高频磁耦合有缆钻杆信道建模与仿真分析

高频磁耦合有缆钻杆能够提高随钻测量数据的传输速率,其使用同轴电缆减少信道的高频损耗,利用磁耦合感应实现钻杆之间的无线信号传输。为了确定信号载波频率、实现不同有缆钻具间的阻抗匹配以及降低信道衰减,使用2种不同模型完成了信道建模与仿真分析。首先使用标准二端口网络元件级联模型仿真,虽然基于测量数据的"黑箱"网络元件无法给出物理解释,也没有用于优化的设计参数,但仿真结果有利于有缆钻杆工艺改进的验证性实验。其次使用集总参数电路和传输线混合模型仿真,其中集总参数电路有可测量的设计参数,在提供物理解释的同时能够优化设计,而传输线仿真了高频条件下长度不能忽略的同轴电缆。混合模型使用分级网络的链接参数完成散射参数的计算,设定了耦合系数、绕组电感及磁滞损耗3个调谐参数,仿真结果与测量结果相吻合。

Channel modeling and simulation of high-frequency magnetic coupling wired drill pipe

High-frequency magnetic coupling wired drill pipe can increase the transmission rate of MWD (measurement-while-drilling)data, able to use coaxial cable for reducing high-frequency loss and realize wireless signal transmission between drill rods based on magnetic coupling effect. To determine the signal-carrier frequency, achieve the matching impedance between different wired drilling tools and reduce channel attenuation, two different models are utilized to complete the channel modeling and simulation analysis. Firstly, the cascade model of standard two-port network elements is used for simulation. Although the "black box" network element based on measurement data is unable to give physical explanation, and also cannot provide optimized design parameters, the simulation results are beneficial to the verification experiment of wired drill pipe process. Secondly, the hybrid model combining lumped-parameter circuit and transmission line is applied for simulation; the lumped-parameter circuit has measurable design parameters, able to provide physical explanation and optimize the system, and the transmission line simulates the coaxial cable with the length unable to be ignored under high-frequency conditions. In the hybrid model, the scattering parameter is calculated by the link parameters of cascade network, so as to set three tuning parameters (coupling coefficient, winding inductance and hysteresis loss). The simulation results are exactly consistent with those measured data.