Taha A. Elwi

Multi-walled carbon nanotube-based RF antennas

A novel application that utilizes conductive patches composed of purified multi-walled carbon nanotubes (MWCNTs) embedded in a sodium cholate composite thin film to create microstrip antennas operating in the microwave frequency regime is proposed. The MWCNTs are suspended in an adhesive solvent to form a conductive ink that is printed on flexible polymer substrates. The DC conductivity of the printed patches was measured by the four probe technique and the complex relative permittivity was measured by an Agilent E5071B probe. The commercial software package, CST Microwave Studio (MWS), was used to simulate the proposed antennas based on the measured constitutive parameters. An excellent agreement of less than 0.2% difference in resonant frequency is shown. Simulated and measured results were also compared against identical microstrip antennas that utilize copper conducting patches. The proposed MWCNT-based antennas demonstrate a 5.6% to 2.2% increase in bandwidth, with respect to their corresponding copper-based prototypes, without significant degradation in gain and/or far-field radiation patterns.

Wearable Yagi microstrip antenna for telemedicine applications

This paper presents a button shaped antenna based on a microstrip Yagi array. The proposed antenna is suitable for Wireless Body Area Network (WBAN) and telemedicine applications operating at 2.45 GHz. Antenna properties, such as far-field radiation patterns, coupling coefficient, measured by the scattering parameter S11, and gain are provided. Moreover, the simulated performance of the proposed antenna is compared to circular and rectangular patch button shaped antennas having similar sizes. Design and simulations are performed using CST Microwave Studio software which is based on the Finite Integration Technique (FIT). The proposed antenna achieved a gain of 6.7 dB, (F/B) ratio of 11.7 dB and a semi-directional radiation pattern required for on body and off body applications.

A Miniaturized Lotus Shaped Microstrip Antenna Loaded with EBG Structures for High Gain-Bandwidth Product Applications

In this paper, the design of a printed circuit antenna based on lotus flower patch of a miniaturized profile is proposed. The antenna consists of three layers including a patch and a ground plane of a thin copper layer separated by a Roger RT/duroid R ©5880 substrate for high gain-bandwidth product applications including microwave imaging systems. The patch structure is patterned with triangular defects to provide a fractal structure. Nevertheless, the ground plane is defected with Electromagnetic Band Gap (EBG) structures. The antenna is found to show a first resonant mode around 3 GHz, while the other frequency modes are obtained around 4.2 GHz and 6GHz which are below −10 dB. Moreover, the antenna operates over the frequency range from 7.8 GHz up to 15 GHz with a bore-sight gain varing from 4dBi up to 6 dBi when operates in free-space environments. The antenna size is reduced to a 32mm×28mm×0.5 mm using shorting plates on the substrate edges. The antenna performance characteristics are examined using CST and HFSS commercial software packages, which are based on the Finite Integration Technique (FIT) and the Finite Element Method (FEM), respectively. Finally, the antenna performance is tested experimentally for both S11 spectrum and radiation patterns to show an excellent matching with the obtained numerical results.

A systematic approach for the design, fabrication, and testing of microstrip antennas using inkjet printing technology

We present a systematic approach for producing microstrip antennas using the state-of-the-art-inkjet printing technique. An initial antenna design based on the conventional square patch geometry is adopted as a benchmark to characterize the entire approach; the procedure then could be generalized to different antenna geometries and feeding techniques. For validation purposes, the antenna is designed and simulated using two different 3D full-wave electromagnetic simulation tools: Ansofts High Frequency Structure Simulator (HFSS), which is based on the Finite Element Method (FEM), and CST Microwave Studio, which is based on the Finite Integration Technique (FIT). The systematic approach for the fabrication process includes the optimal number of printed layers, curing temperature, and curing time. These essential parameters need to be optimized to achieve the highest electrical conductivity, trace continuity, and structural robustness. The antenna is fabricated using Inkjet Printing Technology (IJPT) utilizing Sliver Nanoparticles (SNPs) conductive ink printed by DMP-2800 Dimatix FujiFilm materials printer.

