Читать книгу Introduction To Modern Planar Transmission Lines - Anand K. Verma - Страница 252

The lossy DNG slab can also be used as a perfect absorber, in place of the metasurface and resistive screen combination. The DNG slab absorber is developed around two configurations shown in Fig (5.17). Figure (5.17a) shows the lossy DNG slab with a conductor backing, and Fig (5.17b) shows it without any conductor backing. The working principle of a lossy DNG slab absorber is completely different. However, it is not based on the negative refraction property and backward wave nature of the DNG medium.

The characteristic impedance of any magneto‐dielectric slab, DPS or DNG, is computed as . The impedance matching with free space could be achieved μ_r(ω) = ε_r(ω). Such natural DPS materials are not available. However, μ_r(ω) and ε_r(ω) of a DNG slab are engineered using two different structures. So both μ_r(ω) and ε_r(ω) can be tuned independently to obtain their equalization at the same frequency. Thus, impedance matching could be realized in a DNG slab. If a DNG slab is sufficiently lossy, then absorbed RF power could be dissipated in the DNG slab of appropriate thickness.

Figure 5.17 Free space matched lossy DNG absorber.