An Ultra-Thin Polarization Insensitive Microwave Absorber with a Transmission Window

This paper presents an ultra-thin microwave absorber with a transmission window on a low-cost substrate material. The unit cell of the proposed absorber consists of metallic cross dipole patch on top plane and a ring slot at the conductive bottom plane. The substrate height is 0.8 mm, which is ultrathin. The low profile ultra-thin planar structure makes it valuable for electromagnetic interference (EMI) reduction at 5.9 GHz which is industrial, scientific and medical (ISM) frequency band and a transparent window at 4 GHz (C-band). The surface current distributions on the top and bottom planes are studied to elaborate the absorption and transmission mechanism of the structure. The orthogonal symmetry of the structure makes it polarization insensitive and hence suitable for realization in real time environment. The measured results are verified with the simulated ones to test its performance and found to be similar.