High bit-rate digital communication through metal channels

The need to transmit digital information across metallic barriers arises frequently in industrial control applications. In some applications, the barrier can be penetrated with wiring, while in others this may not be possible. For example, metal bulkheads, pressure vessels, or pipelines may require a level of mechanical integrity that prohibits mechanical penetration. This study investigates the use of ultrasonic signaling for data transmission across metallic barriers, discusses the associated challenges, and analyzes several alternative communication system implementations. Several recent efforts have been made to develop through-metal ultrasonic communication systems, with approaches ranging widely in bitrate, complexity, and power requirements. The transceiver designs presented here are intended to cover a range of target applications. In systems having low data rate requirements, simple transceivers with low hardware/software complexity can be used. At high data rates, however, severe echoing in the ultrasonic channel leads to intersymbol interference. Reliable high speed communication therefore requires the use of channel equalizers, and results in a transceiver with higher hardware/software complexity. In this thesis, issues related to the design of reliable through-metal ultrasonic communication systems are discussed. These include (1) the development of mathematical models used to characterize the channel, (2) application of equalization techniques needed to achieve high-speed communication, and (3) analysis of hardware/software complexity for alternative transceiver designs. Several groups have developed through-metal ultrasonic communication systems in the recent past, though none has produced a mathematical model that accurately describes the phenomena found within the channel. The channel model developed in this thesis can be used at several stages of the transceiver design process, from transducer selection through channel equalizer design and ultimately system performance simulation. Using this channel model, we go on to develop and test several ultrasonic throughmetal transceiver designs. Ultrasonic through-metal communication systems are finding use in a wide variety of applications. Some require high throughput, while others require low power consumption. The motivation for developing several designs - ranging from low complexity, low power to high complexity, high throughput - is so that the best design can be matched to each application. After these transceiver designs are developed, we present an analysis of their computational requirements so that the most appropriate transceiver can be chosen for a given application.