Analysis of Pseudo-Random Sequence Correlation Identification Parameters and Anti-Noise Performance

Xijin Song, Xuelong Wang, Zhao Dong, Xiaojiao Zhao and Xudong Feng
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Xijin Song: Key Laboratory of Photoelectric Logging and Detecting of Oil and Gas, Ministry of Education, Xi’an Shiyou University, Xi’an 710065, China
Xuelong Wang: Key Laboratory of Photoelectric Logging and Detecting of Oil and Gas, Ministry of Education, Xi’an Shiyou University, Xi’an 710065, China
Zhao Dong: The Oil Production Technology Research Institute of the First Oil Production Factory of the Chang Qing Oil Field, Yan’an 716000, China
Xiaojiao Zhao: Key Laboratory of Photoelectric Logging and Detecting of Oil and Gas, Ministry of Education, Xi’an Shiyou University, Xi’an 710065, China
Xudong Feng: Key Laboratory of Photoelectric Logging and Detecting of Oil and Gas, Ministry of Education, Xi’an Shiyou University, Xi’an 710065, China

Energies, 2018, vol. 11, issue 10, 1-18

Abstract: Using a pseudo-random sequence to encode the transmitted waveform can significantly improve the working efficiency and depth of detection of electromagnetic exploration. The selection of parameters of pseudo-random sequence plays an important role in correlation identification and noise suppression. A discrete cycle correlation identification method for extracting the earth impulse response is proposed. It can suppress the distortion in the early stage of the excitation field and the glitches of the cross correlation function by traditional method. This effectively improves the accuracy of correlation identification. The influence of the order and the cycles of m-series pseudo-random coding on its autocorrelation properties is studied. The numerical results show that, with the increase of the order of m-sequence, the maximum out-of-phase periodic autocorrelation function decreases rapidly. Therefore, it is very beneficial to achieve synchronization. The limited-cycle m-sequences have good autocorrelation properties. As the period of the m-sequence increases and the width of the symbol decreases, the overall autocorrelation becomes closer to the impact function. The discussion of the influence of symbol width and period of m-sequence on its frequency bandwidth and power spectral density shows that the narrower the symbol width, the wider its occupied band. The longer the period, the smaller the power spectral line spacing. The abilities of m-sequence to suppress DC (Direct-current) interference, Schumann frequency noise, and sine-wave noise are analyzed. Numerical results show that the m-sequence has excellent ability to suppress DC interference and Schumann frequency noise. However, for high-order harmonic noise, the correlation identification error appears severe oscillation in the middle and late stages of the impulse response. It indicates that the ability of m-sequence to suppress high-frequency sinusoidal noise is deteriorated. In practical applications, the parameters of the transmitted waveform should be reasonably selected in combination with factors including transmitter performance, hardware noise, and ambient noise level to achieve the best identification effect.

Keywords: pseudo random sequence; impulse response of the earth; correlation identification; anti-noise performance (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
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