| With the rapid development of oil drilling technology,intelligence and information technology has gradually become a new development trend,which has higher requirements for pressure,torque and the real-time performance of the relevant parameters in the formation during drilling,as well as for the efficiency of data transmission.Wireless electromagnetic communication is one of the most effective transmission methods at present,but the data transmission reliability of this method is easily affected by the electromagnetic characteristics of formation media.This paper focuses on the above problems and carries out the simulation analysis of near-drill electromagnetic wireless transmission method and transmission characteristics.According to the results,a near-bit wireless electromagnetic transmission and receiving system with low noise,low power consumption and simple structure is designed.The specific work is as follows.(1)In view of the attenuation characteristics of electromagnetic wave propagation in the lossy medium,receiving coil in MATLAB in the influence factors of induced electric field intensity on the simulation analysis,at the same time in the SIMULINK near-bit wireless electromagnetic transmission channel model is established,and through this channel model of BPSK modulation signal demodulation method is developed for the calculation of the bit error rate,The improved coherent demodulation BPSK demodulation algorithm is proposed.Compared with other algorithms,it has the advantages of high reliability and simple implementation structure.(2)In the design of the receiving system,the hardware circuit is designed based on the characteristics of weak induction signal amplitude and low signal to noise ratio(SNR)of the receiving coil,and the designed bandpass filter circuit is optimized for noise,so that it has a better processing effect on low SNR signals.(3)This paper completes the concrete implementation of the improved coherent demodulation algorithm,including hardware circuit design and software program design.Its structure is relatively simple,which greatly reduces the complexity and power consumption of the system.Finally,a magnetic antenna test model is built indoors to debug and test each functional module of the system.When the communication distance is 4m,the data demodulation accuracy of the receiving system can reach 99.97%,which meets the expected design requirements. |
