Ultrasonic Through-thick-wall Communication Based On Adaptive Equalizer And Energy Harvesting

The thesis presents a design of ultrasonic through wall communication system with self-adaptive method and energy harvesting. The ultrasonic wave has strong ability to penetrate in the thick-metal-wall. Without the influence of electromagnetic shielding, the ultrasonic carrier signal is very suitable for special environment. A high speed ultrasonic communication is achieved with the help of echo cancelling technology.By analyzing the characteristics of ultrasonic transducers, such as, structure implementation, resonance frequency and impedance matching. The ultrasonic transmitting and receiving structure was optimized for high energy transfer efficiency. According to the characteristics of ultrasonic transmission in the channel, this paper puts forward a guiding adaptive equalization method for the echo cancellation. An adaptive filter based on LMS(Least Mean Square) is used to identify the ultrasonic channel. The echo cancellation operation can be accomplished on the FPGA. This algorism is design on the System Generator. The high order filter can be drawn automatically by parametric package implementation. Under the guidance of simulation, the design is optimized by setting parameters of the mask.The inside-wall module has a demand of self-powering. A super-capacitor is very suitable for this requirement. A power management circuit is designed to protect the super-capacitor, and manage the power supply. The inside and outside wall system are designed respectively. The outside-wall transmitter uses the digital signal generator based on FPGA to generate a digital wave. A DAC(Digital to Analog Converter) transfer the digital wave into an analog signal. The signal can be enhanced by the pre-amp and power-amplifier. On the other hand, the outside-wall receiving module magnifies the signal and converts it into digital signal. The inside-wall module is optimized for low power consumption with a MSP430 microcontroller.Finally, after the simulation, the hardware circuit is designed for this system, and successfully verified through a testing. The transmit rate could achieve up to 70 kbps.