Frequency-Selective Rasorber Based on Square-Loop and Cross-Dipole Arrays

A novel design of a transmission window within the absorption band of a circuit analog absorber, named as frequency-selective rasorber (FSR), is presented. Based on an equivalent circuit model, the conditions are formulated to produce a passband with small insertion loss and to reduce the reflection at frequencies below and above the passband in the meanwhile. Simple design guidelines of our proposed FSR are then developed. With loaded lumped elements, the arrays of square-loop and cross-dipole are combined to realize its implementation. It is shown through measurements that an insertion loss of 0.68 dB can be obtained at 4.42 GHz and the fractional bandwidth for at least 10 dB reflection reduction within the lower and upper frequency bands is 92.3% under the normal incidence. A good agreement between simulated and measured results validates our design.