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  • Articles  (201)
  • Latest Papers from Table of Contents or Articles in Press  (201)
  • 2010-2014  (201)
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  • Articles  (201)
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  • Latest Papers from Table of Contents or Articles in Press  (201)
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  • 1
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    Ultrawideband Noise Radar Imaging of Impenetrable Cylindrical Objects Using Diffraction Tomography (2014)
    Hindawi
    Details
    Publication Date: 2014-12-26
    Description: Ultrawideband (UWB) waveforms achieve excellent spatial resolution for better characterization of targets in tomographic imaging applications compared to narrowband waveforms. In this paper, two-dimensional tomographic images of multiple scattering objects are successfully obtained using the diffraction tomography approach by transmitting multiple independent and identically distributed (iid) UWB random noise waveforms. The feasibility of using a random noise waveform for tomography is investigated by formulating a white Gaussian noise (WGN) model using spectral estimation. The analytical formulation of object image formation using random noise waveforms is established based on the backward scattering, and several numerical diffraction tomography simulations are performed in the spatial frequency domain to validate the analytical results by reconstructing the tomographic images of scattering objects. The final image of the object based on multiple transmitted noise waveforms is reconstructed by averaging individually formed images which compares very well with the image created using the traditional Gaussian pulse. Pixel difference-based measure is used to analyze and estimate the image quality of the final reconstructed tomographic image under various signal-to-noise ratio (SNR) conditions. Also, preliminary experiment setup and measurement results are presented to assess the validation of simulation results.
    Print ISSN: 1687-5826
    Electronic ISSN: 1687-5834
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 2
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    A New Method of Designing Circularly Symmetric Shaped Dual Reflector Antennas Using Distorted Conics (2014)
    Hindawi
    Details
    Publication Date: 2014-12-18
    Description: A new method of designing circularly symmetric shaped dual reflector antennas using distorted conics is presented. The surface of the shaped subreflector is expressed using a new set of equations employing differential geometry. The proposed equations require only a small number of parameters to accurately describe practical shaped subreflector surfaces. A geometrical optics (GO) based method is used to synthesize the shaped main reflector surface corresponding to the shaped subreflector. Using the proposed method, a shaped Cassegrain dual reflector system is designed. The field scattered from the subreflector is calculated using uniform geometrical theory of diffraction (UTD). Finally, a numerical example is provided showing how a shaped subreflector produces more uniform illumination over the main reflector aperture compared to an unshaped subreflector.
    Print ISSN: 1687-5826
    Electronic ISSN: 1687-5834
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 3
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    Multifrequency Oscillator-Type Active Printed Antenna Using Chaotic Colpitts Oscillator (2014)
    Hindawi
    Details
    Publication Date: 2014-12-01
    Description: This paper presents a new concept to realize a multifrequency Oscillator-type active printed monopole antenna. The concept of period doubling route to chaos is exploited to generate the multiple frequencies. The chaotic Colpitts oscillator is integrated with the printed monopole antenna (PMA) on the same side of the substrate to realize an Oscillator-type active antenna where the PMA acts as a load and radiator to the chaotic oscillator. By changing the bias voltage of the oscillator, the antenna can be made to operate at single or multiple frequencies. To test the characteristics of the antenna at single and multiple frequencies of operation, two similar prototype models of printed monopole broadband antennas are developed. One of these antennas used at transmit side is fed by the chaotic Colpitts oscillator while the other is used as the receive antenna. It is observed that the antenna receives single or multiple frequencies simultaneously for particular values of the bias voltage of the oscillator at the transmit end.
    Print ISSN: 1687-5826
    Electronic ISSN: 1687-5834
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 4
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    Design and Investigation of Disk Patch Antenna with Quad C-Slots for Multiband Operations (2014)
    Hindawi
    Details
    Publication Date: 2014-11-20
    Description: An investigation into the design and fabrication of multiband disk patch antenna with symmetrically quad C-slots is presented in this paper. The proposed antenna shows multiband resonance frequencies which highly depend on substrate thickness, dielectric constant, and radius of the disk patch. By incorporating two pairs of C-slots in optimum geometry on the radiating patch, the proposed antenna operates between 2 and 12 GHz at different frequency bands centered at 2.27, 7.505, 9.34, 10.33, and 11.61 GHz. The other antenna parameters are studied like gain, antenna efficiency, and radiation pattern. The proposed antenna may find applications in S-, C-, and X-band. The results are carried out with the aid of HFSS and MOM-based IE3D simulator. The measured and simulated results are in good agreement with each other.
    Print ISSN: 1687-5826
    Electronic ISSN: 1687-5834
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 5
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    Lossy-Transmission-Line Analysis of Frequency Reconfigurable Rectangular-Ring Microstrip Antenna (2014)
    Hindawi
    Details
    Publication Date: 2014-11-14
    Description: An analytical model for a frequency reconfigurable rectangular-ring microstrip antenna is proposed. The resonant frequencies and input impedance of the reconfigurable antenna are analyzed using a lossy-transmission-line (LTL) model. By making use of -admittance matrices, a formulation for the input impedance is analytically derived. The structure of the frequency reconfigurable antenna consists of a rectangular-ring shaped microstrip antenna which is loaded with a rectangular patch in the middle of the rectangular-ring antenna and fed by a microstrip line. RF switches are applied to connect the load to the antenna in order to reconfigure the operating frequencies. By modeling the antenna into a multiport equivalent circuit, the total input impedance is analytically derived to predict the resonant frequencies. To verify the analysis, the model input impedance and reflection coefficient calculation have been compared with the full-wave simulation and measurement results. The proposed model shows good agreement with full-wave simulated and measured results in the range of 1–3 GHz.
