Wideband Electrical Characteristics of Small-Diameter Instrumentation Cables in Seawater

摘要

Certain oceanographic applications exist where it is desired to transmit data over an electrical cable from sea depths of ten to twenty thousand feet. Mechanical handling-packaging and streaming considerations limit cable diameter, yet impose severe strength requirements. In addition, the amount of information to be transmitted dictates a large bandwidth requirement. The propagation characteristics of several possible cables was analyzed theoretically, considering the effects of seawater. Accurate values of attenuation and characteristic impedance was determined by IBM-7090 computations and are presented graphically over the frequency range from ten cycles to one megacycle. The inclusion of steel in cables for strength was studied for its effects on electrical characteristics. All cables showed wide parameter variations with frequency, therefore the suitability of a representative cable for transmission of digital signals was briefly investigated. Insofar as receiving amplifier and cable noises allow, a method of countering waveform degradation by proper cable equalization is shown. (Author)