The bandwidth of a single layer absorbing material

Abstract

The absorber considered in this paper consists of a single layer of lossy dielectric material backed by a good conductor. It is assumed that both the magnetic and the electric dissipation factors of the dielectric may be greater than zero. Previous work was done on this structure in which the following special cases were considered: (1) zero magnetic dissipation factor (2) zero electric dissipation factor (3) equal electric and magnetic dissipation factors. For these special cases, methods were given for determining possible values of the magnetic and electric parameters and the resulting thickness. Also considered was the possible bandwidth of the structure, and for this purpose an approximate e expression for the bandwidth was derived. This paper extends the above work to include finite but unequal electric and magnetic dissipation factors. A method is given for determining the parameters and thickness of the material. For certain combinations of electric and magnetic dissipation factors a solution is impossible regardless of the values of other design parameters. The region composed of these combinations has been determined and is presented. There are indications that the bandwidth of this structure may be large. Since the previous expression assumed a small bandwidth, it seemed desirable to examine more closely the relationship between frequency and reflected energy. The power reflection coefficient as a function of frequency is presented for several combinations of design parameters.