Nawal K Agrawal

Broad Band Thin Sheet Absorbers for S-; C-; X- and Ku-Bands

The design procedure for a single layer thin sheet microwave absorber which exhibits broad band characteristics is described in this communication. Using the proposed design approach, single layer absorbers of thickness less than 7mm in S-band, 5mm in C-band, 4mm in X-band & 3mm in Ku-band to give a minimum 1OdB absorptions over their entire respective bands, have been theoretically designed. Barium Hexa-ferrite as the radar absorbing material and rubber as binderare used in the design. Based on the design detail, a thin sheet absorber for entire Ku-band operation has been fabricated and tested. The practically obtained results for absorptions agree very closely with the theoretically predicted values. This order of absorptions and bandwidth were so far achieved by the use of multilayered absorbers rather than a single layer as in proposed design. These types of absorbing sheets are very useful in military applications for reducing radar cross section.

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.

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 Radial Cylindrical Surface Wave Antenna

A new type of surface wave antenna utilizing an unsymmetrical radial surface wave is proposed in this communication. The antenna consists of an inductively reactive surface coincident with the ρ-plane of a cylindrical co-ordinate system. This surface is confined between two conducting vertical walls. The surface wave field propagating radially outward in such a structure is studied inside the antenna. The on-axis gain of such an antenna is calculated theoretically and compared with experimentally observed value. It is found that such an antenna has several desirable features.