Design and Analysis of Frequency Selective Rasorber Based on Square-Loop Arrays with Lumped Resistors

A multi-layer frequency selective rasorber (FSR) consisting of two cascading metallic layers separated from one another by three thin dielectric substrates is proposed in this paper. The top absorbing layer and bottom transmitting layer are a periodic array of square loops, while the lumped resistances are loaded in the middle of the four sides of the top square loop array constituting the absorption layer. The bottom square loop array transmits waves in the working frequency band and acts as a metal ground within the absorption band. Thus, the designed absorber will achieve transmission/absorption characteristics at low and high frequencies respectively. The simulated and measured results show that the proposed absorber has a 1 dB transmission band below 1.43 GHz and a 10 dB absorption bandwidth spanning from 7.05 GHz to 10.21 GHz.