# Research on New Drilling Downlink Communication Based on Anisotropic Magnetoresistive Technology
## 1 Introduction
However, the weak current-carrying information in electric current field information transmission has restricted its development to a certain extent. At present, the main application occasions of electric current field information transmission are generally in underwater, mine, subway emergency communication, and other fields [15]. [PERSON] pointed out that the technology of communication by conducting electric current field was feasible, and introduced a wireless transceiver device based on electric current field communication [16]. The underwater electric conduction channel characteristics, such as the path loss and time dispersion, are obtained from a channel measurement campaign in open sea waters by [PERSON] Implications of the channel characteristics to digital communications design are discussed [17]. [PERSON] used the electric current field to realize the underground communication through the stratum, and analyzed the relationship between the field strength of the electric current field with the transmission distance and the size of the emission dipole electrode under the constant flow field electromagnetic wave propagation model [18]. [PERSON] constructed the channel model of the rock and soil layer, and proposed a specific implementation scheme of throughground communication system combining software and hardware, which provided a theoretical basis for the follow-up research [19]. In recent years, with the rapid development of electromagnetic measurement technology [20], anisotropic magnetoresistance detection technology has emerged [21; 22]. This technology is widely used in the field of non-contact weak current detection because of its high sensitivity and low cost. In view of the great advantages of anisotropic magnetoresistance technology in weak current detection, this study combines the electric current field information transmission technology with the anisotropic magnetoresistance weak current detection technology [23; 24], which greatly improves the practical operability of electric current field information transmission, and effectively makes up for the shortage of electric current field wireless communication. In this paper, the mathematical model of the current field and magnetic field distribution around the drill string is established, and the influencing factors of the current field wireless communication mode are analyzed [25] to study the information downlink communication technology with high speed and low bit error rate in the process of oil and gas resource development. At the same time, the information downlink communication system based on anisotropic magnetoresistance detection is theoretically analyzed and modeled, and the relevant experimental platform is built. Through experimental tests and analysis, the influence relationship of key parameters such as transmitting voltage, electrode spacing, and working temperature on information transmission is obtained, which provides a theoretical and technical basis for further optimizing downlink information and communication technology while drilling. Downlink Communication and Modeling of Information While Drilling Based on Anisotropic Magnetoresistance Detection  
In order to study the current distribution and magnetic field distribution around the drill string, the structure of the downlink communication system based on anisotropic magnetoresistance detection was firstly modeled. In the electric current field communication mode of injecting current on the electrode, two electrodes were connected at both ends of the transmitter as antennas, and the electrodes are in good contact with the rock and soil layer. The carrier signal (alternating voltage) carrying information was sent to the two electrodes at the transmitting end [26; 27]. The drill string is a good conductor that can be used to replace one of the electrodes to allow alternating current to flow through the drill string.