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  • Articles  (62)
  • Hindawi  (62)
  • American Meteorological Society
  • Blackwell Publishing Ltd
  • Copernicus
  • National Research Council Canada (NRC)
  • 2020-2022
  • 2010-2014  (62)
  • 1960-1964
  • 2012  (62)
  • 1964
  • International Journal of Microwave Science and Technology  (39)
  • 29424
  • 84647
  • Electrical Engineering, Measurement and Control Technology  (62)
  • Mathematics
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Collection
  • Articles  (62)
Source
Publisher
  • Hindawi  (62)
  • American Meteorological Society
  • Blackwell Publishing Ltd
  • Copernicus
  • National Research Council Canada (NRC)
    • +
Years
  • 2020-2022
  • 2010-2014  (62)
  • 1960-1964
Year
Journal
Topic
  • Electrical Engineering, Measurement and Control Technology  (62)
  • Mathematics
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
  • 1
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    A Systemic Approach to the Compensation of Rain Attenuation in Ka-Band Communication Satellites (2012)
    Hindawi
    Details
    Publication Date: 2012-12-05
    Description: Rain attenuation at Ka-band is a severe phenomenon that drastically impairs satellite communications at these frequencies. Several adaptive compensation techniques have been elaborated to counteract its effects and most often applied one at a time. The present paper proposes the contemporary exploitation of different techniques in a combined approach. Such an integrated approach is thoroughly analyzed in a simplified scenario and will be shown to achieve a very effective solution, making the Ka-band spectrum fully available for broadband satellite applications and network-centric systems.
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    Electronic ISSN: 1687-5834
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  • 2
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    Performance Comparison of UWB Pulse Modulation Schemes under White Gaussian Noise Channels (2012)
    Hindawi
    Details
    Publication Date: 2012-10-03
    Description: In this paper, and for the first time, the performance of various ultra wideband pulse modulation schemes are discussed and compared in terms of narrowband interference robustness, symbol error rate, system complexity, data rate, and maximum transmit power with respect to transceiver distance and channel capacity. The channel model is the UWB IEEE 802.15.3a multipath indoor channel model under additive white Gaussian noise. The transmit power was evaluated by integrating the fifth derivative of the power spectrum density of the Gaussian pulse over the whole bandwidth.
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  • 3
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    A Novel Internal Dual-Polarized EBG Antenna for Indoor Reception of UHF Terrestrial Digital TV Broadcasting (2012)
    Hindawi
    Details
    Publication Date: 2012-08-31
    Description: A novel internal antenna has been developed for indoor reception of UHF terrestrial digital TV broadcasting. The overall size of some configurations of the new antenna is less than 2 cm3, and its weight is less than 1 gm. It is made of a flexible material that can be bent or folded and shaped in any form. It is an unbalanced resonant antenna that does not need a matching circuit. The new antenna can be fully embedded inside TV sets or portable computers. It has a bandwidth of about 68%. Thus, it can also cover the bands of GSM and CDMA, which is advantageous in case of portable computers. The new antenna is linearly polarized. It can be easily modified to be dual polarized by combining two orthogonal antennas with one or two feed points. The overall efficiency of some configurations of the new indoor digital TV receiving antenna is more than 80%, and its peak gain is about 2 dBi over the whole UHF band. The peak gain can be increased to more than 5 dBi by adding EBG (electromagnetic bandgap) structures. The EBG structure also increases the efficiency to around 90%.
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  • 4
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    Design and Realization of GaAs Digital Circuit for Mixed Signal MMIC Implementation in AESA Applications (2012)
    Hindawi
    Details
    Publication Date: 2012-06-21
    Description: A complete design flow starting from the technological process development up to the fabrication of digital circuits is presented. The aim of this work is to demonstrate the GaAs Enhancement/Depletion (E/D) double stop-etch technology implementation feasibility for digital applications, aimed at mixed signal circuit integration. On the basis of the characterization of small E/D devices with different Gate peripheries, developed by the SELEX-SI foundry, and the analysis of several GaAs-based logical families, the most suitable logic for the available technology has been selected. Then, simple test vehicles (level shifters, NOR logic gates and D Flip-Flops) have been designed, realized, and measured to validate the design strategy applied to the GaAs E/D process. These logical circuits are preliminary to the design of a more complex serial-to-parallel converter, to be implemented onto the same chip together with RF analog blocks, such as stepped attenuators and phase shifters.
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  • 5
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    High Q-Factor Wideband Resonators for Millimeter and Submillimeter Applications (2012)
    Hindawi
    Details
    Publication Date: 2012-06-21
    Description: Physical principles for designing a multipurpose set of high Q-factor quasioptical and corrugated resonators with automatic frequency tuning (Q>6×104, VSWR<1.6) that can operate in the frequency band from 37.5 to 400 GHz are presented. The electrodynamical calculation methods of resonators, the constructive particularities of resonators, the methods and results of the experimental researches are considered. This set of resonators can be used as a universal measuring resonator for measuring radio-signal fluctuations and parameters of different media, in particular, nanotube composites and high-temperature superconductors.
