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Ultra-Compact Metamaterial Absorber with Low-Permittivity Dielectric Substrate

Ultra-Compact Metamaterial Absorber with Low-Permittivity Dielectric Substrate

We first add meander lines within the resonators while keep the outer ring size fixed to decrease the operating frequency of the MA (equivalent to reduce the electric size for a given frequency). The meander lines technique has been widely used in the engineer area for reducing the electric size of antennas or microwave circuit components, as well as reducing the electric size of metamaterial units [32, 33]. Here we gradually add the meander lines to see the decreases of the absorbing frequency. As shown in Fig. 2(a), there are maximum seven obtainable meander lines for our chosen resonator with the line width of 0.1 mm and space of 0.1 mm between two lines. Therefore, we modeled all the conditions with different orders of meander lines and show the result in Fig. 2(b). It is seen that, with the increase of meander line orders, the absorbing frequency red-shifts gradually, and the absorption strength is also reduced. This is because with additional meander line orders, the equivalent electric length and thus the self-inductor of the resonator increase. Therefore, the resonance frequency decreases rapidly. At the same time, the equivalent impedance [27] of the MA also changes to inductive domain, and the MA becomes impedance mismatch to the background space. It should be noted that before we get the final MA size, we do not focus on the impedance match because it is easy to be realized by changing the substrate thickness which will be performed later.
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A PIN-Loaded Microstrip Patch Antenna with the Ability to Suppress Surface Wave Excitation

A PIN-Loaded Microstrip Patch Antenna with the Ability to Suppress Surface Wave Excitation

Abstract—A circular microstrip patch antenna design is proposed for applications that require suppression of surface waves and lateral waves. The proposed design is composed of a circular patch loaded with a single shorting pin on a grounded inhomogeneous dielectric substrate with a desired effective permittivity. The modal equation for the normalized resonance frequency of this design is solved numerically. Simulated and measured radiation patterns show that a good reduction of surface waves and lateral waves is achieved. A comparison between the present work and an alternative design in the literature is presented in this paper. The proposed design could find applications in large patch antenna arrays where mutual coupling needs to be eliminated and in high-precision global positioning system receivers where multipath interfering signals associated with low-angle reflection affect position accuracy.
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Material-Loaded High Q-Factor Slot Resonator and Measurement of Relative Permittivity

Material-Loaded High Q-Factor Slot Resonator and Measurement of Relative Permittivity

The geometric configuration of the proposed ground plane slot resonator is shown in Fig. 1. The structure consists of a 50 Ω microstrip line on the top layer and a rectangular slot is etched in the ground plane of substrate. Two metallic plates forming a parallel plate capacitor is soldered with the ground plane across the ground slot. The low loss dielectric material could be placed between two metallic plates to increase the loading capacitance. The maximum electric field in the slot is at the centre of the slot; where parallel plates are soldered.

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Dielectric Slab Mode Antenna for Integrated Millimeter wave Transceiver Front ends

Dielectric Slab Mode Antenna for Integrated Millimeter wave Transceiver Front ends

A simple planar dielectric lens on top of the grounded slab guide is capable of collimating the beam in the horizontal plane. This effect can be explained by a local increase in the substrate thickness, which in turn decreases the phase velocity of the guided wave in those zones. The cylindrical phase fronts of the launched surface wave are flattened in this way to augment the antenna gain. A simple but efficient method being available to determine the phase constant in a layered slab guide is the transverse resonance technique [12,13]. Its distinct advantage is that boundary conditions at dielectric interfaces can easily be handled as junctions of different transmission lines. The phase constants β of the guided modes are obtained by finding the roots of a single characteristic equation. Figure 4 shows the cross-section of the grounded slab guide including a low-permittivity insulation film. Its transverse resonance representation is shown on the right hand side.
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Effect of local A site strain on dipole stability in A6GaNb9O30 (A = Ba, Sr, Ca) tetragonal tungsten bronze relaxor dielectrics

Effect of local A site strain on dipole stability in A6GaNb9O30 (A = Ba, Sr, Ca) tetragonal tungsten bronze relaxor dielectrics

display relaxor behaviour in their dielectric response, i.e., a fre- quency dispersion in both the real and imaginary components of the complex permittivity. We observed that in these materials the dipole stability (characterised by the temperature of the peak in the permittivity) increases as the size of the M 3+ Fig. 1 (Colour online). (a) Polyhedral representation of the aristotype P 4/ mbm tetragonal tungsten bronze (TTB) structure viewed down the c -axis (B1 octahedra are shown in light green, B2 octahedra in dark blue, with A1 and A2 cations represented by dark red and light green spheres, respectively); (b) pseudo-ternary phase diagram showing region of single phase TTB compositions in Ba 6−x−y Sr x Ca y GaNb 9 O 30 .
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Measurable Dielectric Permittivity Range for TE and TM Modes in a Shielded Dielectric Resonator

