半航空瞬变电磁干扰特征与降噪研究

为了验证多旋翼无人机在半航空瞬变电磁勘探作业中产生的电磁干扰影响，笔者等开展了一系列实验，包括在无人机不同工作状态下进行时频噪声分析，以及研究噪声源与接收点之间距离对噪声水平的影响。实验发现，大疆T20无人机电机转动产生的周期性电磁干扰频段在550~900 Hz，当接收线圈与无人机的距离为10 m时此干扰可被忽略。针对剩余的其他噪声，笔者等提出了基于移动窗口的递归最小二乘法自适应降噪方法。通过降噪实验，验证了该方法能够有效压制干扰，还原出信号的原始特征。将此降噪方法应用于香格里拉安乐铅锌矿实测半航空瞬变电磁信号处理，取得了显著的降噪效果。

Study on semi-airborne transient electromagnetic interference characteristics and noise reduction

To verify the electromagnetic interference effects of multi-rotor UAV in semi-airborne transient electromagnetic exploration, and develop effective noise reduction methods to improve the quality of exploration signal data.Methods: The time-frequency noise analysis is carried out to detect the electromagnetic interference generated by multi-rotor UAV (taking DJI T20 as an example) under different working conditions.The influence of the distance between the noise source (UAV) and the receiving point on the noise level is studied.A recursive least square method based on moving window is proposed and applied.Results: It is found that the main frequency band of periodic electromagnetic interference generated by motor rotation of DJI T20 UAV is 550~900 Hz.When the distance between the receiving coil and the UAV is 10m, the above interference can be ignored.Noise reduction experiments prove that the proposed adaptive noise reduction method can suppress the interference effectively and restore the original characteristics of the signal.Conclusions: It is proved by experiments that the electromagnetic interference of multi-rotor UAV in semi-airborne transient electromagnetic exploration can be observed, especially at close range.By applying recursive least square method based on moving window, the electromagnetic interference generated by UAV can be effectively reduced and the original characteristics of the disturbed signal can be restored.The application of the noise reduction technology to actual geological exploration data processing can significantly improve the data quality, and is conducive to further geological interpretation and mineral resource evaluation.