Multipole Theory Analysis of Cutoff Wavenumbers of Waveguides Partially Filled with Dielectric

A new approach, the multipole theory (MT) method, is presented for the computation of cutoff wavenumbers of waveguides partially filled with dielectric. The MT formulation of the eigenvalue problem of an inhomogeneous waveguide is derived. Representative computational examples, including dielectric-rod-loaded rectangular and double-ridged waveguides, are given to validate the theory, and to demonstrate the degree of its efficiency

A Simple Free-Space Method for Measuring the Complex Permittivity of Single and Compound Dielectric Materials

A simple and efficient method for determining the complex permittivity of dielectric materials from both reflected and transmitted signals is presented. It is also novel because the technique is implemented using two pyramidal horns without any focusing mechanisms. The dielectric constant of a noninteractive and distributive (NID) mixture of dielectrics is also determined

Excitation of low-profile equilateral-triangular dielectric resonator antenna using a conducting conformal strip

A new configuration that employs a conducting conformal strip to excite the low-profile equilaterial-triangular dielectric resonator antenna (DRA) of very high permittivity is proposed. As compared with the previous aperture-coupling configuration, the new configuration has a wider impedance bandwidth (- 5.5%) and a higher front-to-back radiation ratio. The return loss, radiation patterns, and antenna gain are measured and discussed

Enhanced Bandwidth Microstrip Patch Antennas Loaded with High Permittivity Dielectric Resonators

A novel technique fitr the bat dividth enhancement of conventional rectangular microstrip antenna is proposed in this paper. When a high permittivity dielectric resonator of suitable resonant frequency was loaded over the patch. the % bandwidth of the antenna was increased by more than five tunes without much affecting its gain and radiation performance. A much more improved bandwidth was obtained when the dielectric resonator was placed on the feedline. Experimental study shows a 2:1 VSWR bandwidth of more than 10% and excellent cross polarization performance with increased pass band and radiation coverage abnost the same as that of rectangular microstrip antenna

Power characteristics of dielectric optical piet hein waveguides

A fairly rigorous analytical treatment of the power characteristics of dielectric optical waveguides with Piet Hein core-cross sectional geometry is presented in this paper. This kind of wareguide structure would be advantageous owing to the absence of corners, which are found in rectangular guides, resulting in undesirable loss (hit to the scattering of light. In order to simplify this theoretical approach. em approximation of vanishing refractive index difference between the guiding and the non-guiding sections is implemented. The variation eJ logarithmic power is shown for different dimensions of the core, corresponding to different azimuthal modal indices. It is found that the nutlet with higher index values carry less logaritlunic power in the lower tail of the propagation 's constant range, and this feature affects the higher tail. A better kind of uniformity of the power distribution is observed near the higher tail of the range of propagation Constants

A compact very-high-permittivity dielectric-eye resonator antenna for multiband wireless applications

very-high-permittivity (e, = 100) multiband dielectrice> e resonator antenna is presented. The compact antenna, excited by a m:'crostrip line, resonates at two frequencies centered around the 1.9- GHz and 2.4-GHz bands with identical polarization . The behavior of the antenna at different positions along the feed line is studied and optimized. Multiple resonances with the same polarization and broad radioticn patterns suggest the suitability of the antenna for multiband wireless application

Low backscattered dual-polarised metallo-dielectric structure based on sierpinski carpet

A novel technique for backscattering reduction for both TE and TM polarisation, employing a metallo-dielectric structure based on Sierpinski carpet fractal geometry, is reported. A reduction in backscattered power of --30 dB is obtained for normal incidence in the X-band for the structure using the third iterated stage of the fractal geometry

Characteristics of a Microstrip-Excited High-Permittivity Tectangular Dielectric Resonator Antenna

The radiation characteristics of a microstrip-line-excited rectangular dielectric resonator antenna (DRA) are studied experimentally.The radiation charactristics and excitation of different modes are highly influenced by the orientation of the DR,feed line parameters ,and finite size of the ground plane

Wideband Oylindrioal Dielectric Resonator Antenna Excited Using an L-strip Feed

A broadband cylindrical dielectric resonator antenna (DRA) energized with an L-strip feed is presented The novel exciting technique achieves a 2:1 VSWR bandwidth of 18%. The variation of bandwidth for different feed parameters is also studied

T-strip-fed High-Permittivity Rectangular Dielectric Resonator Antenna for Broadband Applications

rectangular low-density, high-permittivity dielectric resona or antenna (DRA) excited by T-shaped microstrip feed offering a 2:1 VSWR bandwidth of -22% at 2.975 GHz is reported. The design methoaology and experimental results of the antenna are discussed. The excellent gain and radiation performance of the proposed antenna project: it as a potential candidate for telecommunication applications

L-strip-fed Wideband Rectangular Dielectric Resonator Antenna

In this paper, the advantages of using L-shaped microviij) feed to e.tcite a rectangular dielectric resonator cuuenna (DRA) by elemanagnetic coupling are presented. This feeding technique enhances the hardsvidth and gain of the antenna without affecting its size. The experimental re srdts are validated using Fidelity software based on the finitedifference tine-domain (FDTD) method