Measurable Dielectric Permittivity Range for TE and TM Modes in a Shielded Dielectric Resonator

In this paper we presented a general methodology which may be useful to determine the usable dielectric range for material characterization. Due to the presence of the central cylinder, a displacement of the resonant fre- quency occurs proportional to the permittivity constant of the material until the resonant pattern of the mode under study can no longer exist. It means that for a given cavity and fixed rod’s radius to be located at the center of the cavity there exists a maximum value of measurable permittivity constant. No resonant conditions can be satisfied for higher permittivity values. The best alternative in order to increase the range of permittivity constant that can be measured reducing the radius of the central dielectric rod or choosing a higher resonant mode with the disadvantage that cavity loses can affect the results by changing the resonant frequency and the quality factor. We have shown that the behavior of the resonant frequency versus the dielectric constant should be taken into account when selecting the best appropriate region with high sensitivity in order to ensure the repeatability of measurement and to reduce the uncertainty associated to the measurement. Finally we have shown with a simple example the electromagnetic characterization of heavy oil with 11 API selecting a proper radious for a petroleum holder made of quartz of purity 99%.
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DESIGN OF COMPACT ASYMMETRIC COPLANAR STRIP FED ANTENNAS FOR WLAN APPLICATIONS

DESIGN OF COMPACT ASYMMETRIC COPLANAR STRIP FED ANTENNAS FOR WLAN APPLICATIONS

Now days, this world is based on technology. The new research & development of wireless communication systems has the main region of this changed era. To fulfill the demand of these, invention of compact microstrip antennas with high gain and wideband operating frequencies has developed. Microstrip patch antenna has many salient features like small size, low profile, light weight, simple realization process and low manufacturing cost. With so many advantages, MSPA have some disadvantages also, such as narrow bandwidth etc. To improve the performance & Enhancement of the performance of such antennas &to meet the demand of bandwidth is necessary [1]. There are many ways via them, we can improve the bandwidth of antennas, including of the substrate material, via different ways with low dielectric substrate, slotted patch antenna, the use of various impedance matching and feeding techniques, with the use of absorbers & resonators [2-8].
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Structure and dielectric properties of sol gel processed Ba (Fe1/2Nb1/2) O3 ceramics

Structure and dielectric properties of sol gel processed Ba (Fe1/2Nb1/2) O3 ceramics

The samples were subsequently calcined at various temperatures from 600°C to 900°C for 8 hours. The progress of the reaction was followed with the help of an X-ray diffractometer (XRD) with CuKα (λ=1.5405Å) radiation. For dielectric measurements, the powder samples were pressed into pellets with a uniaxial pressure of 8 tons/cm 2 , and then sintered at 1100°C for 8 h, with a heating rate of 5°C/min. The microstructure of the ceramics was examined by scanning electron microscopy (SEM) (Quanta 200 FEI model EDAX).

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Kinetic features of the oxidation of secondary alcohol by polymer   supported chromic acid

Kinetic features of the oxidation of secondary alcohol by polymer supported chromic acid

The oxidation of secondary alcohol was investigated to compare the polymer substrate supported reagent with a commercially available cross-linked polymeric reagent. The reagent supported on anion exchange resin was found to be more efficient in the oxidation reaction. The reagent is very easily separated from the reaction mixture and can be manually removed from the reaction mixture, which remains clear during and after the reaction. The kinetics of oxidation of secondary alcohol with chromic acid supported on anion exchange resins like Duolite A-101[Cl - ] and Ambersep 900[ OH ] in 1,4-dioxane has been studied. The reaction is found to be of zero order each in concentration of alcohol and oxidant. The stoichiometric coefficient of the reaction has been found to be 2:1. The oxidation products have been isolated and characterized by their derivatives, UV and FT-IR spectral studies. The effect of substituent’s on the rate of oxidation and activation parameters for the overall reactions has been computed from Arrhenius plot.
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Study of Effective Dielectric Permittivity and Capacitance for Finite Dielectric Thickness Coplanar Waveguide

Study of Effective Dielectric Permittivity and Capacitance for Finite Dielectric Thickness Coplanar Waveguide

