Bharoti Sinha

A study on the behaviour of M-type barium hexagonal ferrite based microwave absorbing paints

This paper deals with development of single and double-layer microwave absorbing paints using Mn-substituted barium hexagonal ferrite. The comparative studies of both theoretical and experimental results at Ku band have been reported. It has been found that the single layer absorbing paint exhibits peak absorption of 12.3 dB at 17.4 GHz for a thickness of 1.12 mm. Double layer absorbing paint with each layer of different composition of ferrite gives a broad band characteristics, but at the cost of lowered absorption.

Development and characterization of hexagonal ferrite based microwave absorbing paints at Ku-band

This paper deals with the development of single and double layer microwave absorbing paints using Mn-substituted Barium hexagonal ferrite. The comparative studies of both theoretical and experimental results at Ku-band have been reported. It has been found that the single layer absorbing paint exhibits peak absorption of 12.3 dB at 17.4 GHz for a thickness of 1.12 mm. Double layer absorbing paint with each layer of different composition of ferrite gives a broad band characteristics, but at the cost of lowered absorption.

Development and characterization of (Ba-Mn-Ti) based hexagonal ferrite for microwave absorbing paint

This paper deals with the design, development and characterization of the hexagonal ferrite powder [Ba(MnTi)/sub x/Fe/sub (12-2x)/O/sub 19/] for x=1.6 as microwave absorbers. The hexagonal ferrite powder has been developed by a dry attrition and sintering procedure. The developed ferrite powder 60% by weight has been mixed in epoxy resin to form a microwave absorbing paint. This paint was coated on conducting aluminum sheet to study absorption characteristics of a linearly polarized TE wave at X-band. The computed result for different coating thicknesses have been reported. These paints are very useful in military applications such as RCS reduction, camouflaging of the target, prevention of EMI etc.

Transmission line modeling (TLM) for evaluation of absorption in ferrite based multi layer microwave absorber

We present the development and design analysis of a multi layer microwave absorber. Three samples of M type hexagonal ferrite powders, namely [Ba(MnTi)/sub /spl delta//Fe/sub (12-2/spl delta/)/O/sub 19/] for /spl delta/ = 1.6, 1.7 and 1.8, have been developed using the dry attrition and sintering process. On the basis of the transmission line model, the microwave absorption for a three layer microwave absorber with different combinations of ferrite for an overall coating thickness of 1.5 mm have been computed. It has been found that the three layer microwave absorber with each layer of different composition provides broad band characteristics with a minimum of 10 dB absorption from 12.5 to 18 GHz. This type of microwave absorber is very useful in military application for reducing the radar cross section of the target.

Reduction in SAR using RF shields made of nickel-zinc spinel ferrite at 2.4 GHz

Abstract This paper presents the experimental evaluation of the ‘Specific Absorption Rate’ (SAR) reduction in a human head due to radio frequency (RF) shields attached to a mobile handset. Shields of various shapes and sizes were made from a nickel–zinc spinel ferrite. The human head was simulated by a fibre glass container filled with NaCl solution to represent the muscle tissues. An E-field probe was used to measure the electric field strength at various points in the head model with and without the RF shields. The E-field variations in the head model show that the developed ferrite RF shields reduce the ‘SAR’ effectively.

Characterization of (Co-Mn-Ti) substituted M type barium hexagonal ferrite based microwave absorber at X band

This paper present the design, development and characterization of the hexagonal ferrite powder [BaCo/sub 0.5/spl delta//Ti/sub 0.5/spl delta//Mn/sub 0.1/Fe(11.87-/spl delta/)O/sub 19/] at /spl delta/=1.6 as microwave absorber. The hexagonal ferrite powder has been developed by dry attrition and sintering procedure. The developed ferrite powder 60% by weight has been mixed in epoxy resin to form a microwave absorbing paint. This paint was coated on conducting aluminum sheet to study absorption characteristics of linearly polarized TE wave at X band. The experimental and computed results for different coating thickness have been reported. It has been found that it shows the broadband characteristics with minimum absorption of 6.5 dB from 8 to 12 GHz for a coating thickness of 2 mm. These paints are very useful in military application such as RCS reduction, camouflaging of the target and prevention of EMI etc.

A Hybrid Analysis of Electromagnetic Scattering due to a Dielectric Wedge

The electromagnetic scattering and absorption due to a lossy dielectric wedge have been studied. A hybrid method combining UTD and MOM has been used to calculate the surface fields existing on the wedge contour. Both field variations i.e., interior and exterior to the wedge have been computed by solving a coupled pair of surface integral equations (SIE) arising due to the soluions of Maxwells equations with proper boundary conditions applied. Results for various wedge angles and values of σ, and for various source orientations have been presented. TM plane wave illumination has been assumed.

A Moment Method Solution for the Active- and Mutual- Admittance of Longitudinal Slots in a Rectangular Waveguide

This paper presents a moment procedure to study the admittance properties of mutually coupled longitudinal slots in the broad-wall of a rectangular waveguide. The method is attractive in that it takes into account the mutual coupling because of external fields and the internal fields due to both propagating and evanescent modes. It also incorporates, inherently, the effect of wall thickness, and utilizes the actual field distribution within the slot. The method is self-consistent, reliable, and accurate. Computed results for various slot-parameters at different offsets and various slot lengths are presented.

Diffraction Co-Efficient of a 90° Straight Dielectric Wedge with TM Illumination: A Numerical Method

This paper deals with numerical evaluation of complex diffraction co-efficient for a 90° straight dielectric wedge with TM illumination. Since diffraction co-efficients for dielectric structures are not well defined because of the severe analytical difficulties they pose, this evaluation will help to solve many physical problems untractable before. Computation shows that the diffraction co-efficient is a function of €r σ frequency and is dependent upon the position of the source and the field point.