In this study, a broadband radar absorbing sandwich composite (BRASC) with stable absorption performance for oblique incidence is proposed to reduce radar cross-section (RCS) of an engine inlet. To design the BRASC, the objective function for broadband absorption performance is coupled with transmission line theory. The absorption bandwidth of the designed BRASC with a − 10 dB criterion is 8.2 GHz. The absorption performance of the oblique incidence in both transverse electric and transverse magnetic polarizations is excellent in maintaining the −10 dB up to 60°. The measurement results of the fabricated specimens confirm that the overall tendency of the measurement results matches well with the analysis results. The engine duct replaced with the BRASC is analyzed to confirm the effect of RCS reduction on the engine inlet. RCS simulation shows that the proposed BRASC effectively reduces the RCS over a wide frequency range. Because the S-shaped duct, which is used in low observable aircraft for RCS reduction, causes multiple scattering at oblique incidence, the absorbers applied to the engine duct should maintain a stable oblique incidence performance. Hence, the proposed BRASC may be a promising candidate for engine inlets with small RCS.

中文翻译：

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斜入射吸波性能稳定的宽带雷达吸波夹层复合材料及其在发动机风道中的应用以降低RCS

在这项研究中，提出了一种对斜入射具有稳定吸收性能的宽带雷达吸收夹层复合材料（BRASC），以减少发动机进气道的雷达截面（RCS）。为了设计 BRASC，宽带吸收性能的目标函数与传输线理论相结合。设计的 BRASC 的吸收带宽为 - 10 dB 标准为 8.2 GHz。在横向电极化和横向磁极化中斜入射的吸收性能在保持 -10 dB 至 60° 方面非常出色。制作试样的测量结果证实，测量结果的总体趋势与分析结果吻合良好。对更换为 BRASC 的发动机管道进行分析，以确认 RCS 减少对发动机进气口的影响。RCS 仿真表明，所提出的 BRASC 在很宽的频率范围内有效地降低了 RCS。由于在低可观测飞机上使用的 S 形管道用于减少 RCS，在斜入射时会产生多次散射，因此应用于发动机管道的吸收器应保持稳定的斜入射性能。因此，所提出的 BRASC 可能是具有小 RCS 的发动机进气口的有希望的候选者。