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  • 6
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    Fully Distributed Tunable Bandpass Filter Based on Ba0.5Sr0.5TiO3 Thin-Film Slow-Wave Structure (2012)
    Hindawi
    Details
    Publication Date: 2012-06-21
    Description: This paper presents simulation and measurement results of fully distributed tunable coplanar bandpass filters (BPFs) with center frequencies around 6 GHz that make use of ferroelectric Barium Strontium Titanate (BaxSr1−xTiO3 or BST-x) thin film as tunable material. The two experimental bandpass filters tested are based on a novel frequency-agile structure composed of cascaded half wavelength slow-wave resonators (2 poles) and three coupled interdigital capacitors (IDCs) optimized for bias voltage application. Devices with gap dimensions of 10 and 3 μm are designed and fabricated with a two-step process on polycrystalline Ba0.5Sr0.5TiO3 thin films deposited on alumina substrate. A frequency tunability of 9% is obtained for the 10 μm gap structure at ±30 V with 7 dB insertion loss (the BST dielectric tunability being 26% with 0.04 loss tangent for this gap size). When the structure gap is reduced to 3 μm the center frequency shifts with a constant 9 dB insertion loss from 6.95 GHz at 0 V to 9.05 GHz at ±30 V, thus yielding a filter tunability of 30% (the BST dielectric tunability being 60% with 0.04 loss tangent for this gap size), a performance comparable to some extent to localized or lumped element BPFs operating at microwave frequency (>2 GHz).
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  • 7
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    Time Reversal in Subwavelength-Scaled Resonant Media: Beating the Diffraction Limit (2012)
    Hindawi
    Details
    Publication Date: 2012-06-21
    Description: Time reversal is a physical concept that can focus waves both spatially and temporally regardless of the complexity of the propagation medium. Time reversal mirrors have been demonstrated first in acoustics, then with electromagnetic waves, and are being intensively studied in many fields ranging from underwater communications to sensing. In this paper, we will review the principles of time reversal and in particular its ability to focus waves in complex media. We will show that this focusing effect depends on the complexity of the propagation medium rather than on the time reversal mirror itself. A modal approach will be utilized to explain the physical mechanism underlying the concept. A particular focus will be given on the possibility to break the diffraction barrier from the far field using time reversal. We will show that finite size media made out of coupled subwavelength resonators support modes which can radiate efficiently in the far field spatial information of the near field of a source. We will show through various examples that such a process, due to reversibility, permits to beat the diffraction limit using far field time reversal, and especially that this result occurs owing to the broadband inherent nature of time reversal.
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  • 8
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    Fracture Toughness of Vinyl Ester Composites Reinforced with Sawdust and Postcured in Microwaves (2012)
    Hindawi
    Details
    Publication Date: 2012-09-14
    Description: A commercial vinyl ester resin supplied by Hetron Chemical Pty. was reinforced with varying percentages by weight of sawdust. The sawdust particles were sieved into 3 different sizes, which were
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  • 9
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    Analysis and Design of Ultra-Wideband 3-Way Bagley Power Divider Using Tapered Lines Transformers (2012)
    Hindawi
    Details
    Publication Date: 2012-06-21
    Description: An ultra-wideband (UWB) modified 3-way Bagley polygon power divider (BPD) that operates over a frequency range of 2–16 GHz is presented. To achieve the UWB operation, the conventional quarter-wave transformers in the BPD are substituted by two tapered line transformers. For verification purposes, the proposed divider is simulated, fabricated, and measured. The agreement between the full-wave simulation results and the measurement ones validates the design procedure.
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  • 10
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    The Effect of Bulk Density on Emission Behavior of Soil at Microwave Frequencies (2012)
    Hindawi
    Details
    Publication Date: 2012-06-21
    Description: Dielectric constant and dielectric loss (ε′ and ε″) of different soil samples with bulk densities varying from 1.3 to 2.0 gm/cm3 are determined at a single microwave frequency 9.78 GHz and at temperature 37.0°C. Different bulk densities of same soil are achieved by filling the wave guide cell with an equal volume but a different mass of soil. Further, ε′ and ε″ of these soil samples are also estimated by semiempirical model and compared with the experimental results. The values of ε′ and ε″ increase as bulk density of the soil increases. In view of microwave remote sensing, the Fresnel reflectivity of soil is computed from the knowledge of the complex dielectric constant and the surface boundary condition. Using Kirchhoff’s reciprocity theorem the microwave emissivity is estimated from Fresnel reflectivity of the surface. It is observed that the microwave emission from the soil surface inhibits as bulk density of soil increases. Further, the roughness of soil surface has been taken into consideration in the emissivity computation and observed that the emissivity increases with increasing roughness of the soil surface.
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