Combining the Wiener Filter With Calibration Device to Improve the Accuracy of the Helicopter Transient Electromagnetic System

Abstract

The transfer characteristic of the receiver sensor (TCRS) in a helicopter transient electromagnetic (HTEM) system can severely distort the measured data, especially early in the off-time. Removing TCRS is essential for an accurate and quantitative description of HTEM data. Precise Measurement and suppression of the TCRS are challenging due to measurement errors and noise in the HTEM system. We propose to use a calibration device to train the Wiener filter and then construct a TCRS deconvolution function to remove TCRS and enhance the HTEM system’s shallow detection capabilities. First, we design a calibration device and get its ideal and actual response in an existing HTEM system. Then the Wiener filter is trained using the measured and ideal response of the calibration device. Finally, we use a Wiener filter to obtain a recorded signal free of TCRS. Field tests show that the Wiener filter effectively suppresses the influence of TCRS on the recorded signal. After processing the observed signal with the Wiener filter, the blind time is reduced from 88.54 μs to 67.71 μs. The blind spot is reduced by 14.90 m for 100 Ω∙m homogeneous earth and 33.32 m for 500 Ω∙m homogeneous earth. The accuracy of the processed signals in channel two is improved by 16.93%. Accuracy for other channels is enhanced by 1.5%.