Basudeb Ghosh

Electromagnetic Transmission through Fractal Apertures in Infinite Conducting Screen

Fractals contain an infinite number of scaled copies of a starting geometry. Due to this fundamental property, they offer multiband characteristics and can be used for miniaturization of antenna structures. In this paper, electromagnetic transmission through fractal shaped apertures in an infinite conducting screen has been investigated for a number of fractal geometries like Sierpinski gasket, Sierpinski carpet, Koch curve, Hilbert Curve and Minkowski fractal. Equivalence principle and image theory are applied to obtain an operator equation in terms of equivalent surface magnetic current over the aperture surface. The operator equation is then solved using method of moments (MoM) with the aperture surface modeled using triangular patches. Numerical results are presented in terms of transmission coefficient and transmission cross-section for both parallel and perpendicular polarizations of incident plane wave which show the existence of multiple transmission bands.

RADIATION FROM CAVITY-BACKED FRACTAL APERTURE ANTENNAS

This paper investigates the properties of probe fed cavity- backed fractal aperture antennas. The problem is formulated using the flnite element-boundary integral (FE-BI) method in which the fleld inside the cavity is formulated using the flnite element method, and the mesh is truncated at cavity aperture surface using the boundary integral method. Several dual-band cavity-backed fractal aperture antennas based on Sierpinski gasket, Sierpinski carpet, plus shape fractal and Minkowski fractal are investigated. The numerical results obtained from the FE-BI code have been validated with simulations on HFSS.

Radiation From Rectangular Waveguide-Fed Fractal Apertures

We investigate the properties of fractal apertures fed by a rectangular waveguide. The self-similarity and space-filling properties of fractals have been exploited to achieve multi-band radiation. Some self-affine fractal geometries, suitable for waveguide-fed apertures, have been proposed and investigated. It is shown that the scale factor of the fractal geometry can be used as a design parameter for controlling the resonant frequencies. The problem has been solved using method of moments (MoM) and the numerical results are verified through simulation on HFSS and experimental measurements.

Fractal Apertures in Waveguides, Conducting Screens and Cavities

Introduction.- Method of Moment Formulation of Coupling through Apertures.- Fractal Frequency Selective Diaphragms in Rectangular Waveguide.- Electromagnetic Transmission through Fractal Apertures in Conducting Screen.- Radiation from Rectangular Waveguide-Fed Fractal Aperture Antennas.- Investigations on Cavity-Backed Fractal Aperture Antennas.- Conclusions and Future Work.

Design of a gain enhanced THz bow-tie photoconductive antenna

This paper presents design of a high gain conventional bow-tie photoconductive antenna in the THz frequency band. Simulation results of the proposed antenna are presented in this paper. The paper also deals with the effect of silicon lens on the antenna radiation pattern which enhances the directivity of the antenna by a considerable amount.

A CRLH substrate integrated waveguide leaky wave antenna based on Hilbert slot

This paper presents a novel design of leaky wave antenna based on composite right/left handed (CRLH) substrate integrated waveguide (SIW). The design uses the space filling property of Hilbert fractal slot to realize the CRLH response. The slot dimensions are designed in such a way that both the left hand and right hand band operate well below the waveguide cut off frequency which provide a greater level of miniaturization. The main lobe direction of the radiation pattern can be steered from backward to forward direction with a change in frequency. Simulation results for both the input reflection coefficient and radiation patterns are presented in the paper.

Substrate integrated waveguide slot array for millimeter-wave space applications

In this paper SIW slot array is designed for W band applications using low temperature co-fired ceramics fabrication (LTCC) techniques. SIW corporate feed network was designed using SIW T and Y junction power dividers and SIW 90° bend and operated over 86 GHz to 94 GHz. The antenna is fed using GCPW-SIW transition which operates over the entire W band. The 8×8 slot array has been simulated and the impedance bandwidth is found from 87.5 GHz to 90.5 GHz with a gain of around 15dB over the entire band.

Method of Moment Formulation of Coupling Through Apertures

This chapter presents a mathematical formulation of several class of aperture coupling problems between two arbitrary regions through multiple apertures. The formulation is based on the “Generalized network formulation for aperture problems” which is solved using the Method of Moments (MoM). Mainly two different classes of basis functions namely roof top basis function and RWG functions are used in the analysis in order to model regular and arbitrary shaped apertures, respectively. The excitation matrix is formulated assuming waveguide fundamental mode and the uniform plane wave excitation. The aperture characteristics are expressed in terms of the scattering parameters, aperture admittance and transmission cross section.

Investigations on Cavity-Backed Fractal Aperture Antennas

This chapter investigates the properties of probe fed cavity backed fractal aperture antennas. The problem is formulated using the finite element-boundary integral (FE-BI) method in which the field inside the cavity is formulated using the finite element method and the mesh is truncated at cabity apertures surface using the boundary integral method. Several dual-band cavity backed fractal aperture antennas based on Sierpinski gasket, Sierpinski Carpet, plus shape fractal and Minkowski fractal are investigated. The numerical results obtained from the FE-BI code have been validated with simulations on HFSS.

Radiation from Rectangular Waveguide-Fed Fractal Aperture Antennas

The properties of fractal apertures fed by rectangular waveguide has been investigated in this chapter. The self similarity and space filling properties of fractal geometries are exploited to achieve multiband radiation. Some self-affine fractal geometries suitable for waveguide fed apertures, have been proposed and investigated. It is shown that the scale factor of the fractal geometries can be used as a design parameter for controlling the resonant frequencies. The problem has been solved using method of moments (MoM) and the numerical results are verified through simulation on HFSS.