Key Technologies Research Of Marine Electromagnetic Signal Acquistion

In recent years, petroleum as an important strategic resource is becoming more and more important, with the intensification of the international situation and the development of national economy. Oil and gas resources exploration technology on land and in near-coast has been developed, but exploration technology under deep sea is still in its infancy. In order to the country’s long-term safety, mining of oil and gas exploration technology in deep sea needs to develop urgently.This paper belongs to the national high technology research and development program (863 program) marine controllable source underwater system equipment development and theory research. The core task is to develop marine electromagnetic data recorder, making our country have the capability of oil and gas exploration in deep sea.For the many problems of marine electromagnetic signal acquisition, this paper launchs on soft demodulation technology, automatic gain amplification technology, electrode range and circuit path zero’s automatic compensation technology based on FPGA. This paper has completed the three technologies’design effort of scheme design, hardware design and software design, and the relevant functional tests.This paper achieves the function of signal soft demodulation. The premiere condition of soft demodulation technology is analyzed:the ADC clock source and the FPGA logic clock source must be the same. The principle of soft demodulation technology is analyzed in the form of waveform, and the ADC sampling driven design, synchronization design between sample and modulation, data recovery are designed. Differences from hard demodulation, soft demodulation can avoid the principle of demodulation of the effects on signal channel’s background noise.This paper achieves the function of signal automatic gain amplification. The necessity of marine electromagnetic data acquisition automatic gain amplification is analyzed. This paper has designed the hardware circuit of automatic gain amplification, and has completed information extraction of the signal peak-to-peak value, automatic gain control algorithm and drive logic of gain control in software design.This paper also has implemented the function of automatic compensation for electrode range and circuit path zero. This paper analyzes the disadvantages of the existence of electrode range and circuit path zero, the principle of compensation, the hardware is designed as the closed loop control system’s actuator for the electrode range and circuit path zero compensation. The software design has completed the information extraction of electrode range and circuit path zero, the design of the compensation algorithm and drive logic.