Two-dimensional microwave band-gap structures of different dielectric materials
TL;DR: In this paper, the use of low dielectric constant materials to form two-dimensional microwave band-gap structures for achieving high gap-to-midgap ratio was reported.
Abstract: We report the use of low dielectric constant materials to form two-dimensional microwave band-gap structures for achieving high gap-to-midgap ratio. The variable parameters chosen are the lattice spacing and the geometric structure. The selected geometries are square and triangular and the materials chosen are PTFE (e = 2.1), PVC (e = 2.38) and glass (e = 5.5). Using the plane-wave expansion method, proper lattice spacing is selected for each structure and material. The observed experimental results are analyzed with the help of the theoretical prediction
Citations
More filters
TL;DR: In this article, an experimental verification of the sensitivity improvement of evanescent-field probes using single-negative (SNG) metamaterials is presented, and the deviation in the phase of reflection coefficient due to the target is measured.
Abstract: In this paper, we present experimental verification of the sensitivity improvement of evanescent-field probes using single-negative (SNG) metamaterials. Artificial magnetic materials are designed and fabricated to realize a ?-negative SNG material. The response of an electrically small probe to an electrically small target is investigated numerically and experimentally. The deviation in the phase of reflection coefficient due to the target is measured. When an SNG layer is employed, phase shift due to the presence of a target is improved nine times compared to a probe without an SNG layer.
13 citations
TL;DR: In this article, a single-stage power amplifier and two-way Doherty amplifier are linearized by the technique that uses second harmonics and fourth-order nonlinear signals.
Abstract: In this article, a single-stage power amplifier and two-way Doherty amplifier are linearized by the technique that uses second harmonics and fourth-order nonlinear signals. Measurements of the linearization effects on the third- and fifth-order intermodulation products have been carried out. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:425–430, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27294
12 citations
Patent•
28 Oct 2009
TL;DR: In this paper, the authors propose a sandwich vehicle structure that allows for the confined propagation of electromagnetic radiation within the sandwich vehicle, where the core is composed of a core medium and a plurality of spaced apart core members embedded in the core medium.
Abstract: A sandwich vehicle structure may allow for confined propagation of electromagnetic radiation within the sandwich vehicle structure. The sandwich vehicle structure may include at least one upper conducting plate, at least one lower conducting plate, and a core extending between the upper and lower conducting plates. The core may comprise a core medium, and a plurality of spaced apart core members embedded in the core medium and extending between the upper and lower conducting plates. The core medium and the core members may allow for the propagation of electromagnetic radiation within the core.
10 citations
TL;DR: In this article, the optical properties of a one-dimensional (1D) photonic heterostructure with graded-index nonlinear materials are analyzed theoretically and the influence of the gradation profile of the nonlinear layers on the linear and nonlinear responses of the structure is analyzed.
Abstract: The optical properties of a one-dimensional (1D) photonic heterostructure with graded-index nonlinear materials are demonstrated theoretically. The influence of the gradation profile of the graded-index nonlinear layers on the linear and nonlinear responses of the structure are analysed. It is shown that the Q-factor of the defect mode and the threshold input intensity to achieve the optical bistability in the used photonic heterostructure depend on the gradation profile of the graded-index nonlinear layers.
4 citations
Dissertation•
25 Aug 2009
TL;DR: In this paper, the effect of placing DNG and SNG layers between the near field probes and the targets is investigated theoretically, and it is shown using quantitative measures that the sensitivity can be increased using double negative and single negative (SNG) materials for a target in vacuum and for a buried target.
