Development Of High-speed Data Transmission Circuit While Drilling

Logging while drilling technology can effectively realize the comprehensive evaluation of formation information by analyzing and processing the real-time data collected on the drilling site,so as to reasonably control the drilling trajectory and continuously adjust the drilling process.In the logging while drilling system,the transmission of data information is the core technology,which has certain constraints on the development of logging while drilling technology.In order to obtain more detailed downhole geological information as much as possible,the types of downhole parameters collected while logging while drilling are increasing,and the amount of data is becoming larger and larger,so the data transmission rate on the channel between the downhole and the surface must be improve.However,in the commonly used data transmission technology while drilling,the data transmission rate of the mud pulse method is low,which cannot meet the needs of modern drilling operations;the data transmission rate of electromagnetic wave transmission and acoustic wave transmission methods is also not fast enough and the transmission distance is also short;Pole storage transmission technology cannot transmit data in real time.How to solve the contradiction between rapidity,reliability and realtime performance has become a key problem to break the bottleneck of data transmission while drilling.A kind of magnetic induction transmission system appeared abroad can effectively solve the problem.This article studies the data transmission circuit while drilling based on magnetic induction transmission.First,the thesis analyzes the data transmission theory of magnetic induction while drilling,analyzes the transmission principle and equivalent circuit model of the electromagnetic induction coupler,and makes the magnetic induction coupler of this paper according to the coupler structure designed in the laboratory.The coupling channel has a center carrier frequency It is 1.35 MHz.And conduct in-depth research on the 2FSK carrier communication theory selected in this paper,including the study of 2FSK signal description,modulation principle and demodulation principle.These theories form the basis of this thesis.Second,design the modulator and demodulator according to the requirements of the project’s technical indicators.Based on STC15F2K60S2 MCU and DDS chip AD9832,a 2FSK modulator is designed.The modulator can modulate the digital specified by the user,or directly modulate the digital information input on the PC side,which can effectively produce a good quality 2FSK modulation signal below 10 MHz..Based on Xilinx Artix-7 series FPGA and AD acquisition chip AD9280,a 2FSK demodulator is designed.This digital signal processing demodulator has good performance and can process high-speed A/D data streams in real time.The demodulation speed and A/D The acquisition speed is synchronized and real-time demodulation of 2FSK is real-time.Finally,an information synchronization experiment based on serial port transmission was carried out.In the experiment,the two carrier frequencies of 2FSK were 1.3MHz and 1.4MHz.Even with two carrier frequencies that are so close,the demodulator designed in this paper can still demodulate in real time.Experimental results show that the transmission rate of the high-speed data-while-drilling data transmission circuit designed in this paper reaches 57.6 kbps required by the project index.The system transmission can easily realize simplex and half-duplex communication.