基于全相位FFT的感应式磁力仪频谱校正方法研究

基于法拉第电磁感应定律的感应式磁力仪是用于测量低频磁场的空间探测仪器,常具有在轨FFT频谱分析功能,直接获得波动磁场的频率及幅度等信息.利用FFT方法对截断信号进行计算时,整周期采样会产生频谱泄露和栅栏效应,频谱信息产生偏差,而影响实时监测磁场变化的准确性.全相位FFT与常规FFT相比,有相位不变性和良好的抑制频谱泄露能力.采用基于全相位FFT的时移相位差方法(apFFT/apFFT)校正在研的某卫星感应式磁力仪直接采集的波形数据.仿真和实验结果表明,apFFT/apFFT方法可有效提高感应式磁力仪低频磁场测量的频谱准确性.研究工作为提高感应式磁力仪科学数据的应用水平奠定了基础,为下一代星载感应式磁力仪在轨频谱分析提供了一种可能的新方法. 

Research of Spectrum Correction Method Based on All Phase FFT for Induction Magnetometer

Induction magnetometer,based on Faraday's law,is used to measure the magnetic field changes with low frequency in space.It usually has the function of on-orbit FFT spectrum analysis, which can obtain the information of magnetic field fluctuation directly,such as frequency and amplitude.However,when using FFT to process the truncated signal,non-complete period sampling will cause spectrum leakage and fence effect.Namely the spectrum information will generate deviations, which affects the accuracy of real-time monitoring of magnetic field changes.Compared with traditional FFT,the all-phase FFT with phase invariability can effectively prevent spectrum leakage.In this paper,an all-phase time-shift phase difference method (apFFT/apFFT) is used to correct the aveform data of a satellite induction magnetometer.Simulation and experimental results indicate that this method can improve the measurement accuracy.This study also provides a method about on-orbit spectrum analysis for the next generation of spaceborne induction magnetometer.