ring, other than the coupled-line. Hence, there will be no second section of the ring that needs to be adjusted to obtain the symmetrical response during its realization, as compared to other types of ring topologies. To show the advantage of the synthesis, it is applied in the design of higher order ring-based bandpass filters, which also involve extra quarter-wavelength coupled-lines to create additional poles. Five bandpass ring filters up to 5th-order were realized using microstrip technology, and measured to validate the proposed concept. Measurement results showing good agreement with those from the simulation are also presented throughout the paper. Source

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