Miniaturized microstrip antenna array with ultra mutual coupling reduction for wearable MIMO systems

In this paper, a miniaturized microstrip antenna array with two patches is proposed for wearable MIMO systems. The array is designed to resonate at 4.2 GHz and 8.1 GHz for biomedical micro-sensing technology and biomedical diagnostics applications, respectively. In this paper, the use of a diagonal slot on the microstrip patch to reflect the surface current in a direction opposite to that of the neighboring patch. Moreover, the common area of the ground plane, between the two antennas, is augmented with Uniform Compact-Photonic Band Gap (UC-PBG) structures to prevent surface waves. This approach reduces the mutual coupling to −17 dB within a separation distance of 1.4 mm ≈ λ<inf>o</inf>/51, where λ<inf>o</inf> is the wavelength at 4.2 GHz. The microstrip antenna patch is consistent of rectangular part slotted with a diagonal trace and a meander trace which reduces the electrical size of the microstrip patch, when it is printed on substrate of ε<inf>r</inf> = 3.5, to λ<inf>o</inf>/18 × λ<inf>o</inf>/5. The maximum linear dimension of the antenna array is λ<inf>o</inf>/7.2 × λ<inf>o</inf>/4.3 × λ<inf>o</inf>/137. The performance of the array is characterized in terms of S-parameters, broadband gain and correlation spectra as well as the radiation patterns. The proposed antenna array provides bore-sight gain of −15.1 dBi at 4.2 GHz and −7.5 dBi at 8.1 GHz of 54.2 MHz and 81.8 MHz, respectively. The numerical model of the proposed array is simulated based on the Finite Integration Technique (FIT) using the Transient Domain (TD) solver of CST Microwave Studio.

Theory of Gain Enhancement of UC-PBG Antenna Structures Without Invoking Maxwell's Equations: an Array Signal Processing Approach

In this paper, a novel and computationally e-cient algorithm which combines Array Signal Processing (ASP) approach with Fourier Optics (FO) is developed in the realm of gain enhancement achieved by placing Uniplanar Compact-Photonic Band Gap (UC- PBG) structures on top of microstrip antennas. The proposed scheme applies FO to the well-known sampling theorem borrowed from Digital Signal Processing (DSP) analysis in the framework of ASP approach which we refer to as the FDA algorithm. The FDA algorithm is suitable for lossless UC-PBG structures with 1- D, 2-D and 3-D lattice of canonical geometrical apertures, such as circular, octagonal, hexagonal, and square. In order to validate the proposed approach, two difierent UC-PBG structures of octagonal and circular apertures are considered at 2.6GHz. The UC-PBG structures under consideration consist of two layers positioned above a microstrip antenna; each layer is an array of 9 £ 9 apertures separated by half of the focal length distance of the lens in the near- fleld of the microstrip antenna. The performance of the microstrip antenna with and without the UC-PBG is reported using numerical simulations performed using CST Microwave Studio (CST MWS) based on the Finite Integration Technique (FIT). The radiation patterns and directivity of the microstrip antenna based on UC- PBG structures are evaluated using the proposed FDA algorithm and

