Design Of Downlink And High-efficient Power Amplifier Of The High-speed Data Transmission System Based On Single-core Logging Cable

At present, the difficulty of oil exploration and gathering is growing, much more information underground should be processed, and the logging system becomes further complex. As a typical production logging tool, single core cable logging system is widely used due to its small size and low cost. However, the limited available frequency band of single core cable restricts the transmission rate of system in the well logging, and the downhole system should be designed to have a higher stability because of the high temperature and pressure environment.The thesis from the actual needs of logging discusses the high-speed data transmission system, which is an important part of single core cable logging system, and analyzes some key factors restricting the transmission rate and reliability. Then the author proposed an improved scheme according to the characteristics of single logging system. The main contents are as follows.1.Describes the frequency characteristics of single-core cables, and states the characteristics and transmission method of dounlink data. The thesis uses 2FSK, which simplifies the circuit structure and reduces the interference in the system, to replace the original baseband transmission. The downlink transmisson rate of the system increases from 300 bps to 610 bps.2.Analyzes the principle of ? ?? DAC, and switching rate characteristics of MOS in power amplifier. The thesis implements the module in heat resisting FPGA to replace the 12 bit DAC in original system. The new part could generate the PWM signal to drive the backend efficient digital amplifier, and reduce the OFDM signal peak-to-average power ratio(PAPR).3.Builds a drive circuit and H-bridge circuit with 10 MHz switching frequency, a differential low-pass filter. The efficiency of the power amplifier reaches 86%. In addition, the system was tested in high temperature environment. The result showed that the system bit error rate was kept low, and uplink rate reached 350 Kbps.Above design improves system performance, promotes the development of single logging system, and contributes to similar studies in other fields.