STUDY OF GRAPHITE ABSORBERS AT MICROWAVE FREQUENCIES

Abstract

An absorber is defined by a surface which gives very small reflection when illuminated by electromagnetic source. Absorbent coatings are used on the walls of anechoic chambers and o.n the enterior surface of military aircraft and vehicles to achieve radar invisibility. The present study has been devoted to design a thin, broadband, dielectric absorbers using graphite in X-band. In chapter-2 various theories have been given to calculate 'the reflection loss at any angle of incidence, polarization and frequency. First the impedance method to calculate the reflection coefficient has been discussed. In the end of this chapter a different approach has been given to calculate reflection coefficient for normal incidence. This approach can be used to write computer program. In third chapter the approach for designing the graphite absorber has been discussed in detail. The basic material of absorber is polystyrol powders coated with graphite. The absorber has been designed in X-band (8.5-12.5 GHz) for different thicknesses of a layer. The various calculated and measured results have been discussed in chapter-5. The comparison of design method given here and converging impedance method has been discussed also. Finally a single layer absorber has been fabricated, and tested. A theoretical study of other multilayer absorbers has been given also.