Research On Signal Transmission Based On Acoustic Carrier In Solid Medium

This paper presents the design of a signal transmission system using ultrasonic as the carrier wave and a solid medium as the medium.This system is designed for the situation that traditional electromagnetic wave communication and cable communication is not good and inconvenient to implement when in the electromagnetic shielding and sealing environment and other special circumstances.The main work of this paper is as follows:Firstly, the basic propagation characteristics of sound waves in solid and the characteristics and matching problems of ultrasonic transducers are analyzed to ensure the system can be achieved and operated stably. According to the transmission characteristics of ultrasonic waves in the channel, the causes of signal transmission interference caused by multipath reflection effect are analyzed, and the system and channel model are established by analyzing the whole signal transmission system and channel.Then, the design and implementation of the hardware and software system of the ultrasonic signal transmission system is completed by taking the transmission characteristics of the acoustic wave in the solid.The hardware platform is based on STM32 and it includes the ultrasonic transducer drive circuit module, the signal processing circuit module which takes the protection circuit, the filter circuit and the signal decision circuit as the core, and the peripheral circuits such as the power supply circuit and the debugging interface. The development of software system is completed through MDK integrated development environment, including the design of system operation control and condition monitoring software module, signal sending software module and signal receiving software module.In order to improve the quality of signal transmission and reduce the interference during signal transmission, the secondary sound wave cancellation method based on system identification and equalizer and the modulation and demodulation system design based on binary frequency shift keying (2FSK) are summarized by referring to the traditional digital communication technology.Finally, the function and performance test of the signal transmission system was performed when the hardware and software of the system were debugged. The test results show that the system hardware circuit and software design is reasonable and feasible, and can complete the low-speed signal transmission in the high purity nylon rod by 500bps or less by ultrasonic loading signal.The research work completed in this paper provides the hardware and software platform for the further research work, and it has the potential of the follow-up development.