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103 results on '"Ghosh, Bratin"'

1. Directivity Enhancement and Excitation of Space Wave, Leaky Wave, and Creeping Waves for a PEC Cylinder Coated With a Uniaxial Dielectric

Author

Singh, Mahesh, Ghosh, Bratin, and Sarabandi, Kamal

Abstract

Directivity enhancement for a conducting cylinder coated with a uniaxial dielectric layer and excited with an electric current source is investigated. A detailed investigation is conducted for all source polarizations. A distinct contribution of the current work relative to the literature is the realization of extremely high directivity corresponding to space- and leaky-wave radiations for cylindrical structures. The computed space- and leaky-wave radiation patterns are compared with simulations using two simulation tools. The creeping-wave characteristics for the configuration are also investigated.

Published
2024
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2. Analysis of Input Impedance and Radiation Characteristics of a Dipole Embedded in and Near a Stratified Uniaxial Sphere

Author

Shaikh, Tazeen, Ghosh, Bratin, and Sarabandi, Kamal

Abstract

In this work, the Green’s function for a dipole in a stratified uniaxial anisotropic spherical configuration is evaluated, with the dipole in the anisotropic layer. The particular part of the Green’s function is computed by matching the electromagnetic fields at the source in the anisotropic layer. The homogeneous part of the Green’s functions is found by imposing boundary conditions at the anisotropic and isotropic layer interfaces. The source-free resonant frequencies of the transverse electric (TE) and transverse magnetic (TM) modes for the antenna configuration are also evaluated. The input impedance and fields radiated by the dipole in the multilayer anisotropic sphere are computed. The technique is also used for the evaluation of the Green’s function, input impedance, and radiated fields for a dipole located in the vicinity of the stratified uniaxial anisotropic sphere. The variation of input impedance, reflection coefficient, and excited modes with change in anisotropy is thoroughly investigated for both the antenna configurations. The excited modes in both the configurations are also characterized in terms of their quality factor, bandwidth, gain, and radiation efficiency. The radiation characteristics with change in anisotropy are also evaluated.

Published
2023
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18. Coplanar waveguide feed to the hemispherical DRA

Author

Ghosh, Bratin, Ghosh, Kunal, and Panda, Chandra Sekhar

Subjects
Waveguides -- Design and construction, Dielectric resonators -- Usage, Business, Computers, Electronics, Electronics and electrical industries
Abstract

In this communication, several coplanar waveguide topologies to the hemispherical DRA are presented. It is seen that the inductive and the circular-loop CPW feed configurations offer the flexibility to excite the fundamental [TE.sub.111] resonant mode of the hemispherical DRA close to the source free resonant frequency, due to the presence of metallization in the coupling region. Dual-band behavior is observed with the capacitive feed due to the DRA and slot resonant modes, which are displaced with respect to the unperturbed modes due to the uninterrupted slot. The radiation characteristics of the antenna are also explained. Index Terms--Capacitive, coplanar waveguide (CPW), circular-loop, dielectric resonator, inductive.

Published
2009

21. TLM-based modal-extraction approach for the investigation of siscontinuities in the rectangular waveguide and the NRD

Author

Ghosh, Bratin, Simons, Neil R.S., Shafai, Lotfollah, Ittipiboon, Apisak, and Petosa, Aldo

Subjects
Microwave circuits -- Analysis, Waveguides -- Analysis, Strip transmission lines -- Usage, Business, Computers, Electronics, Electronics and electrical industries
Abstract

This paper describes the development of a rigorous transmission-line matrix-based modal-extraction approach to analyze discontinuities in guided-wave structures in general, with particular attention to the nonradiative dielectric waveguide (NRD). The motivation for this paper arose from the need to ascertain the admittance of a slot in the ground plane of an NRD without relying on experimental data. These data enabled one to design an NRD-based slot array following the methodology of Malherbe, Malherbe et al., and Ghosh et al.. Previous work in this area relied on placing observation points sufficiently remote from the discontinuity in order to ensure the decay of scattered evanescent modes to appreciably low levels. The method discussed here obviates this requirement and allows the evaluation of generalized scattering-matrix coefficients arbitrarily close to the discontinuity, thus significantly reducing the computational overhead. Results pertaining to discontinuities in the NRD and the rectangular waveguide have been presented and shown to give good agreement with those in the literature and with measurements. The perfectly matched layer has been used as an absorbing boundary condition in our simulations. Finally, the results have been verified using the power-conservation and Poynting's theorems. Index Terms--Discontinuities, modal extraction, NRD, PML, TLM.

Published
2002

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