A PASSIVE WIRELESS GAS SENSOR BASED ON MICROSTRIP ANTENNA WITH COPPER NANORODS

Applications of copper (Cu) nanorod arrays, produced by glancing angle deposition (GLAD) technique, which extends the function of conventional microstrip antennas to encompass passive wireless gas sensors at microwave frequencies are presented. The proposed microstrip antenna consists of Cu nanorod arrays grown on silicon wafers which were coated with thin fllms of Cu of 50nm in thickness. To study the efiect of the length of Cu nanorods on antenna performance, Cu nanorods of difierent lengths (400, 700, and 1000nm) were fabricated. The efiects of Cu nanorods morphologies (Cu thin fllm, closely-spaced Cu nanorods, and well-separated Cu nanorods), were investigated too. Conventional microstrip antennas based on sputtered Cu thin fllm were prepared for comparison. It was found that as the length of Cu nanorods increases, the antennas exhibit a wider bandwidth and lower frequency resonance than those of the conventional antennas based on Cu thin fllm. Furthermore, moving from ∞at surface to well-separated nanorods results in a decrease in the resonant frequency, while there was no observable efiect on the bandwidth. These enhancements are attributed to the mutual coupling occurring among Cu nanorods. Based on the antenna characterization, the 1000nm long Cu nanorods sample was selected for gas detection measurements due to its observed sharp resonance and narrow bandwidth. The detection mechanism is based on the change of in the magnitude of the re∞ection coe-cient as well as the resonant frequency due to the introductions of difierent gases. The proposed sensor based on Cu nanorods shows a signiflcant response in

Enhanced Low-Angle GPS Coverage Using Solid and Annular Microstrip Antennas on Folded and Drooped Ground Planes

Folded and drooped microstrip antennas are investigated in this communication for their potential applications in GPS marine navigation. Numerical and experimental results are reported to identify the effects of the percentage of the patch extending around to the folded side, position, and angle of the bend on the performance of the proposed antennas in comparison to the conventional flat counterparts. The folded antennas provide marginally improved 3-dB beam width and excellent phase center stability without degrading the bore-sight gain. A novel drooped square annular element operating in the TM 30 mode is proposed and validated both numerically and experimentally. The drooped annular antenna is shown to have substantially improved above-horizon coverage to suit applications requiring acquisition of satellites from horizon to horizon with a pattern ripple less than 2 dB over the upper hemisphere and with an impedance bandwidth of 2%. The polarization rejection is marginally degraded at bore-sight. At the horizon, the cross component becomes dominant by 1.5 dB.

No Frequency Reuse: Wearable Steerable MIMO Microstrip Antenna Array for Mobile Ad Hoc Applications

Aim: The principle of eliminating the frequency reuse in the mobile Ad Hoc system among the sectors of theunit cell using Multi Inputs Multi Outputs (MIMO) antenna array is investigated in this paper. Antenna Design: The size of the proposed antenna array is 10◊10 cm 2 to obtain a bandwidth around 1 GHz. The single antenna element is constructed from sub -patches that are connected with feeding network through pin diodes, as switches, that are mounted on an FR-4 substrate. Antenna Performance :The antenna elements are characterized from 0.8 GHz to 2 GHz in terms ofS-parameters and radiation patterns with differ ent switching OFF/ON categories. Methodology: A numerical investigation based on Finite Integral Techniques (FIT) of Time Domain (TD) formulations is conducted using CST MWS to evaluate the antenna performance. A Frequency Domain (FD) solver based on CST f ormulations is conducted for validation. Original ResearchArticle

Electromagnetic wave interactions with 2D arrays of single-wall carbon nanotubes

We report, for the first time, the scattering, absorption, and reflection characteristics of 2D arrays of finite-length, armchair, single-walled carbon nanotubes (SWNTs) in the visible frequency regime. The analysis is based on the Finite-Element-Method formulation of Maxwells equations and a 3D quantum electrical conductivity function. Three geometrical models have been considered: solid cylinder, hollow cylinder, and honeycomb. We demonstrate that classical electromagnetic theory is sufficient to evaluate the scattering and absorption cross sections of SWNTs, which revealed excellent agreement againstmeasurements without the need to invoke the effective impedance boundary conditions. The solid and hollow cylindrical models fail to provide accurate results, when both scattering and absorption are considered. Finally, it is shown that reflection and transmission characteristics of both individual and arrays of SWNTs, which are essential for solar cell applications, are strongly influenced by the length and the phenomenological parameters of the SWNT.