机载数字化设备屏蔽效能的提高

Improvement of shielding effectiveness of airborne digital equipment

为了降低机载数字化设备的电磁波辐射发射强度,对数字信号的频谱进行分析,指出数字信号所包含的基波及其高频谐波是设备电磁辐射的源头;分析了屏蔽层抑制电磁辐射的机理,结果表明高电导率、非磁性屏蔽层对电场及高频磁场有很好的屏蔽效果;研究了缝隙对屏蔽体屏蔽效能的影响,提出了一种提高缝隙屏蔽效能的双层填充屏蔽方法;然后分析了电磁波通过屏蔽层时的吸收损耗,提出了一种提高双绞屏蔽电缆/同轴电缆屏蔽效能的双层屏蔽方法;最后以实际工程项目为例,该项目设备已满足GJB151B-2013 RE102要求的情况下,仍然干扰北斗设备搜星定位。对它进行电磁兼容改进,改进后实验室测量RE102项,设备电磁辐射发射强度平均降低约12 dBμV/m;外场地面及飞行实验结果表明,设备正常工作情况下,BDB1,BDB3频点的带内积分功率分别提高0.59 dBm和1.84 dBm,北斗设备收星数量由3颗及以下上升至9颗及以上,北斗设备可正常定位。

To reduce the electromagnetic radiation emission intensity of airborne digital equipment,the spectrum of the digital signal is analyzed,revealing that the fundamental wave and its high-frequency harmonics are the sources of electromagnetic radiation emissions.Next,the rationale of shielding layer to suppress electromagnetic radiation is analyzed.The results indicate that the high-conductivity non-magnetic shielding layer has a good shielding effect on the electric field and high-frequency magnetic field.The influence of the gap on the shielding effectiveness of the shield is analyzed again,and a new method of doublelayer fill shielding is proposed and validated.Then,the absorption loss of the electromagnetic wave is analyzed,and a new method for improving the shielding effectiveness of twisted-pair shielded cable/coaxial cable double-layer shielding is proposed and validated.Finally,an actual engineering project is considered as an example.The project equipment satisfies the GJB151B-2013 RE102 requirements and still interferes with the Beidou equipment Star(BDS)Searching and positioning.The electromagnetic compatibility is improved using the proposed method.After the improvement,the emission intensity of electromagnetic radiation is significantly reduced,by 12 dBμV/m on average.The ground and flight experiments verify that the integral power of the BDB1 and BDB3 frequency points is increased by 0.59 and 1.84 dBm,respectively,under normal operating conditions,and the number of BDS searching satellites is increased from≤3 to≥9,the BDS can operate normally.