Increasing the capacity of an ultrasonic communication systems using variable structure control

摘要

Narrow bandwidth transducers used in existing ultrasonic (US) data communication systems are known to be devices with a high Q resonant response and low coupling to both the electrical drive and acoustic interfaces. These features limit the speed of phase change when phase modulation (PM) is used. This thesis studies the design of a Variable Structure Controller (VSC)-based transmitter and receiver with the aim of increasing the capacity of a PM-based US communications system. Simulation results are presented to demonstrate that a VSC controller can be employed in combination with US transducers to achieve the control of transducer dynamics to deliver the required transient response to allow PM symbols with a duration of three carrier periods in comparison with standard transducers. A low frequency prototype system has been constructed to demonstrate the feasibility and potential of this approach.