    Print ISSN: 1687-5826
    Electronic ISSN: 1687-5834
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 6
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    Selection of Microstrip Patch Antenna Substrate for WLAN Application Using Multiple Attribute Decision Making Approach (2014)
    Hindawi
    Details
    Publication Date: 2014-10-23
    Description: This paper presents a material selection approach for selecting microstrip patch antenna substrate for WLAN applications using multiple attribute decision making (MADM) approach. In this paper, different microwave dielectric materials for substrate and their properties like relative permittivity, quality factor, and temperature coefficient of the resonant frequency are taken into consideration and MADM approach is applied to select the best material for microstrip patch antenna. It is observed that Pb0.6Ca0.4ZrO3 is the best material for the antenna substrate in MPA for WLAN applications. It was observed that the proposed result is in accordance with the experimental finding thus justifying the validity of the proposed study.
    Print ISSN: 1687-5826
    Electronic ISSN: 1687-5834
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 7
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    Low Actuation Voltage RF MEMS Switch Using Varying Section Composite Fixed-Fixed Beam (2014)
    Hindawi
    Details
    Publication Date: 2014-10-21
    Description: The present authors have earlier reported the employment of varying section fixed-fixed beam for achieving lower pull-in voltage with marginal fall in restoring force. Reducing Young’s modulus also reduces the pull-in voltage but with lesser degree of reduction in restoring force. Composite beams are ideal alternatives to achieve decreased Young’s modulus. Hence new varying section composite fixed-fixed beam type RF MEMS switch has been proposed. The main advantage of this RF MEMS switch is that lower pull-in voltages can be achieved with marginal fall in stiction immunity. Spring constant of the proposed switch has been obtained using simulation studies and it has been shown that the spring constant and therefore the pull-in voltage () can be considerably reduced with the proposed switch. Simulation studies conducted on the proposed switch clearly demonstrate that the pull-in voltage can be reduced by 31.17% when compared to the varying section monolayer polysilicon fixed-fixed beam. Further this approach enables the designer to have more freedom to design lower pull-in voltage switches with improved stiction immunity.
    Print ISSN: 1687-5826
    Electronic ISSN: 1687-5834
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 8
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    Novel Design of Microstrip Antenna with Improved Bandwidth (2014)
    Hindawi
    Details
    Publication Date: 2014-10-03
    Description: A novel design of broadband patch antenna is presented in this paper. The broadband property of the proposed antenna is achieved by choosing a proper selection of dimensions and positions of slot and notch on the radiating patch. The bandwidth of the proposed antenna is found to be 30.5% with operating frequency band from 1.56 GHz to 2.12 GHz. Antenna characteristics are observed for different inclination angles “α” and its effect on bandwidths is also reported. The maximum gain of the antenna is found to be 9.86 dBi and it achieves broadside radiation pattern in the direction of maximum radiation over the operating band. The proposed antenna structure is simulated, fabricated, and tested for obtaining the desired performance. The simulated results are verified with experimental results which are in good agreement.
    Print ISSN: 1687-5826
    Electronic ISSN: 1687-5834
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 9
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    Development of a Novel Switched-Mode 2.45 GHz Microwave Multiapplicator Ablation System (2014)
    Hindawi
    Details
    Publication Date: 2014-09-24
    Description: The development of a novel switched-mode 2.45 GHz microwave (MW) multiapplicator system intended for laparoscopic and open surgical thermoablative treatments is presented. The system differs from the other synchronous and asynchronous commercially available equipments because it employs a fast sequential switching (FSS) technique for feeding an array of up to four high efficiency MW applicators. FSS technology, if properly engineered, allows improving system compactness, modularity, overall efficiency, and operational flexibility. Full-wave electromagnetic (EM) and thermal (TH) simulations have been made to confirm the expected performances of the FSS technology. Here we provide an overview of technical details and early ex-vivo experiments carried out with a full functional β-prototype of the system.
    Print ISSN: 1687-5826
    Electronic ISSN: 1687-5834
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 10
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    A Novel Wideband Miniaturized-Element Frequency Selective Surface (2014)
    Hindawi
    Details
    Publication Date: 2014-09-22
    Description: This letter presents a novel wideband miniaturized-element frequency selective surface (MEFSS). The simulation and measurement results show that the bandwidth of the proposed MEFSS is remarkably enhanced compared to that of an original second-order MEFSS while its size and total thickness are still small. A parametric study is also conducted to understand the operating mechanism of the proposed structure. The phenomenon observed in the parametric study is explained with an equivalent circuit model.
    Print ISSN: 1687-5826
    Electronic ISSN: 1687-5834
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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