Polarisation-independent tunable absorber with embedded biasing network

A polarisation-independent tunable absorber has been presented with wide tuning range. The proposed design consists of periodic patterns of square loops connected through varactor diodes, thus resulting in tunable performance. Due to four-fold symmetric design, the structure exhibits tunable characteristic for all polarisation angles unlike the earlier reported tunable absorbers. Furthermore, the configuration also eliminates the need for any external biasing network, and therefore avoids the design difficulties associated with the added bias grids. A prototype of the proposed structure has been fabricated, whose measured results show good agreement with the simulated responses under normal incidence.