A weak and frequency-varying signal detection method for rotating magnet ranging system

Key words:  signal detection  weak and frequency-varying signal  frequency reconstruction  discrete Fourier transform (DFT)  rotating magnetic field  rotating magnet ranging system (RMRS)

Abstract:

According to the weak and frequency-varying characteristics of rotating magnetic signal, a filtering method was developed based on discrete Fourier transform (DFT) double-peak spectrum value. Firstly, the frequencies of two peaks in the main-lobe of signal amplitude spectrum were searched. Secondly, the initial frequency value was reconstructed based on the two frequencies and the true frequency value was solved by Newton 's method. Finally, the signal amplitude was recovered. The proposed method was tested by computer simulation and outdoor experiments. The simulation results show that the double-peak method is much better than the single-peak method based on DFT. The experimental results agree well with the variation law of magnetic field strength with distance. The proposed method is proved to be effective and accurate. The method can track the varing frequency accuratly and extract the weak amplitude precisely.