Fig. 4 (a) & (b) shows 2D & 3D model for FCPW respectively obtained through SONNET software simulation [17]. Simulation is done on Alumina and Roggers substrate with εr =9.8, loss tangent tanδ = 0.0002 and εr =6.0, loss tangent tanδ = 0.0023 respectively. The simulated parametric study results and conformal mapping analysis for FCPW are obtained. Graph shown below represents the effect of aspect ratio and gap between strip and ground plane on capacitance, Effective dielectric permittivity, transmission coefficient and reflection coefficient for varying height of substrates.
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Numerical and Experimental Analysis of Wideband E-Shape Patch Textile Antenna

Numerical and Experimental Analysis of Wideband E-Shape Patch Textile Antenna

In order to design a patch textile antenna, a selection of suitable conducting and non-conducting textile materials is required. Conducting material is applied to both the patch and the ground plane, while non-conducting textile is needed for the antenna substrate layer. For the antenna substrate, a fleece fabric is chosen because of its high thickness and a low permittivity of 1.14, which are excellent properties for textile antenna design. The three fleece fabric layers are stitched together in order to ensure a well-defined substrate thickness and to keep the antenna conformal when it is bent, which has a thickness of 10 mm and provides an adequate antenna bandwidth. The conducting material is self-adhesive copper foil tape from Shenzhen JUNYE Inc., which has a thickness of 0.035 mm and provides low surface resistivity Rs < 0.03 Ω/sq. The self-adhesive side makes it easy to fasten the copper tape to the substrate. This conducting material is chosen also because of its easy handling such as cutting and sewing.
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PREPARATION AND CHARACTERIZATION OF NANOCRYSTALLINE Ba(Ti0.96SnxZr0.04-x)O3 CERAMIC

PREPARATION AND CHARACTERIZATION OF NANOCRYSTALLINE Ba(Ti0.96SnxZr0.04-x)O3 CERAMIC

2003; Lu et al., 2004; Wei et al., 2007) It is known that the cubic- tetragonal phase transition displays a continuous crossover with increase in the content of Sn from a sharp ferroelectric phase transition to a diffused phase transition and towards a relaxor-type behavior. On the other hand, the Zr addition in BZT lowers the dielectric loss due to its larger ionic size which expands the perovskite lattice whereas increase in its concentration induces a reduction in the average grain size, decreases the dielectric permittivity (𝜀 𝑟 ) enabling it to maintain a low and stable leakage current (Rehrig et al., 1999; Zhi et al., 2000 and 2001). The Curie temperature of barium titanate system can be altered by the substitution of dopants into either A- or B-site. Partial replacement of titanium by tin, zirconium, or hafnium generally leads to a reduction in Tc and an increase in the permittivity maximum (𝜀 𝑚𝑎𝑥 ) with dopant content (Hennings et al., 1982). Therefore, co-
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Left-Handed Materials Based on Crystal Lattice Vibration

Left-Handed Materials Based on Crystal Lattice Vibration

As expected from Mie theory, the dielectric sphere is equivalent to a magnetic dipole near the magnetic resonance mode and the magnetic field is mainly localized in the sphere as shown in Figure 4(a). However, when the CTO rods are placed beside the dielectric sphere, the magnetic field distribution is changed. The magnetic field in the gap enhances greatly while that in the sphere decreases as the rod approaches the dielectric sphere. When the distance between the rod and the sphere is reduced to zero, the intensity of the magnetic resonance even decreases by about 15% from about 5.7×10 4 A/m to
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Dielectric permittivity modulation of liquid crystals for microwave applications

Dielectric permittivity modulation of liquid crystals for microwave applications

Figure 5 Dielectric tunability T (%, 3GHz) vs ∆n/ne (%, 589nm) for tested LCs. The fairly high correlation coefficients (for 3GHz and 30GHz) indicated in Figure 4 mean that, for variety of LCs, the dielectric anisotropy at microwave regime is correlated quite well with the birefringence in visible (589nm). This finding is indirectly supported by another research work in the MMW regime (Nose et al [4]). They discovered that there was strong correlation between the refractive indices for MMW and for the visible wavelengths. Both the results of dielectric anisotropy (by us) and birefringence (by Nose et al [4]) confirm there is a correlation between the dielectric /optical properties in MMW and visible regions. This behavior is not only interesting but also useful. It means that, to obtain a certain dielectric modulation ∆ε in MMW regime, we can select a LC material according to its birefringence value at optical frequencies.
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Uncertainty Minimization in Permittivity Measurements in Shielded Dielectric Resonators

