Research On Ultra Long Distance And High Speed Communication System In Borehole Radar

As a branch of ground penetrating radar,borehole radar detects underground formation information by transmitting electromagnetic waves.Compared with the ground penetrating radar used on the ground,the downhole radar works thousands of meters underground,which has the advantage that it is difficult to replace.With the development of downhole radar imaging technology,the amount of uploaded data continues to increase.In the past,the low data transmission rate and limited working depth were gradually unable to meet the demand,which restricted the development of the downhole radar system.The research on long-distance high-speed communication system of borehole radar has become an urgent problem to be solved in borehole radar logging.In order to realize the high-speed communication of borehole radar in deep wells,the design and implementation of the ultra-long-distance high-speed communication system of borehole radar are analyzed and studied in the thesis.The main work is as follows:Firstly,the working principle of the borehole radar is analyzed.In view of the advantages of strong anti-interference ability and high frequency band utilization of Orthogonal Frequency Division Multiplexing（OFDM）technology,the route of adopting OFDM modulation technology for the borehole radar communication system is finally determined.Secondly,according to the engineering requirements,the hardware circuit of the radar communication system in the well is designed.The deep underground environment is complex,and the performance requirements of components are high,which increases the difficulty of hardware circuit design.In order to achieve long-distance high-speed transmission and reception of data.An hardware circuit scheme is proposed,which takes the FPGA as the core and works with a variety of peripheral circuit modules.And the hardware circuit design of each module of the radar communication system in the well is completed.Next,based on the FPGA platform,the thesis completes the design and simulation of the digital circuit of the sending and receiving link of the ultra-long-range communication system of the borehole radar.In order to realize long-distance communication,it is necessary to adopt the technology of signal coding and modulation to reduce errors.On the basis of determining the overall FPGA logic design scheme,the design modeling and implementation of the baseband link on the FPGA are studied in depth.And the FPGA of the main digital circuit modules of the transmitter and receiver of the radar communication system in the well is introduced in detail.Model design,FPGA implementation,and simulation results,including: scrambling and descrambling,convolutional coding and decoding,channel interleaving and de-interleaving,Quadrature Amplitude Modulation（QAM）modulation and demodulation,pilot insertion,FFT/IFFT transform,and cyclic interval insertion,etc.And thesis simulates the system in Vivado to verify the correctness of the signal processing flow.Finally,after completing the design of the hardware circuit and digital circuit of the ultra-long-distance high-speed communication system of the radar in the well,the hardware debugging and system testing of the circuits and functional modules such as power supply,clock,data transmission and acquisition and reception links on the hardware system are carried out,which proves that the design and function of all module of the system are correct and feasible.