Novel Design Method for Grading Honeycomb Radar Absorbing Structure Based on Dispersive Effective Permittivity Formula

In this letter, we present a novel design method, which is based on the dispersive effective permittivity formula, to carry out the coating thickness optimizations of grading honeycomb radar absorbing structure (RAS). First, the calculation model for the reflectivity of honeycomb RAS is established by using the dispersive closed-form effective permittivity expression and the transmission line theory. Then, the comparison between calculative results and experimental data shows that the computational error of reflectivity can be reduced by about 75% with the introduction of dispersive formula. Finally, the coating thickness of a grading honeycomb RAS is optimized by using this computation method. The fractional bandwidth of 141.2% is realized for at least 10-dB reflectivity reduction under normal incident. Furthermore, the total thickness in terms of that at the lowest cutoff frequency decreases by 43.2% and the thickness-to-bandwidth ratio increases by 128.5% compared to the grading honeycomb RAS in the literature. A good agreement between calculated, simulated, and measured results demonstrates the validity of this optimization.