Rectangular Dielectric Resonator Antenna on a Conductor-backed Co-planar

In this paper, we present an effective excitation of a reelangular dielectric resonator antennas (DRA) with a conductor-hacked coplanar waveguide (CB-CPW). The radiation and resonance characteristics are found to van,, depending on the orientation of the DR on doe coplanar feed line. The effect of finite and infinite ground planes of CB-CPIV on the radiation characteristics of the rectangular DRA is studied. The orientation and position of the DR are optimized for maximum gain and bandwidth. The optimized antenna ,geometry offers --10.46 dBi gain and 7.5% bandwidth with low cross-polar radiation characteristics

Broadband Cylindrical Dielectric Resonator Antenna Excited by Modified Microstrip Line

The impedance bandwidth of a high permittivity cylindrical dielectric resonator antenna excited by a micro strip line was significantly improved by modifying the feed geometry. The 10 dB return loss bandwidth is enhanced from 12 to 26% without much affecting the gain and other radiation properties of the antenna. Good agreement has been observed between the predicted and measured results

Synthesis and Characterisation of Thermoplastic Ionomers based on Natural Rubber

Chemically modified novel thermo-reversible zinc sulphonated ionomers based on natural rubber (NR), radiation induced styrene grafted natural rubber (RI-SGNR), and chemically induced styrene grafted natural rubber (CI-SGNR) were synthesized using acetyl sulphate/zinc acetate reagent system. Evidence for the attachment of sulphonate groups has been furnished by FTIR spectra. which was supplanted by FTNMR results. Estimation of the zinc sulphonate group was done using spectroscopic techniques such as XRFS and ICPAES. The TGA results prove improvement in the therrno-oxidative stability of the modified natural rubber. Both DSC and DMTA studies show that the incorporation of the ionic groups affect the thermal transition of the base polymer. Retention of the improved physical properties of the novel ionomers even after three repeated cycles of mastication and molding at 120 degree C may be considered as the evidence for the reprocessabiJity of the ionomer. Effect of both particulate (carbon black. silica & zinc stearate) and fibrous fillers (nylon & glass) on the properties of the radiation induced styrene grafted natural rubber ionomer has been evaluated. Incorporation of HAF carbon black results in maximum improvement in physical properties. Silica reinforces the backbone chain and weakens the ionic associations. Zinc stearate plays the dual role of reinforcement and ptasticization. The nylon and glass filled lonorner compounds show good improvement in the physical properties in comparison with the neat ionomer. Dispersion and adhesion of the fillers in the ionomer matrix has been amply supported by their SEM micrographs. Microwave probing of the electrical behavior of the 26.5 ZnSRISGNR ionomer reveals that the maximum relative complex conductivity and the complex permittivity appear at the frequency of 2.6 GHz. The complex conductivity of the base polymer increases from 1.8x 10.12 S/cm to 3.3xlO·4 S/cm. Influence of fillers on the dielectric constant and conductivity of the new ionic thermoplastic elastomer has been studied. The ionomer I nylon compound shows the highest microwave conductivity. Use of the 26.5 ZnS-RISGNR ionomer as a compatibilizer for obtaining the technologically compatible blends from the immiscible SBR/NBR system has been verified. The heat fugitive ionic cross-linked natural rubber may be, therefore, useful as an alternative to vulcanized rubber and thermoplastic elastomer

Studies on Electrical and Thermal Properties of Certain Selected Photonic Materials

The present thesis is centered around the study of electrical and thermal properties of certain selected photonic materials.We have studied the electrical conduction mechanism in various phases of certain selected photonic materials and those associated with different phase transitions occurring in them. A phase transition leaves its own impressions on the key parameters like electrical conductivity and dielectric constant. However, the activation energy calculation reveals the dominant factor responsible for conduction process.PA measurements of thermal diffusivity in certain other important photonic materials are included in the remaining part of the research work presented in this thesis. PA technique is a promising tool for studying thermal diffusivities of solid samples in any form. Because of its crucial role and common occurrence in heat flow problems, the thermal diffusivity determination is often necessary and knowledge of thermal diffusivity can intum be used to calculate the thermal conductivity. Especially,knowledge of the thermal diffusivity of semiconductors is important due to its relation to the power dissipation problem in microelectronic and optoelectronic devices which limits their performances. More than that, the thermal properties, especially those of thin films are of growing interest in microelectronics and microsystems because of the heat removal problem involved in highly integrated devices. The prescribed chapter of the present theis demonstrates how direct measurement of thermal diffusivity can be carried out in thin films of interest in a simple and elegant manner using PA techniques. Although results of only representative measurements viz; thermal diffusivity values in Indium, Aluminium, Silver and CdS thin films are given here, evaluation of this quantity for any photonic and / electronic material can be carried out using this technique in a very simple and straight forward manner.