Abstract: In the last decade, design and application of negative materials have been one of the most interesting subjects in the electromagnetic research. The extraordinary properties of double negative (DNG) and single negative (SNG) materials have been studied extensively over this period. In this thesis, one of the unusual properties of negative materials, the evanescent amplification, is used to improve the sensitivity of the near field probes. The effect of placing DNG and SNG layers between the near field probes and the targets are investigated theoretically. A sensitivity definition is introduced for evanescent probes and it is shown using quantitative measures that the sensitivity can be increased using DNG and SNG materials for a target in vacuum and for a buried target. The electromagnetic loss of the negative materials and the mismatch between the material properties of the host medium and DNG and SNG materials are studied. Using an unmatched DNG layer or SNG layer enhances the sensitivity within an evanescent spectrum range while a lossless and matched DNG layer improves the sensitivity of entire evanescent spectrum. The idea of using negative materials is implemented over conventional near field probes by numerical experiments. Sensitivities of open-ended waveguides and open-ended coaxial lines for a specific application are studied in the presence of negative materials. In the case of precursor pitting detection on airplane bodies, the sensitivity of an open-ended waveguide probe is increased by 35 times for a λ/10 sized cubic crack. It is also shown that the negative material increases the quality of the image generated by the probe. The sensitivity improvement is also verified for an open-ended coaxial line. A 11 times improvement is achieved for a similar detection practice, with a λ/20 sized crack. The effect of coaxial line size and the dielectric material on the sensitivity enhancement are studied. The improvement is studied theoretically and numerically for an electrically small dipole. Theoretical studies show that when a small dipole is placed within a spherical shell made of DNG materials, the antenna parameters of the dipole becomes more sensitive to the position of a target placed outside the negative material shell. The field distribution generated by a small dipole in a multilayered spherical medium is studied for this purpose. Numerical analysis of a small dipole placed next to a planar DNG layer is presented. The DNG layer increases the sensitivity of the dipole due to a λ/30 sized metallic target by 5.5 times. To provide experimental verification, the sensitivity of an electrically small loop is studied. SNG materials with a negative permeability around 1.25 GHz are designed
1 citations
References
More filters
TL;DR: In this paper, a two-dimensional periodic dielectric structure that has a complete inplane photonic band gap for both polarizations was identified, and a triangular lattice of air columns was found to have the desired band gap properties.
Abstract: A systematic theoretical investigation is undertaken in order to identify a two‐dimensional periodic dielectric structure that has a complete in‐plane photonic band gap for both polarizations. Of the various structures studied, only a triangular lattice of air columns is found to have the desired band‐gap properties. Microwave transmission experiments are performed to test the theoretical predictions.
330 citations
TL;DR: The photonic band strucfure in a two-dimensional dielectric array is investigated using the coherent microwave transient spectroscopy (COMITS) technique and the experimental results are compared with theoretical predictions obtained using the plane-wave expansion technique.
Abstract: The photonic band structure in a two-dimensional dielectric array is investigated using the coherent microwave transient spectroscopy (COMITS) technique. The array consists of alumina-ceramic rods arranged in a regular square lattice. The dispersion relation for electromagnetic waves in this photonic crystal is determined directly using the phase sensitivity of COMITS. The experimental results are compared to theoretical predictions obtained using the plane-wave expansion technique. Configurations with the electric field parallel and perpendicular to the axis of the rods are investigated.
304 citations
TL;DR: It is concluded that studies of this model scattering system allow the quantitative evaluation and testing of ideas regarding wave propagation and localization in strongly scattering media.
Abstract: We have calculated and measured the properties of X-band microwaves propagating in a 2D array of low-loss high-dielectric-constant cylinders. Transmission bands and photonic band gaps are conclusively identified in excellent agreement with the theoretical predictions. Detailed data on the properties of isolated defect states are also presented. We conclude that studies of this model scattering system allow the quantitative evaluation and testing of ideas regarding wave propagation and localization in strongly scattering media.
239 citations
TL;DR: In this article, the photonic band gap was introduced, a frequency band in three-dimensional dielectric structures in which electromagnetic waves are forbidden, irrespective of propagation direction in space.
Abstract: The analogy between electromagnetic wave propagation in multidimensionally periodic structures and electron wave propagation in real crystals has proven to be a very fruitful one Initial efforts were motivated by the prospect of a photonic band gap, a frequency band in three-dimensional dielectric structures in which electromagnetic waves are forbidden, irrespective of propagation direction in space Today many new ideas and applications are being pursued in two and three dimensions, and in metallic, dielectric and acoustic structures, etc The author reviews the early motivations for this work, which were derived from the need for a photonic band gap in quantum optics This led to a series of experimental and theoretical searches for the elusive photonic band-gap structures, those three-dimensionally periodic dielectric structures which are to photon waves what semiconductor crystals are to electron waves Then he describes how the photonic semiconductor can be 'doped', producing tiny electromagnetic cavities Finally he summarizes some of the anticipated implications of photonic band structure for quantum electronics and the prospects for the creation of photonic crystals in the optical domain
223 citations
TL;DR: In this paper, the photonic band structure for electromagnetic waves in a structure that consists of a periodic array of parallel dielectric rods of circular cross section, whose intersections with a perpendicular plane constitute a square lattice.
165 citations