A Polarization-Independent Tunable Microwave Absorber with Wide Tuning Range

In this paper, a tunable microwave absorber has been presented for L-band applications. The proposed design consists of square loops which are connected through varactor diodes across the diagonals. By controlling the reverse voltage of the varactors, the absorption frequency can be tuned for a wide frequency range. The novelty of the proposed design lies in its four-fold symmetry, which makes the structure polarization-insensitive unlike the earlier reported tunable absorbers. Furthermore, a prototype of the proposed structure has been fabricated where the active components are regulated using a novel biasing technique. The measured results also show good agreement with the simulated responses under normal incidence as well as for different polarization angles.