覆盖X和Ku波段的低雷达散射截面人工磁导体反射屏∗

摘要

设计并制备了一种基于人工磁导体(artificial magnetic conductor, AMC)的覆盖X和Ku波段的宽带低雷达散射截面(radar cross section, RCS)反射屏.将双频带耶路撒冷十字形AMC结构和宽带双金属方形AMC结构复合,通过参数优化,使耶路撒冷十字形结构的反射相位反转频点与方形结构的反射相位零值频点重合或者非常接近,进一步扩宽有效相位差区域,从而拓展RCS减缩带宽.给出了反射能量峰值方位的一般理论计算公式,当入射角度、棋盘单元尺寸和观察频率确定后,可通过公式计算出反射峰的方位. HFSS软件仿真结果与理论计算结果符合较好,验证了理论公式的正确性.同时与等尺寸金属平板相比,在7.4—17.0 GHz 频带内,除9.8 GHz附近的少数频点外,天线后向RCS均有−10 dB以上的减缩,基本覆盖X波段和Ku波段,相对带宽为78.7%,在11.6 GHz时,减缩量最大,达到40.3 dB.加工了反射屏实物并进行测试,测试结果与仿真结果基本一致,证实了反射屏具有宽带的低RCS特性.%Based on the properties of the artificial magnetic conductor (AMC), a broadband low radar cross-section (RCS) reflection screen covering X and Ku band is designed and fabricated. The reflection screen is formed by combining two AMC cells, i.e., AMC1 with a dual band Jerusalem cross structure, and AMC2 with a wideband metal square patch structure. By optimizing the structures of these AMC cells, it is achieved that the frequency corresponding to the inversion point of the AMC1 reflection phase curve is equal or close to the frequency corresponding to the null point of the AMC2 reflection phase curve. Therefore, the valid reflection phase difference band is broadened and the RCS is reduced in a wider band. In addition, presented in this paper is a theoretical formula to calculate the reflection energy peak direction. When the incident angle, chessboard unit dimension and observed frequency are fixed, the reflection energy peak direction can be calculated by the formula. The calculation results from the theoretical formula are consistent with the HFSS simulation results, so the theoretical formula is valid. The simulation results indicate that, compared with the same-dimension metal RCS, the backscattering RCS is reduced by more than 10 dB in a frequency range of 7.4–17.0 GHz, except minority frequencies close to 9.8 GHz. The 10 dB-reducing RCS bandwidth covers the entire X band and most of Ku band, and the relative bandwidth is 78.7%. The largest reduction reaches 40.3 dB at 11.6 GHz. The simulations and the measurements are in good agreement. The results validate the broadband low RCS property of the reflection screen.