Uncertainty Minimization in Permittivity Measurements in Shielded Dielectric Resonators

Continuing with our previous work [1] in this paper, we present an effective method that minimizes the uncertainty in the measurement of the real dielectric permittivity of a material. As we indicated previously, the method is valid only for low loss materials in view of the nature of the exact relations between permittivity, sample and cavity dimensions, measured resonant frequency and the unloaded Q- factor for the resonant structures. Resonant methods are the preferred technique in dielectric permittivity measurements over non-resonant measurements [2], in view to their higher accuracy and sensitivity. Although, recent papers have discussed the problems associated to the estimation of uncertainty in the measurement of dielectric permittivity of materials, but only a few have proposed a systematic methodology for the reduction of the uncertainty associated to the measurement of the dielectric permittivity using resonant cavities [3].
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Radar Scatter from Layered Media and Rough Surfaces

Radar Scatter from Layered Media and Rough Surfaces

It is apparent from the salinity profile of Figure 6 that there are three distinct regions. For the first two metres of the ridge, the salinity has a mid-level average value with high variability. From 2 to 3 m the average salinity is low with low variability and the remainder of the ridge has high salinity that is highly variable. At first glance it appears that these three layers correspond to the sail, consolidated layer and rubble, as illustrated in Figure 4, however, the authors do not provide information on the consolidated layer. One additional link between the physical model and the ice properties can be observed from the brine volume plot. Brine volume, which is a calculated quantity, exhibits the same three layers plus an extra layer at the bottom of the ridge where the value rapidly increases. The final layer likely corresponds to the skeletal layer at the ridge bottom. The skeletal layer is a lattice of weak ice a few centimeters thick that undergoes advective transfer with the sea water.
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Optical, dielectric and magnetic properties of

Optical, dielectric and magnetic properties of

effect of Nd 3+ doping on the dielectric permittivity and magnetization in the wide frequency range.. 21.[r]

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Dielectric Behaviour of Pure and Dye Doped Nematic Liquid Crystal BKS/B07

Dielectric Behaviour of Pure and Dye Doped Nematic Liquid Crystal BKS/B07

The dielectric parameters  and  have been meas- ured for a nematic liquid crystal BKS/B07 in the fre- quency range of 1 kHz to 10MHz for the temperature range of 70˚C to 135˚C. Figure 3 and Figure 4 represent typical frequency dependence spectra of the real and imaginary part of the dielectric permittivity measured for nematic sample BKS/B07 and dye doped mixtures 1 and 2. The dielectric permittivity is found to be either con- stant or to decrease as the frequency increases [17-22] for pure sample. Lower values of  at higher frequency suggest that the molecules rotate about their long mo- lecular axis [23]. The behaviour of  for the dye based mixtures 1 and 2 is similar to that of pure sample but the values of dielectric constants are higher in comparison to the corresponding values of pure sample.
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Effective Permittivity Tensor for a Metal-Dielectric Superlattice

Effective Permittivity Tensor for a Metal-Dielectric Superlattice

[see triangles therein]. Evidently, the predictions of the formula (17) (solid line, labeled with number 1 in Fig. 1) coincide with the numerical results. Notice that ε x (ω) has a zero at ω = ω 1 ≈ 0.121ω P , which indicates the top or width of the low-frequency band gap (0 < ω < ω 1 ) in the photonic band structure for modes propagating along the growth direction of the metal-dielectric superlattice (Fig. 2). Interestingly, the dispersion relation k(ω) = (ω/c) p ε x /ε 0 , calculated with the effective

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An Elliptical Ring FSS Antenna excited with Microstrip Feed for Satellite Application

An Elliptical Ring FSS Antenna excited with Microstrip Feed for Satellite Application

The proposed design is a periodic array of elliptical ring with interconnections. The dimension of proposed antenna is 150mm×150mm. The substrate used is FR4 epoxy with relative permittivity 4.4, relative permeability 1, dielectric loss tangent 0.02 and magnetic loss tangent 0.The height of the substrate is 1.6mm.Ground lies below substrate which is of negligible thickness. Above the substrate patches are designed. The antenna design consist of 3×4 array. It consist of 12 periodic elliptical ring patches. Elliptical ring consist of two ellipses, one outer ellipse and one inner ellipse. The desired design of the patch is obtained by subtracting one ellipse from another. The outer ellipse has a major radius of 10mm and ratio is 2.The inner ellipse has a major radius of
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