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Energies 2018, 11(10), 2586; https://doi.org/10.3390/en11102586

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

1
Key Laboratory of Photoelectric Logging and Detecting of Oil and Gas, Ministry of Education, Xi’an Shiyou University, Xi’an 710065, China
2
The Oil Production Technology Research Institute of the First Oil Production Factory of the Chang Qing Oil Field, Yan’an 716000, China
*
Author to whom correspondence should be addressed.
Received: 20 August 2018 / Revised: 13 September 2018 / Accepted: 24 September 2018 / Published: 28 September 2018
(This article belongs to the Section Energy Fundamentals and Conversion)
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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. View Full-Text
Keywords: pseudo random sequence; impulse response of the earth; correlation identification; anti-noise performance pseudo random sequence; impulse response of the earth; correlation identification; anti-noise performance
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Song, X.; Wang, X.; Dong, Z.; Zhao, X.; Feng, X. Analysis of Pseudo-Random Sequence Correlation Identification Parameters and Anti-Noise Performance. Energies 2018, 11, 2586.

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