Analysis of time-varying channel effects on transmission performance of deep-sea abandoned measuring instrument

Abstract

Because of the environmental requirements, deep-sea abandoned measuring instrument mostly uses the cable channel. However, the stability of the channel transmission is seriously affected by length change in electrical impedance of the channel. In this paper, a new method is presented, which is used for dynamically analysing the effects of the cable channel on the amplitude and phase of the transmission signal by using XCTD (expendable conductivity, temperature and depth) profiler transmission channel. Firstly, regulations about the parameters of each circuit varying with the channel length is proposed. Meanwhile, the simplified transmission circuit model and its transfer function are established. Through qualitative analysis we can conclude that the transmission frequency, distributed capacitance and winding inductance have an influence on the signal phase. Finally, in this paper we analyse and discusse how the cable influences the transmission of signal, and present the reason of the influences with MATLAB, which can further guide the design of the XCTD measuring system and improve the accuracy of the measurements and the stability of signal transmission.